EXPLAINING MAYA MONUMENTAL ARCHITECTURE

A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAI‘I AT MĀNOA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF

MASTER OF ARTS

IN

ANTHROPOLOGY

MAY 2012

By Nancy Sack

Thesis Committee:

Terry Hunt, Chairperson Christian Peterson Jay Silverstein

TABLE OF CONTENTS

LIST OF TABLES ...... iii

LIST OF FIGURES ...... iv

CHAPTER 1. EXPLAINING CULTURAL ELABORATION ...... 1

CHAPTER 2. THE MAYA LANDSCAPE ...... 15

CHAPTER 3. MAYA CLIMATE AND AGRICULTURE ...... 26 Climate ...... 26 Water management ...... 36 Agriculture ...... 38 Summary ...... 45 CHAPTER 4. MAYA POPULATION ...... 47

Population size and density ...... 47 Bioarchaeological research ...... 54 Migration ...... 55 Demographics ...... 56 Diet ...... 58 Health ...... 60 Summary ...... 61 CHAPTER 5. DISCUSSION AND CONCLUSIONS ...... 63

APPENDIX A. Dates of initial and final dated monuments by site ...... 73

APPENDIX B. Lake Chichancanab climate data ...... 77

APPENDIX C. Population growth in selected lowland Maya sites ...... 84

REFERENCES ...... 85

ii LIST OF TABLES

1. Elements of the bet-hedging model ...... 11

2. Ancient Maya cultural periods ...... 19

3. Number of sites building dated monuments ...... 23

4. Late Classic Maya population estimates ...... 50

iii LIST OF FIGURES

1. Map of known Maya settlements ...... 18

2. Number of sites concurrently building dated monuments ...... 24

3. Cumulative number of sites with dated monuments ...... 25

4. Percent sulfur in Lake Chichancanab core ...... 31

5. Percent calcium carbonate in Lake Chichancanab core ...... 32

6. Percent δ18O in Lake Chichancanab core ...... 33

7. Population growth (continuous occupation) ...... 51

8. Population growth (cyclical occupation) ...... 52

iv CHAPTER 1. EXPLAINING CULTURAL ELABORATION

The task of archaeologists is to infer the cultural processes at work in the (often distant) past, based on an examination of the artifactual, biological, and environmental evidence of human civilizations that remains today. Ancient monuments, like other cultural constructions, can reveal clues about the societies that created them, provided researchers ask suitable questions and devise appropriate strategies for discovering the answers. Initial archaeological surveys of monumental buildings are typically designed to answer “what” types of questions: investigators describe, measure, and map the structures they uncover.

The next generation of research generally deals with “how” questions, for example, how were monuments built? How long did it take to construct them? How much labor was required? How did the buildings function? Eventually, archaeologists begin to explore the more difficult “why” questions. Why did ancient societies begin to construct monuments?

Why did monumental construction persist, in some cases for hundreds of years? Finally, why did monument building decline and disappear?

Archaeologists have historically considered immense public architecture to be a hallmark of ranked or stratified societies because its construction is assumed to reflect a ruler’s ability to recruit a large labor force. As a consequence, archeological research has often sought to account for the emergence of social complexity, rather than monumental architecture itself.

Evolutionary archaeologists view monumental architecture “as an aspect of the archaeological record requiring explanation rather than simply as an indicator of a particular level of social organization” (Kornbacher and Madsen 1999:241). This paper examines the extent to which an evolutionary model of cultural elaboration known as bet hedging can

1 account for the development, distribution, and persistence of Maya monumental architecture.

In the 1980s archaeologists began to explore life history theory, a part of evolutionary ecology, as an explanatory model for cultural change. According to life history theory, organisms can invest their energy in growth, maintenance, and reproduction, but energy allocated for one purpose cannot be used for another. Fertility is the most important component of an organism’s fitness (Kaplan and Lancaster 2003). Because the amount of energy devoted to growth and maintenance affects fertility, the strategy an organism employs can be understood as a tradeoff between current and future reproduction and between the quantity and quality of offspring (Hill & Kaplan 1999; Kaplan and Lancaster 2003). An organism can only contribute to the gene pool if its offspring and their offspring also reproduce. Should reproductive fitness decline to zero in any generation, an organism’s progeny will disappear from the population. Because population increase is multiplicative rather than additive, an energy budget that maximizes an organism’s long-term geometric- mean fitness, even at the expense of its short-term arithmetic-mean fitness, will have an evolutionary advantage (Seger and Brockmann 1987).

The optimal allocation of an organism’s energy budget will always be constrained by genetic and environmental factors (Shennan 2002). Natural selection will favor the strategy that results in the highest average success rate in a particular environment. In stable environments with ample resources, an organism’s best strategy to pass on its genes to future generations is to maximize the number of offspring it produces. In certain situations, however, a more successful strategy is to sacrifice some short-term reproductive success as a hedge against future catastrophe. Lower-than-expected fertility will increase an organism’s

2 long-term fitness as long as three conditions are met: (1) periods of population growth are punctuated by recurrent population crashes caused by calamities such as widespread food shortages; (2) a strategy is available that improves the probability of survival during periods of food scarcity but it requires that resources be diverted from reproduction; and (3) the long-term benefit of the ability to survive a demographic crisis equals or exceeds the benefit of investing the same energy in producing more offspring during periods of growth (Boone and Kessler 1999).

Researchers have determined that in temporally varying environments the trade-off is an evolutionary advantage: statistically, the cost of producing fewer offspring in good years is outweighed by the long-term benefit of increased survival in lean years. Seger and

Brockmann (1987:185) refer to this type of trade-off as “bird in the hand” bet-hedging. The strategy will be evolutionarily stable only if the population of strategy followers is protected from invasion by mutants, i.e., those with a different strategy (Grafen 1999). Organisms that produce too few offspring might allow a mutant to invade, so the stable strategy is to populate each environmental state—the lean years and the productive years—with enough offspring that the strategy can survive “attack.”

Variable environments also select for polymorphism, that is, genotypes that can express different phenotypes, including cultural traits, depending on conditions. This is the kind of bet-hedging that Seger and Brockmann (1987:185) call the “don’t put all your eggs in one basket” strategy. With polymorphism, a proportion of offspring is adapted to thrive in good years (that is, to produce more offspring in the next generation), while a different proportion is adapted to survive in lean years (i.e., to produce fewer offspring). This type of bet hedging still requires a sacrifice of short-term (second-generation) fitness and may actually increase

3 the risk of failure, but the payoff is even greater geometric-mean fitness (i.e., a larger number of offspring in the third and subsequent generations). In areas of both spatial and temporal variability, high migration rates tend to favor greater polymorphism. Migration itself becomes a bet-hedging strategy because “a genotype that distributes itself over the available environments (by migrating) will average its fitness in much the same way as one that distributes itself over the available phenotypes (by diversifying)” (Seger and Brockmann

1987:195, emphasis in the original). Abundant empirical evidence indicates that plants, birds, and humans are capable of adjusting their energy allocations in response to environmental conditions—over short- and longer-term intervals—so as to maximize their reproductive fitness (e.g., Boone and Kessler 1999; Kaplan and Lancaster 2003; Voland 1998; Wood

1990).

Evolutionary mechanisms also play a role in the choice of mating partners. Zahavi (1975,

1977) investigated sexual selection in an effort to understand why males would evolve characteristics seemingly detrimental to survival such as deer antlers, peacock plumes, or bird coloration and song, and why females would evolve preferences for males that displayed those attributes. He proposed that those outwardly disadvantageous traits are actually markers of quality: the presence of the marker in the phenotype is proof that a handicap was imposed and overcome, so it serves as a sign of superior fitness. Grafen (1990) has demonstrated mathematically that so-called costly signaling and a preference for organisms that invest in costly signaling are both evolutionarily stable strategies.

The idea that evolutionary processes apply to cultural as well as biological change has existed for more than a century (e.g., Cavalli-Sforza 1986; Cziko 1995). Darwin himself understood that the basic elements of evolution—variation, competition, and differential

4 reproduction—occur not only among biological species, but also in cultural phenomena. In

The Descent of Man (1871:60-61) he noted people’s preference for “novelty and fashion” in language, and asserted that “[t]he survival or preservation of certain favoured words in the struggle for existence is natural selection.” Scottish philosopher Alexander Bain, English economist W. Stanley Jevons, American mathematician Chauncey Wright, and Austrian physicist Ernst Mach were among the late nineteenth-century thinkers who suggested that

Darwinian selection seems to account for the trial-and-error manner in which the human brain arrives at new insights (Cziko 1995:134-141). Karl Popper likened the cumulative growth of scientific knowledge to a process of selecting fit hypotheses and the eliminating unfit ones. Scientific theories, Popper believed, are not inferred from a wealth of experiences and observations; they are conjectures based on specific, initial observations that are tentatively accepted until they are refuted or amended by subsequent observations (Campbell

1974).

The transmission of cultural traits bears a strong resemblance to the spread of infectious diseases. Both may proceed vertically (from parent to child), horizontally (between unrelated individuals of the same generation), and obliquely (among non-related individuals of different generations). Cultural traits may spread from a single person to a number of others; conversely, multiple transmitters may influence an individual, a phenomenon commonly known as social pressure. One-to-many transmission often results in significant random drift in cultural change, while vertical transmission and social pressure tend to preserve cultural traits over time (Cavalli-Sforza 1986; Henrich 2004). Because of the opposing tendencies of invention and imitation, cultural knowledge may be more changeable or more static over time than biological characteristics. The diffusion of successful innovations between

5 unrelated individuals tends to take the form of an S-curve, much like the spread of epidemics

(Cavalli-Sforza 1986).

In his influential work The Selfish Gene, Richard Dawkins (2006; first published in 1976) coined the term “meme” for the cultural equivalent of a gene. Memes, he wrote, are units of imitation that are propagated between people when they share ideas or pass on knowledge, whether intentionally or not. Dawkins suggested that selection can act on memes as it does on genes, and account for the evolution of cultural traits. Expanding on Dawkins’s idea,

David Hull (2001), a biologist and philosopher of science, developed a “general account of selection” to explain cultural evolution. Consistent with Darwinian principles, Hull described evolution as a two-step process of replication and interaction. Imperfect replication gives rise to variation in the population. Because the replication process is iterative, any variants that arise will cumulate from one successive replication to the next throughout the lineage.

Variant replicators that cause interactors to be better adapted to their environment are more likely than others to be perpetuated. In cultural evolution the replicators may be ideas or technological innovations or even the behavior of neurons, while the interactors may be individuals or groups. Just as Darwin was able to develop the evolutionary theory of biology before Mendelian genetics had been discovered, a compelling case can be made for cultural evolution even in the absence of a complete understanding of cultural transmission (Cavalli-

Sforza 1986; Hull 2001; Mesoudi et al. 2004).

While there may be no consensus about the nature of a meme, or the mechanism by which it is copied, scholars in a wide range of academic disciplines have examined cultural and other non-genetic changes as evolutionary processes. Hull (2001), for example, offered evolutionary accounts of antibody production and operant learning and Cziko (1995)

6 reviewed evidence for selection processes in brain development, memory, and education.

One practical application of evolutionary theory outside the discipline of biology is in computer programming. So-called genetic algorithms generate random solutions to complex problems, “mate” them with one another, introduce random mutations, and then select the most successful “offspring” in hundreds of iterations. By 1992, such programs had been employed in applications as diverse as image compression, game-playing strategies, broom balancing, and backing a truck into a loading dock (Cziko 1995:246). Programmers have recently used genetic algorithms to design a telescope lens and a NASA satellite antenna

(Keats 2006).

One approach to incorporating evolutionary principles in archeological explanation, known variously as behavioral ecology or evolutionary ecology, focuses on the selection for diverse phenotypes that was noted by Seger and Brockmann (1987). According to behavioral ecology, the capacity to weigh costs and benefits and to modify behavior accordingly will have a selective advantage in unpredictable environments (Shennan 2008). The ability to determine whether to cooperate or compete, for example, may have evolved, in part, in response to spatial and temporal variability of resources. In areas of predictable and plentiful resources, there may be little to gain by trading or engaging in hostilities (Nolan and Cook

2010); in regions where agricultural potential varies spatially and temporally, risk management strategies such as increased cooperation may be more successful (Allen 2004).

If it is less costly to advertise an honest willingness to cooperate with others than it is for rivals to falsify a cooperative signal, costly advertising will have an evolutionary advantage

(Henrich 2004). In areas where agricultural yields are spatially constrained, competitive strategies will have a selective advantage because the benefit of exclusive access outweighs

7 the cost of defense (Field 2003). Natural selection will also favor defensive posturing, as long as the signal is honest. In temporally variable environments, the construction of monumental architecture and the practice of competitive feasting are strategies that may increase fitness because they serve to warn competitors not to attack (Bird and O’Connell 2006; Neiman

1997).

Other archaeologists have focused less on selection for behavioral plasticity than on changes over time in the magnitude and distribution of archaeological phenomena (Boone and Smith 1998; Madsen, Lipo, and Cannon 1999; Shennan 2008). Their approach is based on the “bird in the hand” strategy of producing fewer offspring in uncertain environments.

One of the predictions of evolutionary archaeology is that “wasteful” behavior, that is, behavior not directed toward reproduction, will confer an evolutionary advantage in temporally variable environments because the short-term decline in fecundity will be rewarded by increased long-term reproductive fitness (Dunnell 1989, 1999). The notion of waste thus satisfies Boone and Kessler’s (1999:259) second condition for the evolution of lower fertility rates: it is a strategy “that increases the probability of survival through a crash but that, to implement, requires diverting resources away from producing more offspring.”

To test the waste hypothesis, Madsen et al. (1999:268) created an agent-based computer simulation that “allows the dynamics of selection to emerge through the natural interactions between agents and objects representing their environment.” The simulation demonstrated that a fluctuating environment was indeed capable of selecting for investment in “wasteful” behavior, or cultural elaboration. Simulated populations that invested more in cultural elaboration contained a higher proportion of living adults to juveniles and a larger percentage of mature adults in death assemblages, both signs of a lower birth rate.

8 Simulating alternative bet-hedging strategies such as storing food and migrating to more productive environments attenuated the selective advantage of cultural elaboration but did not eliminate it entirely, suggesting that sedentariness is not required for waste to be favored in an unpredictable environment.

The emergence of stratified societies may also be explained in evolutionary terms. In small, egalitarian societies individuals are generally self-sufficient; each member of the group has essentially the identical knowledge and skills. In larger societies, people become more interdependent and function more as integrated groups, making individuals’ fitness increasingly more dependent on the survival of an entire community. Because “individuals no longer carry the full ‘code’ for reproducing the human phenotype, including its behavioral component,” selection becomes progressively more effective at the group level than at the individual level (Dunnell 1980:65-66). At the same time, the selection for altruism based solely on kinship relations starts to disappear. Gene-culture coevolution theory explains that the strength of group-level selection for behavioral traits such as cooperation is greatest in temporally and spatially variable environments (Richerson, Boyd, and Henrich 2010) and can occur even in the absence of an evolutionary benefit to individual participants (Chudek and

Henrich 2011).

The need to manage risk is one mechanism by which functional interdependence may arise. Pooling resources is an effective buffering strategy particularly in uncertain environments, and the more widely the resources are shared, the greater the potential benefit becomes (Nolan and Cook 2010). Communities that increase in size and develop centralized control of food storage and distribution will have a selective advantage over others because those strategies reduce the chance of catastrophic shortfalls in lean years (Allen 2004; Nolan

9 and Cook 2010). Social complexity is therefore more likely to arise in regions that experience high temporal and spatial variability in crop yields than in areas of plentiful and reliable resources (Nolan and Cook 2010). In a sense, hierarchy itself becomes a form of cultural elaboration.

Status building is energetically costly behavior that diverts resources from reproductive activity. Because high status is meaningless if has no effect on other members of the society, any investment in striving for status must be accompanied by an investment in advertising

(Boone and Kessler 1999). Self-aggrandizing displays of conspicuous consumption and seemingly altruistic behaviors such as hosting lavish feasts both serve to advertise power. In variable environments those investments pay off because the short-term energy costs are likely to be rewarded by the longer-term benefit of better access to resources in good years and in times of scarcity (Boone 1998; Boone and Kessler 1999). While the outward appearance of self-aggrandizement may be the accumulation of wealth and prestige, an ultimate evolutionary consequence of such behavior is the increased ability to survive a population crash. High-status individuals may themselves believe that they are simply vying for prestige. As Boone and Kessler (1999:273) noted, “some of the costs of social advertising … in the form of acquisition and display of luxury goods and special privileges— seem to ‘feel’ like benefits rather than costs.”

The bet-hedging model predicts that investment in cultural elaboration will appear earliest and most frequently in areas of temporal environmental variability and relative resource scarcity, particularly when opportunities for migration, storage, and trade are limited. In such environments, bet-hedging behaviors have a selective advantage because they divert energy from reproduction, increasing the likelihood that the population will

10 survive widespread crop failure. Sacrificing short-term reproductive fitness should be reflected in an aging population, as indicated by fewer infant and subadult remains in burial assemblages relative to the number of mature adults. To test the bet-hedging model in an archaeological context, evidence is needed on temporal and spatial variability in agricultural productivity, demographic changes over time, and the appearance of cultural elaboration

(Madsen 2001). The empirical expectations and data requirements of the model are outlined in Table 1 below.

Table 1. Elements of the bet-hedging model. EXPECTATIONS DATA REQUIREMENTS Measures of agricultural productivity Cultural elaboration appears earliest in areas (rainfall, soil type, etc.) compared with of environmental uncertainty cultural elaboration in time and space Population growth is constrained Population estimates over time Cultural elaboration is reflected in reduced Age-at-death figures in burial assemblages birth rate and increased life expectancy over time and space

Archaeologists have evaluated the bet-hedging model at a number of locations around the globe. Sterling (1999) assessed the implications of the model in Egypt, where the amount of arable land each year depends on the degree to which the Nile River overflows its banks and deposits silt in the flood basin. Egyptian farmers enjoyed a long period of relatively consistent high flooding until about 3300 BCE, when river volume began to fluctuate and decline. The pyramids at Saqqara and Giza were constructed between 3000 and 2600 BCE, shortly after the onset of the more variable flood conditions. Also consistent with the expectations of the bet-hedging model were data from burial assemblages that indicated a decrease in juvenile mortality and an increase in adult longevity between the Predynastic

(3800-3090 BCE) and Dynastic (2100 BCE to 300 CE) periods. Kornbacher (1999) investigated the relationship between construction activity and environmental variability in

11 western Peru, home to the earliest known monumental architecture in the New World.

Reconstructions of El Niño events indicate that the area was affected by increasingly frequent floods and droughts after about 3200 BCE. Monument building activity began between 3100 and 2700 BCE, soon after environmental conditions had begun to fluctuate.

The earliest and most elaborate constructions were located in the most circumscribed settlements of the southern coast, where mobility was limited.

Hunt and Lipo (2001, 2011) applied the cultural elaboration bet-hedging model to the evidence from Rapa Nui and Hawai‘i. Investment in monument building on Rapa Nui was considerable, yet the island was notably poor in natural resources and its geographic isolation made migration difficult or impossible. The island was subject to frequent droughts, and agricultural productivity depended almost entirely on unpredictable rainfall. Paleo- demographic evidence indicated that the age distribution of the population was skewed to the right, that is, there was a greater percentage of older adults and a smaller percentage of pre-adults than would be expected in more favorable environmental conditions. On the

Hawaiian Islands annual rainfall varies both temporally and spatially, with leeward areas having the most erratic rainfall patterns. Hunt and Lipo (2001) found that the construction of heiau, whether they were measured by total area or simply counted, was nearly always higher in leeward areas than in windward areas. Age-at-death data again showed a right- skewed distribution, consistent with the predictions of the bet-hedging model.

Aranyosi (1999) examined the distribution of monumental structures in Ireland. He found that the majority of megalithic monuments and passage grave complexes were located in areas of limited agricultural productivity that had steep slopes, poor drainage, high altitudes, and/or shallow soil depth. Hamilton (1999) demonstrated that bet hedging could

12 account for mound building in the lower Mississippi Valley. The mounds she examined had been constructed between 6000 and 2000 BP, following the onset of the El Niño Southern

Oscillation (ENSO), which brought higher variability in rainfall and more frequent flooding to the region. In a departure from the typical study on the origin and persistence of cultural elaboration, Dunnell and Greenlee (1999) investigated the disappearance of earthworks construction in Ohio Hopewell during the Late Woodland period. They suggested that the

“collapse” could be attributed to an increase in carrying capacity or in environmental predictability, either of which would have selected against wasteful behavior. Evidence does exist for warmer and/or wetter climate conditions at end of Hopewell, but data on population size and distribution are lacking.

For a number of reasons the classic represents a particularly interesting test case for the evaluation of evolutionary models of cultural elaboration. First, many Maya monuments built during the Classic period literally date themselves. More than 100 lintels, stelae, staircases, and other stones carved on or near monumental buildings bear exact dates of dedication. Second, there is an enormous corpus of paleobiological, paleoenvironmental, and archaeological data about the Classic Maya. In a recent review article examining Maya discoveries of the previous decade, Joyce Marcus (2003) cited 700 publications and noted that “a frustratingly large number of discoveries had to be omitted” (Marcus 2003:71). Third, in a study that proposed an evolutionary model for Maya monumental architecture, Neiman

(1997) showed that monument building ceased first in areas of the Maya lowlands that had the highest rainfall, while in locations with less rainfall, monument construction continued for up to 200 years longer. Neiman viewed Maya investment in monumental architecture as an example of the evolution of wasteful advertising. He reasoned that sending an honest

13 signal of competitive ability would serve the interests of the sender and the receiver because it would allow each of them to avoid costly warfare over access to resources. In order to eliminate the possibility of a counterfeit signal but discourage more investment than required to succeed, selective pressure would favor wasteful advertising “at a level that just exceeds the level that inferior competitors can afford” (Neiman 1997:270). If the monuments were wasteful advertising, investment in monumental construction would be expected to increase as resources become scarcer or less reliable, exactly as the bet-hedging model predicts.

14 CHAPTER 2. THE MAYA LANDSCAPE

In the years since John Lloyd Stephens and Frederick Catherwood (Stephens and

Catherwood 1854) first encountered the monuments of Copán, scores of intrepid explorers, millions of curious tourists, and hundreds of researchers have visited the palaces, temples, and pyramids of the ancient Maya cities. Stories about divine rulers who commanded legions of workers to build great ceremonial centers have captured the imagination of both the general public and the scholarly community. The discovery that the ancient Maya had an advanced understanding of astronomy, a sophisticated calendrical system, and especially, a complex written language, earned them their distinction as the most “civilized” people of the ancient New World (Cowgill 1961; Morley 1946:259). Just as intriguing as the considerable accomplishments of the ancient Maya is the mystery of their disappearance: the notion that at the height of its glory, the civilization suddenly collapsed, its great cities abandoned and the land nearly emptied of its population.

Since the early twentieth century, archaeologists have surveyed and excavated dozens of

Maya settlements, and geologists and climatologists have collected vast amounts of data in the region. Over the decades, the techniques they employed and the tools they used became increasingly sophisticated, and with each generation of Mayanists, new trends in archaeological research changed the focus of scholarly inquiry. The early archaeologists viewed the Maya as a peaceful society, scattered across the countryside in low-density rural settlements, which engaged in long-fallow milpa agriculture and observed rituals in largely vacant ceremonial centers (Morley 1946). Surprising to many researchers was the fact that the ancient Maya settlements seemed to be located in areas considered poor for agriculture.

One archaeologist (Meggers 1954) even argued that the Classic Maya culture must have been

15 introduced from elsewhere because the lowlands had such limited agricultural potential. That view was quickly refuted (Altschuler 1958), and scholars have since demonstrated the continuity of the Maya occupation and have determined categorically that the Maya civilization developed in situ.

The earliest descriptions of the Maya lowlands are of an utterly inhospitable environment

(Hammond and Ashmore 1981). Thompson (1954:25) noted that “the central core of the

Petén and adjacent regions is [sic] singularly deficient in natural resources, and the soil is scant except in the valleys.” Rathje (1971:275) later commented:

The southern Maya lowlands present a largely redundant environment which does not possess the potential for major internal symbiotic regions or for irrigation. In fact, the interior of this region is uniformly deficient in resources essential to the efficiency of every individual household engaged in the Mesoamerican agricultural subsistence economy … Yet, in the core of this rain forest region, the basic elements of Classic Maya civilization first coalesced.

The early paradigm was so ingrained, according to some researchers, that evidence of intensive agriculture was often ignored and estimates of dense urban settlements were dismissed (Dunning and Beach 2004). Yet 20 years ago, Arthur Demarest (1992:136) observed:

…[T]he Mayas raised their cities and ceremonial centers in seeming contradiction to ecological rationality and achieved their florescence in a dense, subtropical rain forest with generally thin and poor soils, unstable fresh-water supplies, few navigable rivers, and less environmental diversity … than their highland neighbors.

That view was echoed by Hansen et al. (2002), who noted that the Maya built major

Preclassic settlements in the Mirador Basin, an area that lacked fresh water, and seemed to avoid the perennial lakes to the west. Weiss-Krejci and Sabbas (2002) likewise mentioned that the northeast Petén population centers were located far from permanent water sources.

16 It is now recognized that the Maya occupied an ecologically diverse area covering the

Yucatán Peninsula of modern and extending into present-day , , El

Salvador, and western . The Pacific coastal plain in the south, with its fertile soil and plentiful marine food sources, was home to some of the earliest permanent settlements in Mesoamerica (Sharer 2006). The highlands to the north of the coastal plain are a volcanic area above 1000 meters in elevation, with good, deep soil and a rich variety of mineral resources including obsidian and jadeite. To the east of the highlands lie the lowlands of the

Petén-Yucatán peninsula, a limestone shelf with few permanently flowing rivers (Coe

1999b:16). The lowland landscape is itself a patchwork of well-drained uplands, slow-drained lowlands, and seasonal swamplands, with riverine-associated swamps located in what is today northern Belize (Dunning and Beach 2010; Fedick and Ford 1990). The seasonal swamps, known as bajos, cover between 40 and 60 percent of the land area (Dunning et al. 2002,

Sharer 2006). Today areas around bajos are considered poor land for agriculture because the clay soil becomes inundated during the rainy season and desiccated in the dry season

(Hansen et al. 2002).

Rainfall varies along a north-south gradient with as much as 4000 mm of annual rain in southeastern Belize decreasing to about 500 mm in the northwestern Yucatán (Rice 1993).

Ninety percent of the annual rainfall arrives between late May and December. The rainy season has a bimodal distribution with peaks in June and September/October (Magaña,

Amador, and Medina 1999) and a decrease in precipitation in July and August, known as the midsummer drought or canicula. The area is subject to hurricanes between the months of

August and October, which in modern times have resulted in wind damage, flooding, catastrophic crop failures, and population displacements. Historical records show that there

17 is considerable inter-annual variability in rainfall even within the southern lowlands

(Dunning and Beach 2010). In the Petén region, rainfall varies spatially and annually between

900 and 2500 mm (Rosenmeier et al. 2002). Even during the rainy season water may be scarce because much of the rainfall drains quickly through the karst surface to enter the groundwater system, and is accessible only in a few places because the water table is far below the surface (Curtis, Hodell, and Brenner 1996; Dunning and Beach 2010). Native vegetation in the Maya lowlands also displays great spatial diversity, primarily due to

Figure 1. Map of known Maya settlements (after Webster et al. 2007).

18 variability in soil moisture. High forests in well-drained soils are interspersed with grasslands in areas with poorer soil and sedges in the bajos (Rice 1993). The Maya primarily subsisted on maize, but they also raised beans, squash, chayote, bottle gourd, pumpkin, chili peppers, and tomatoes. Garden crops such as avocado and banana trees were planted in habitation areas.

Sources of animal protein included deer, peccaries, wild boar, and wild birds (Coe 1999a:58;

Lentz 1991).

Early archaeologists divided the Maya occupation into seven major periods, according to various cultural characteristics they described. The Classic period, with its monumental architecture and inscribed stelae, represented the florescence of the Maya civilization. The

Terminal Classic signified a period of decline and population collapse. The cultural-historic terms continue to be used today but have generally come to define spans of time rather than normative cultural traditions. Table 2 shows the span of years traditionally assigned to each period.

Table 2. Ancient Maya cultural periods (after Morley and Brainerd 1983). PERIOD DATE RANGE Early Preclassic 2000-1000 BCE Middle Preclassic 1000-400 BCE Late Preclassic 400 BCE-250 CE Early Classic 250-550 CE Late Classic 550-800 CE Terminal Classic 800-1000 CE Postclassic 1000-1697 (Spanish contact/conquest)

The earliest lowland Maya monumental construction appears at around 800-600 BCE at

Nakbe in the Mirador Basin, an area of the northernmost Petén region where extensive bajos cover about 70% of the surface (Hansen et al. 2002, Sharer 2006). Later in the Middle

19 Preclassic period, between 600 and 400 BCE, terraced platforms up to 18 meters high were constructed there. The first-known ball court in the Maya lowlands also dates to this period.

Carved stelae and circular and slab altars placed in front of buildings are dated to 500-200

BCE (Sharer 2006). Monumental architecture also appeared during the Middle to Late

Preclassic period at nearby Wakna, Tintal, and Xulnal (Hansen et al. 2002). During the Late

Preclassic (400 BCE to 100 CE), the largest buildings at were erected on top of the existing platforms. In the same period, temple-pyramids up to 33 meters in height and monumental architectural masks were constructed at the central lowland settlements of

Uaxactún, and at and at , in northern Belize (Coe 1999b:104).

By far the largest Preclassic center was , located about 13 km northwest of

Nakbe, and connected to it by a causeway. The immense triadic El Tigre pyramid, a central structure flanked by two smaller structures in the Western Group at El Mirador, rises to about 55 meters and covers a surface area six times that of Temple IV, the largest Classic

Period structure at (Sharer 2006). Towering over the Eastern Group of El Mirador is the Dante pyramid, the tallest and most massive Maya construction known, which climbs 70 meters above ground level and contains 2.8 million cubic feet of building material (Dunning and Beach 2010; Sharer 2006). The Lost World Pyramid of Tikal, measuring some 80 square meters at its base and rising 20 meters high, was also constructed in the Late Preclassic period (Morley and Brainerd 1983, Sharer 2006). The first so-called E groups were built at a number of Preclassic sites, including Nakbe, El Mirador, , Wakna, Uaxactún, and

Tikal. E groups comprise a western pyramid built across a plaza from an elongated platform supporting three shorter structures. The buildings were constructed so that from an observation point on the steps of the pyramid, the two annual equinox sunrises could be

20 viewed over the central structure on the platform, while the solstice sunrises appeared at the far corners of the side structures (Sharer 2006).

Major population shifts occurred at the end of the Preclassic period. Several prominent

Preclassic centers including El Mirador and Nakbe appear to have been abandoned around

150 CE and never reoccupied. Other sites such as were abandoned at the end of the

Preclassic but thrived in the Classic period (Dunning and Beach 2010). Researchers have also noted what they call the mid-Classic hiatus, a period during which monument construction temporarily ceased at several lowland Maya locations (Beach et al. 2002; Martin and Grube

2008). Some scholars have attributed the disruption in building to warfare between Tikal and

Calakmul (Dunning et al. 1999). Harrison (1977:501) believed that the hiatus may have reflected a diversion of manpower to intensive farming when swidden agriculture was no longer sufficient to feed the growing population.

The majority of Maya archaeological scholarship deals with the Classic period, spanning the years 250 to 900 CE. The Classic period saw the construction of the greatest number of monuments at the greatest number of sites throughout the lowlands. Large regional centers like , , Copán, and Tikal boasted clusters of stepped platforms arranged around courtyards or plazas. Palace buildings, expanded over the centuries by successive rulers, made up the bulk of the construction at a typical Classic Maya site, while temple- pyramids, often paired, rose high above the forest canopy. During the Classic period cities expanded substantially in size, presumably to accommodate rapid population growth. At least 3000 structures have been mapped at Tikal, the largest city, encompassing an area of about six square miles (Coe 1999b:104); the mapped area of Caracol contains over 4400 discrete structures (Chase and Chase 1998).

21 By early in the twentieth century, epigraphers were able to convert Maya Long-Count dates to the Gregorian calendar and by 1980 they could decipher and translate most Maya glyphic writing (Coe 1999a). Inscriptions and Long-Count calendar dates of dedication, which had begun to appear on Maya monuments in the Preclassic period, became more common in the Classic period. Of the 959 inscribed monuments that Morley (1938) cataloged, 450 had readable dates. Of those, he considered 65% to be absolutely reliable. A decade later, Proskouriakoff (1950), identified a somewhat smaller sample of 160 major pieces that she considered reliably dated monumental sculpture. The dates appeared primarily on stelae, but they were also carved on lintels, staircases, and other stones. The latest date on a given stela, and to a lesser extent, on other monuments, is assumed to be close in time to its inscription, particularly if it marked the end of an 1800-day cycle known as the hotun (Proskouriakoff 1950).

A number of Mayanists (Hamblin and Pitcher 1980, Bove 1981, Lowe 1985, Neiman

1997) have compiled lists of the earliest and latest Long-Count dates inscribed on Classic- period Maya structures in order to assess the temporal and spatial distribution of monument building activity. The initial and terminal Long-Count dates of monumental constructions at

92 sites, together with their Gregorian equivalents, are given in Appendix A. These data provide the basis for the figures in Table 3, which shows the number of sites beginning and ending monument construction, the total number of sites concurrently building monuments, and the total number of sites at which dated monuments had been built, over 25-year time intervals. The table shows that although the number of sites at which dated monuments were being built declined precipitously in the ninth century, construction of new monuments began at six sites between 850 and 900 CE.

22 Table 3. Number of sites building dated monuments in 25-year intervals. Date Number of new Number of sites Total Cumulative number range sites beginning ceasing monument- of sites with (CE) monument monument building sites monuments building building 250-275 0 0 0 0 276-300 1 0 1 1 301-325 0 0 1 1 326-350 2 0 3 3 351-375 1 0 4 4 376-400 1 1 4 5 401-425 2 2 4 7 426-450 2 0 6 9 451-475 4 1 9 13 476-500 2 0 11 15 500-525 3 0 14 18 526-550 0 1 13 18 551-575 2 0 15 20 576-600 6 4 17 26 601-625 6 1 22 32 626-650 2 2 22 34 651-675 5 3 24 39 676-700 6 3 27 45 701-725 3 1 29 48 726-750 4 4 29 52 751-775 10 11 28 62 776-800 16 21 23 78 801-825 4 9 18 82 826-850 4 13 9 86 851-875 5 4 10 91 876-900 1 9 2 92 901-925 0 2 0 92

The data in Table 3 are presented graphically in Figures 2 and 3. Figure 2 shows that the custom of building monuments spread across the lowlands over the course of about 650 years and peaked in the middle of the eighth century. Figure 3 is a graph of the cumulative number of lowland Maya sites at which Classic-period dated monuments have been

23 documented. The curve has its highest slope during the second half of the eighth century, when monument building was spreading at an exponential rate. The settlement area over which monument building took place was also greatest toward the end of the Classic period, between 618 and 800 CE (Lowe 1985).

Figure 2. Number of sites concurrently building dated monuments.

By far the greatest number of monuments, including the earliest ones constructed, appear in some of the least agriculturally productive parts of the landscape, rather than in the more fertile highland and coastal regions to the southwest. That pattern of Maya monumental construction is exactly what the bet-hedging model predicts. It is in temporally variable environments and in areas of limited resources that investment in “wasteful” activity confers a selective advantage.

24 Figure 3. Cumulative number of sites with dated monuments.

25 CHAPTER 3. MAYA CLIMATE AND AGRICULTURE

The bet-hedging model predicts that large public constructions are most likely to be located in areas of temporal variability and relative resource scarcity or unreliability. An assessment of the model’s applicability to cultural elaboration in must therefore consider the paleoclimate of the region, in particular the evidence for droughts; the dependence of the Maya on rainfall for crop cultivation; and the topography of the landscape and suitability of the soil for agricultural productivity. This chapter examines the research in each of those areas.

CLIMATE

Many of the studies on the Maya paleoclimate have focused on the timing and severity of episodic droughts, and a number of scholars (e.g., Gill 2000, Gill et al. 2007, Haug 2003,

Hodell et al. 1995, Hodell et al. 2005, Neff et al. 2006) have noted that acute or prolonged droughts appear to have coincided with the Preclassic abandonment, the Classic hiatus, and the Classic collapse. A substantial body of data also indicates that the ancient Maya lived in a temporally variable environment throughout their occupation of the lowlands. Not only did the region suffer frequent droughts, it was also subject to hurricanes (Dunning 2007) and volcanic eruptions (Freidel et al. 2011; Tankersley et al. 2011). Investigations of climate change in the Maya lowlands have employed a combination of retrospective and prospective approaches (Gunn, Matheny, and Folan 2002). Retrospective studies use physical evidence from the past such as ice cores, lake sediment cores, and speleothems, to reconstruct early climates. Prospective analyses, which are more process driven, examine widespread atmospheric and oceanic trends in the past and present, such as shifts in the intertropical

26 convergence zone (ITCZ), variability in the El Niño Southern Oscillation (ENSO), movement of the North Atlantic High, and fluctuations in solar emissions.

Lake core sediments provide a variety of proxy measures for local rainfall including the ratio of 18O to 16O isotopes (δ18O) in the shells of ostracods and gastropods and the

concentration of gypsum (CaSO4) and calcium carbonate (CaCO3) in the sediment. In tropical and subtropical areas, where temperatures are more-or-less constant throughout the year, the water level in closed-basin lakes is primarily affected by rainfall. Dry conditions are indicated by a higher rate of evaporation relative to precipitation; in wetter periods, rainfall exceeds evaporation. Because water containing the lighter oxygen isotope evaporates more readily, dry periods are marked by elevated ratios of 18O to 16O in the lake sediment.

Increased concentrations of gypsum are also signs of dry periods because with greater evaporation than rainfall, the volume of a lake is reduced and the saturation point of gypsum is exceeded. The gypsum diffuses throughout the lake and precipitates, where it is preserved in the sediment record. Smaller amounts of calcium carbonate in the sediment are another indication of drier conditions because gastropod shell production decreases as the water level drops.

The Maya lowlands lie within the northern boundary of the eastern Pacific ITCZ, a band of clouds near the equator that travels north in boreal summer and south in the winter.

Simulations have shown that in periods of unusual cold in the northern hemisphere, the

ITCZ tends to stay to the south, hindering the development of summer rains in

Mesoamerica (Gill et al. 2007). Central America is also affected by the North Atlantic High, a system of high pressure that is believed to contract in colder periods, migrate in a southwesterly direction, and produce drier conditions in the Caribbean area. When the

27 North Atlantic High is in the far southwest, the ITCZ is displaced to the south, increasing the potential for drought (Gill et al. 2007).

One cause of colder conditions in the northern hemisphere is a decrease in solar activity.

Solar irradiance levels can be reconstructed by measuring the relative abundance of 14C in tree rings and 10Be in ice cores (Beer et al. 2000; Van Geel et al. 1999). High solar activity shields the earth from cosmic rays, reducing the production of 14C; conversely, low levels of solar radiation allow more cosmic radiation to enter the atmosphere, producing more 14C.

Lower levels of solar radiation are also correlated with higher relative concentrations of 10Be, which is carried to the earth’s surface by precipitation. Solar variability is thought to be responsible for the well-documented 206-year cycle in the relative proportions of 14C and

10Be isotopes (Hodell et al. 2001; Stuiver and Brazunias 1993). Some researchers (Gill et al.

2007; Hodell et al. 2001) have suggested that solar forcing, i.e., changes in the level of the sun’s radiation, may have played a role in repeated Holocene droughts in the Yucatán

Peninsula. Spectral analysis of a sediment core from Lake Chichancanab (Hodell et al. 2001) indicated dry-cycle intervals of 39, 50, 100 and 810 years, as well as a particularly significant

208-year cycle. A 208-year wet/dry sequence was also discovered in a sediment record from nearby Punta Laguna (Curtis et al. 1996). The relative quantities of 18O and 14C isotopes in a

Punta Laguna core (Hodell et al. 2001) were inversely correlated over the past 2000 years, suggesting that dry conditions prevailed during episodes of increased solar activity.

El Niño is blamed for the 1983 and 1997-1998 droughts across lowland Mexico and its neighbors (Fagan 2009:172), so it is not surprising that scientists have investigated the correlation of ENSO events throughout the Holocene era with rainfall patterns in Central

America. The El Niño Southern Oscillation is a tropical Pacific oceanic and atmospheric

28 phenomenon with a cycle of between two and seven years that affects weather patterns throughout the world (Sarachik and Cane 2010:1-23). During the ENSO warm phase, temperatures in the eastern Pacific Ocean are higher than usual and there is a greater tendency for the ITCZ to linger in the south (Fagan 2009:170, Haug et al. 2001; Neff 2006).

During the cold phase, unusually low temperatures in the eastern Pacific produce the opposite effect. ENSO events began in the mid-Holocene, about 7000 years BP, and increased in frequency until about 1200 years ago (Haug et al. 2001; Moy et al. 2002).

Analysis of a sediment core from Bainbridge Crater Lake, in the Galápagos Islands

(Riedinger et al. 2002), indicated that at least 435 moderate to severe ENSO events have occurred in the past 6100 years and that both their intensity and frequency increased after

3000 years BP.

Local effects of ENSO events vary widely in their timing and magnitude (Poveda,

Waylen, and Pulwarty 2006). Precipitation data collected from over 1700 reporting stations worldwide, some from as early as 1875 (Ropelewski and Halpert 1987), show only a slight

ENSO effect in Central America. Analysis of ice core data from Quelccaya, in the Peruvian

Andes (Messenger 2002), revealed that there was no correlation between twentieth-century

ENSO events in northwestern South America and droughts in the Yucatán Peninsula.

Rainfall in Mesoamerica is influenced more by temperatures in Atlantic Ocean than in the Pacific (Enfield and Alfaro 1999). Cooler than average temperatures in the tropical

North Atlantic are associated with rainy seasons that begin later and end earlier than normal.

Cooler temperatures in the eastern Pacific extend the end date of the rainy season but have no effect on the start date. When the warm phase of El Niño is coupled with cooler tropical

North Atlantic temperatures, the rainy season in Mesoamerica tends to be unusually dry

29 (Yaeger and Hodell 2008). ENSO contributions to rainfall anomalies in Central America also seem to be subject to local orographic effects and trade wind patterns (Enfield and Alfaro

1999). During the warm ENSO phase in Costa Rica, for example, rainfall is heavier than average on the Caribbean coast and lighter than normal on the Pacific coast (Giannini,

Kushnir, and Cane 2000).

In order to test the influence of “external” factors such as solar fluctuations on climate conditions in the area of Maya settlement, Hunt and Elliott (2005) created a simulation of global climate conditions over a 10,000 year interval. Twelve droughts of varying severity occurred in the Yucatán region during the simulation period. Groundwater shortages were frequent as well, with a particularly severe case corresponding to the worst simulated drought. The authors concluded that “major rainfall deficiencies are a systematic, but irregular, characteristic of the Yucatán region” (Hunt and Elliott 2005:402). Rainfall anomalies in the Yucatán area showed little correlation with global conditions, suggesting that the Yucatán droughts were local perturbations, unrelated to the variations in sea surface temperature that modulate ENSO events. The combined effect of stochastic variations in wind currents along the eastern and western shores of the Americas seemed to be the primary influence on precipitation levels in the Yucatán Peninsula.

Reconstruction of rainfall patterns from lake sediment cores is not a straightforward process: sediment cores from lakes in the same vicinity can indicate different climatic trends.

Analysis of δ18O from a sediment core in Lake Salpetén (Rosenmeier et al. 2002) revealed that relatively dry conditions prevailed during the years 150-200, 500-550, and 850-900 CE, while a core from nearby Lake Petén Itzá (Curtis et al. 1998) indicated nearly constant ratios of oxygen isotopes at all levels. The researchers attributed the discrepancy in their findings to

30 the differences in size and depth of the two lakes; the much larger volume of water in Lake

Petén Itzá may have rendered it relatively insensitive to changes in both climate and land use.

Reconstructions are further complicated by the fact that water levels in lakes near population centers are affected by human-induced changes in lake hydrology as well as by shifts in climate conditions. Increased precipitation and increased runoff both produce lower levels of 18O in sediment cores; drier conditions and reduced erosion both result in higher δ18O signals.

Because it is difficult to separate climatic and anthropogenic effects, researchers prefer to examine sediments from lakes in the relatively uninhabited northern and central Yucatán

Peninsula, although they caution that the conditions reflected may have been quite different elsewhere in the region. Over the course of ten years, Hodell and his colleagues have

Figure 4. Percent gypsum (moving 5-point average) in Lake Chichancanab core (after Hodell et al. 1995). The raw data appear in Appendix B. 31 recovered several sediment cores from Lake Chichancanab. Selected data from the Hodell et al. (1995) sediment core are given in Appendix C and three measures—percent gypsum, percent calcium carbonate, and oxygen isotope ratio—are presented graphically in Figures 4 through 6. Figure 4 shows that the highest and the most variable levels of gypsum over a

4000-year time span occured between the years 250 BCE and 1000 CE, corresponding to the

Late Preclassic to Terminal Classic Maya periods. Figure 5 is a graph of the relative concentration of calcium carbonate between 2000 BCE and 2000 CE. The mean level is lowest between 250 BCE and 1000 CE, indicating that relatively drier conditions prevailed

Figure 5. Percent calcium carbonate (moving 5-point average) in Lake Chichancanab core (after Hodell et al. 1995). The raw data appear in Appendix B. during the so-called florescence of Maya civilization. The values for the oxygen isotope ratio presented in Figure 6 indicate that the climate became drier over a 500-year period beginning

32 around 500 BCE, and, on average, remained drier thereafter. A particularly arid period occurred in the eighth to tenth centuries, corresponding to the Maya collapse.

Figure 6. Percent δ18O in Lake Chichancanab core (after Hodell et al. 1995). The raw data appear in Appendix B.

Subsequent cores with better resolution (Hodell et al. 2001, 2005) indicated that the dry periods of the past 2500 years were each composed of multi-decadal wet/dry oscillations.

Some of the driest periods occurred between 125 BCE and 210 CE, just prior to the beginning of the Classic period. A drought in 670 CE was followed by 100 years of relatively wetter conditions. Repeated droughts occurred over the next 500 years with cycles of 213,

50, and 27 years. A dry period between 770 and 870 CE was followed by a 50-year interval of wetter conditions. Between 920 and 1100 CE the area experienced at least four additional droughts.

33 Curtis et al. (1996) found a similar pattern in a sediment core from Punta Laguna in the

Quintana Roo region of the Yucatán Peninsula. Based on the relative levels of oxygen isotopes in species of gastropods and ostracods, the authors divided the Holocene record into three distinct climatic periods. Relatively wet conditions prevailed from about 1350

BCE to 165 years BCE. During the period between 165 and 1020 CE, the intensity and frequency of dry events increased; the wettest years were equal only to the mean values from the earlier and later periods. At about 1020 CE, an abrupt return to wetter conditions signaled the beginning of the third stage, which continues to this day. That pattern is in agreement with findings from several other lake cores in Mexico and Costa Rica, and with ice core data from the Peruvian Andes. The Yucatán core also indicated that the Punta

Laguna region experienced repeated multi-decadal variations in rainfall during the late

Holocene that were superimposed on the millennial pattern. The most prominent droughts, at 585 and 862 CE, correspond to the periods of the Classic Maya hiatus and the Maya collapse.

The same sediment core was reexamined a decade later (Hodell et al. 2007), when technological advances allowed for better chronological resolution and more sensitive measures of lithographic and isotopic ratios. The analysis revealed that a particularly arid period between 535 and 550 CE was followed by a return to a relatively moist climate. A significant increase in δ18O at about 750 CE and another spike at 850 CE indicated severe droughts. Throughout the period from 750 to 1000 CE, the area experienced a wet-dry oscillation of about 50 years. A sediment core from nearby Lake Cobá also indicated a history of highly variable precipitation (Leyden, Brenner, and Dahlin 1998), although there was no sign of a Late Classic drought.

34 Climate history reconstructions from lake sediments generally rely on radiocarbon dating. The potential for calibration errors and the inaccuracy of interpolating between dated organic materials combine to produce an error rate that can be as high as ±100 years (Hodell et al. 2007; Yaeger and Hodell 2008). More reliable chronologies can be achieved with uranium-thorium and lead-210 dating techniques (Gale 2009; Hall and Henderson 2001).

Webster et al. (2007) used a combination of the three dating methods in their analysis of a stalagmite from a cave entrance at the Macal Chasm in western Belize. Examination of reflectance, color, luminescence, and stable isotopes confirmed signs of frequent and abrupt climatic changes over the past 3300 years. Relatively moist conditions were indicated during the first half of the Late Preclassic, from about 550 to 100 BCE, after which the climate became drier. A modest drought in 78 BCE was followed by more severe droughts in 5 BCE and in 141, 313, 517, 780, and 910 CE. A second stalagmite, recovered from the northwest

Yucatán and also dated using uranium-thorium, provided a high-resolution picture of climate variability over the past 1500 years (Medina-Elizalde et al. 2010). High values for δ18O indicated relatively that dry conditions prevailed during four multi-year intervals: 501-518,

527-539, 658-668, and 804-938 CE, with precipitation during those periods equal only to 36-

52% of today’s annual means. Tree ring data from millennium-old Montezuma bald cypress trees recently recovered from central Mexico indicated that droughts in 771, 810, and 860

CE were followed by a megadrought in Mesoamerica that lasted from 897-922 (Stahle et al.

2011).

Me-Bar and Valdez (2003) considered the frequency of drought events in the Maya lowlands by comparing lake core data with a random number generator they devised to produce rainfall values for 100-year intervals. The authors established three “lean” values for

35 annual rainfall (1000 mm, 1100 mm, and 1200 mm), and defined severe drought as 2-2.5 consecutive lean years; disaster, 3-3.5 lean years; and catastrophe, 4 or more years. Based on those criteria Me-Bar and Valdez estimated that, on average, the Maya lowlands experienced severe drought every 32 years, disaster every 130 years, and catastrophe every 500 years.

Because their random rainfall values were consistent with the data from lake core sediments, the authors concluded that the Yucatán droughts could be considered random.

WATER MANAGEMENT

If the Maya were dependent on rainfall for their water supply, inter-annual and inter- decadal fluctuations in precipitation would have limited their ability to produce reliable crop yields. Both the amount and the timing of rainfall are critical for a good harvest because a certain level of soil moisture is required for seed germination and maturation of crops

(Stahle et al. 2011). Kintz (1990) reported that recent milpa cultivation had failed seven out of ten years, presumably due to unpredictable rainfall. Pollen data from Lake Chichancanab suggest that maize, by far the most abundant crop in the Classic Maya period, is more sensitive than the natural lowlands vegetation to extreme fluctuations in rainfall (Leyden

2002).

Studies show that the Maya employed a variety of strategies to preserve water for the dry season and to manage excess water during the rainy season. Investigators have suggested that small depressions could have served as household water storage facilities in the northeast

Petén and northwest Belize region during the late Classic period (Weiss-Krejci and Sabbas

2002). McAnany (1990) noted that water cisterns dating to the Terminal Classic period are found throughout the Puuc region of the southern Yucatán. Such structures are unlikely to

36 have existed in the southern lowlands, however, because the water table in the area is as much as 180 meters below the surface (Siemens 1978).

At Tikal Scarborough and Gallopin (1991) found evidence for an elaborate Classic- period catchment system including six major reservoirs, which together could have provided drinking water and irrigation water for dry-season agriculture. Silverstein et al. (2009) suggested that the earthworks of Tikal, long assumed to have served as a defensive boundary, instead functioned as filtration trenches that intercepted subsurface water and directed it to catchment basins. The water collected could have irrigated dry-season crops or mitigated the effects of a canicular (mid-summer) drought. The authors noted, however, that the elaborate catchments along the north earthwork could have supported a population of only 700-1500, people, which they considered “a rather small amount in proportion to the investment of construction effort” (Silverstein et al. 2009:53).

A survey of in northwestern Belize (Scarborough et al. 1995) indicated that the

Late Preclassic and Classic Maya had constructed four drainages that could have channeled rainfall from reservoirs to the agricultural fields. At , in the Petén region of the southern lowlands, Beach and Dunning (1997) found remnants of a dam that closed off a stream to form a flat-bottomed reservoir, which would have provided a defensible source of water, plentiful enough to irrigate the nearby terraced fields during the dry season.

Numerous reservoirs, often near hilltop residences, have been documented at Caracol

(Chase and Chase 1998).

Unlike the hydraulic works in the central lowlands that were built to conserve water, constructions at Palenque and at Copán were designed to control flooding. At Palenque, a settlement located on a narrow escarpment, the Maya needed to divert excess water from

37 nine perennial watercourses generated by at least 56 streams. A team of researchers (French

2007; French and Duffy 2010; French et al. 2006) has recently found evidence of subterranean conduits, dams, drains, channels, and pools that could have directed the flow of water from the springs and perennial streams to the estimated population of 6,000 people.

The aqueducts acted as storm drains beneath the surface, to prevent the plazas from flooding, especially during the rainy season. The underground channels enabled the Maya to expand the size of their plazas by about 23% and may even have provided sufficient water pressure for a public fountain (French and Duffy 2010).

Drainage and flood control strategies were also needed at Copán, which is located on a river fed by five seasonal and perennial tributaries that often overflow their banks during the rainy season. Davis-Salazar (2006) has documented sub-structural conduits made of dressed stone that drained courtyards of the Principal Group and subterranean channels made of tuff and covered in capstones that ran under causeways and diverted water away from residences. Roof drains, also made of dressed stone and often carved with glyphs, managed runoff from elite houses and public buildings and at the same time, protected their walls and exterior sculpture.

AGRICULTURE

Conflicting evidence about agricultural productivity in the central and southern lowlands has spawned a vigorous debate among researchers about the degree to which the Maya could feed what is believed to have been a rapidly growing population. Scholars generally consider humid semitropical forests to be fragile environments with little agricultural potential that are unlikely to support the rise of complex civilizations (Cowgill 1961; Demarest 2004:4). A number of archaeologists, however, (e.g., Kunen 2001; Scarborough et al. 1995) have argued

38 that the landscape modifications initiated by the ancient Maya had transformed the southern lowlands into highly productive farmland. Some experts have noted that the Maya tended to settle on or adjacent to the best agricultural areas of the lowlands (e.g., Burnett et al. 2011 in press; Fedick 1995, 1996; Fedick and Ford 1990; Ford and Nigh 2009), while others have commented that the Maya population centers seemed paradoxically to be located in resource-poor areas lacking fresh water sources (e.g., Demarest 1992; Hansen et al. 2002;

Rathje 1971; Thompson 1954).

Prior to the start of settlement studies in the 1960s, archaeologists believed that the ancient Maya architectural complexes were vacant ceremonial centers for the ruling elite and that long-fallow, slash-and-burn milpa farming was sufficient to feed the small, widely- dispersed rural population (Chase and Chase 1998; Dunning 1996; Fedick and Ford 1990).

In the ensuing decades, as researchers found indications of sizable urban densities, they sought signs of land and water management techniques that could have supported rapid population growth. According to the “new orthodoxy” (Dunning and Beach 2004:130), the ancient Maya practiced multiple forms of extensive and intensive cultivation. Swidden agriculture, which had persisted from the Preclassic period to the Terminal Classic (Wright,

Terry, and Eberl 2009), was supplemented by terrace farming on hillsides and raised- and drained-field cropping throughout the wetlands. Later still, it became apparent that the use of those techniques was far from uniform (Fedick 1996).

There is substantial evidence that the ancient Maya altered their landscape for cultivation although scholars disagree about the relative importance of various types of agricultural systems and about the timing, pace, and scope of the anthropogenic modifications. Signs of forest clearing are apparent by 2500-2000 BCE (e.g., Leyden 2002; Pohl et al. 1996; Rice

39 1996) and coincide with the first appearance of maize pollen in sediment records (Wahl et al.

2006; Wright et al. 2009). The well-documented accumulation of thick deposits of so-called

Maya clay in many lowland lakes (e.g., Anselmetti et al. 2007; Beach et al. 2008; Dunning and

Beach 1994, Dunning et al. 1997; Hansen et al. 2002; Rice 1996; Rosenmeier et al. 2002;

Wright et al. 2009) is assumed to be the result of increased runoff caused by deforestation.

The highest rate of sedimentation occurred during the Preclassic period between 700 BCE and 250 CE, which suggests either that the Classic Maya had initiated better soil management strategies (Beach et al. 2006; Dunning and Beach 2010) or that the near depletion of the topsoil in the earlier period had left little to erode (Webster 2011 in press).

Pollen data from lake cores in the Petén (e.g., Rosenmeier et al. 2002; Wahl et al. 2006;

Wright et al. 2009) have confirmed that high forest species prevailed until about 1000 BCE, when there was a noticeable shift to grasses and weeds. The need to collect pine trees for use in house construction and as fuel for cooking, heating, and the production of lime plaster and ceramics is likely to have contributed to the deforestation (Abrams and Rue 1988;

Dunning and Beach 2010). Most scholars attribute the change in vegetation to human forest clearing but the climatic drying trend that dates to the first millennium BCE may have contributed (Anselmetti et al. 2007; Brenner et al. 2002; Ford and Nigh 2009). Reforestation is believed to have begun at around 1000 CE in many locations (Rice 1996) but not before

European contact in others (Brenner et al. 2002). Climate may also have been a factor in forest recovery, with wetter conditions facilitating regrowth of arboreal taxa (Brenner et al.

2002; Ford and Nigh 2009).

Recent research indicates that Maya land use may have been more sustainable, at least in some regions. Deer bone samples from a number of sites in the Petexbatún region indicate

40 that the animals’ diet had remained stable from the Preclassic to Late Classic periods (Emery et al. 2000), suggesting that forest cover had not substantially changed. Bones of deer, peccaries and agoutis recovered from elsewhere in the Maya lowlands show that that the animals had fed primarily on forest plants between the Preclassic and Late Classic (Gerry and Krueger 1997; Wright 1997b). A sediment core from a pond near the urban center of

Copán indicated that forest pollen had actually increased between 400 and 700 CE (McNeil,

Burney, and Burney 2010).

The potential for agricultural productivity in the Maya lowlands depends primarily on soil type and drainage. The well-drained upland slopes are dominated by thin Mollisols, which are unusual in tropical environments (Fedick and Ford 1990). The perennial riverine wetlands also contain fertile Mollisols and lend themselves to raised- or ditched-field agriculture. The extensive slow-drained lowlands and the bajos are both composed largely of clay-like soil that becomes extremely hard when dry and sticky when wet, making those areas poor environments for agriculture. Isotopic analysis of 13C/12C ratios in soil organic matter provides a means of locating and quantifying areas of maize cultivation (Wright et al 2009).

The technique relies on the fact that maize and forest taxa incorporate atmospheric CO2 by different mechanisms. So-called C4 plants such as maize and other grasses discriminate less against the heavier isotope of carbon than do the C3 plants of the tropical forest. A relative increase in 13C is therefore a sign that the soil had once supported maize agriculture.

The choice of land for maize cultivation seems to have varied from one Maya settlement to another. At Piedras Negras in the northwest Petén, Fernandez et al. (2005) discovered isotopic signals for maize sandwiched between the native-plant signatures that predominated at the surface and in the deepest soils. The strongest signals for cultivation were near the

41 center of the settlement, suggesting that agriculture had begun there earlier than at the periphery, which was planted only later as the population grew. Researchers in the Tikal area

(Burnett et al. 2011) and near Motul de San José in northern Guatemala (Webb et al. 2007) found that maize planting was more common on the gentle foot- and toe-slopes farther away from the population center. Webb and her colleagues found no correlation at all between soil type and isotopic evidence of maize cultivation at Motul de San José (Webb et

al. 2007), and they discovered only a weak C4 signature in soils from the terraced slopes of

Caracol (Webb, Schwarcz, and Healy 2004).

The location of large settlements alongside bajos indicates to many scholars that they must have been important to the ancient Maya. At the site in the Petexbatún region, isotopic signals for maize were significantly greater in samples from bajos and rejolladas

(karst depressions) than in control samples from areas judged unsuitable for agriculture, such as steep hillsides and ledges (Johnson et al. 2007; Wright et al. 2009). The idea that the bajos had once been lakes was suggested by C. Wythe Cooke (1931) and was revived four decades later by Harrison (1977) and more recently by Dunning and his colleagues (Dunning et al.

2002, 2007). The authors argued that the lakes had become silted during the Late Preclassic period (400 BCE-150 CE) because of extensive deforestation. Other Mayanists (e.g., Beach et al. 2008) have proposed that the bajos may have supported intensive agriculture precisely because of soil erosion from the slopes, which deposited rich sediments at the bajo margins and made them suitable for cultivation. Research shows that the bajos at Calakmul, in the southwestern Yucatán, would have been too saline to be used for horticulture before the calcium-rich soils from the uplands had eroded into them (Gunn et al. 2002).

42 Hansen et al. (2002) have argued that the perennially wet marshlands known as civales, which are nearly always found today adjacent to or within bajos, were once productive environments for agriculture and wildlife. They discovered within several civales an A-horizon of mineral-rich soil about a meter beneath the accumulation of Maya clay. Pollen analysis showed that the horizon contained a higher proportion of grasses than the layer above it, which was dominated by forest taxa. Soil samples from garden terraces in the Nakbe complex revealed that the imported mud used to construct them matched the color and texture of the A-horizon in the civales four kilometers away, and that the mud contained pollen from marsh species. The authors suggested that the Maya had chosen to live along the bajos, which were then perennial wetlands, in order to take advantage of the nutrient-rich mud they contained.

Raised-field and canal systems, once believed to be common throughout the Maya wetlands (Adams 1993; Adams, Brown, and Culbert 1981; Adams et al. 1990; Turner 1978;

Turner and Harrison 1981), have been documented only in the perennial wetland areas of northern Belize and southern Quintana Roo, where the water table remains at or near the surface year-round (Fedick and Ford 1990; Pope and Dahlin 1989). Even there, raised field cultivation may have been less widespread than originally thought: some researchers believe that many of the suspected canals in northern Belize are actually natural formations (Pohl et al. 1996). Contrary to the claims that intensive wetland agriculture was a response to Classic- period population pressure (Turner and Harrison 1981), Pohl and her colleagues found that the canal systems had been constructed as early as 1000 BCE and were largely abandoned by the early Classic period. No evidence of wetland field systems has been found in the bajos of

43 the more densely settled Petén region (Dunning 1996; Pope and Dahlin 1989; Pope and

Dahlin 1993).

Agricultural terracing has been documented in only a few regions of the Maya lowlands.

At Caracol, stone terraces up to a kilometer in length cover nearly the entire landscape. The majority of the terraces, initially constructed in the Late Classic period after 550 CE and modified over the following 250 years, represented “a substantial ‘capital’ investment in terms of time, labor, and planning” (Chase and Chase 1998:66). Terraces in the Petexbatún region in Guatemala, on the other hand, covered only about a quarter of the hilly terrain and they were more modest in scale. Dunning and Beach (1994) identified several types of terraces at the Petexbatún settlement of Tamarindito. Dry-slope terraces had been constructed by digging behind rock outcrops and enabling the erosion to fill in the empty space, check dams or weirs served to diffuse sediments and runoff to create level surfaces, and foot-slope walls contained eroded soils at the base of hills. The terraces were dated to the Late Classic period between 550 and 830 CE and, like those at Caracol, appeared to have been built incrementally over time. In the Three Rivers region of northwestern Belize, Beach et al. (2002) described terraces similar to those in the Petexbatún. No terracing has been found in the central Petén region, an area believed to have supported some of the largest

Classic populations (Dunning and Beach 1994; Kunen 2001).

Many Mayanists believe that efforts to increase the amount of land under cultivation were supplemented by the use of various agricultural intensification techniques. In typical forest fallow agriculture, a field is cultivated for one or two years and then abandoned for

20-25 years to allow the soil to recover. With extensive fallow shortening, farmers may fallow their fields for as little as one or two years between plantings or eliminate fallow

44 periods entirely (Boserup 1965:25). Annual cropping with only a few months’ fallow each year and multi-cropping with two successive harvests each year are additional strategies that the Maya may have used to feed a growing population (Johnston 2003). At Tamarindito, changes in pollen levels of weedy taxa indicated that fallow time had decreased until about

100 CE and that by 250 CE, the landscape consisted of short-fallow fields interspersed with patches of managed forest (Dunning and Beach 2010). The Maya may also have practiced cultivation lengthening, a technique that makes use of intensive weeding and mulching to increase the number of years over which a particular tract of land can be farmed (Johnston

2003). Cultivation lengthening can increase productivity more than fallow shortening but it requires a significant investment of labor. The fallow shortening method is less labor intensive but it may not always allow the soil to recover sufficient nutrients to produce high agricultural yields.

SUMMARY

The Mesoamerican climate is affected by winds and currents in both the Atlantic and

Pacific oceans. Data indicate that rainfall in the Maya lowlands was highly variable. The relatively moist regional conditions that prevailed during the late Holocene gave way to a drier climate starting at about 1000 BCE. Episodes of drought became increasing acute and frequent over the next 2000 years. Particularly severe multi-year droughts occurred during the early sixth century and the mid-seventh century. A prolonged dry period from about 810 to 938 CE coincided with the Maya “collapse.”

Evidence suggests that the Maya preferred to cultivate maize in flat areas with well- drained soils and only later, as the population grew, did they expand to the slopes, where the thin soil was more easily eroded. As forests were cleared for agriculture, increased runoff

45 resulted in thick deposits of clay in nearby lakes. The bajos, which are considered marginal areas for cultivation today, may once have supported intensive agriculture but they became silted in the Preclassic period, because of erosion, climate change, or both.

Raised field cultivation allowed the Maya to exploit the perennial wetlands during the

Preclassic period but those areas were later abandoned as the sea level rose. Late-Classic- period agricultural terracing has been documented in four regions of the Maya lowlands but is absent in other areas that have similar slopes. Hydraulic engineering projects, also undertaken during the Late Classic, may have enabled the ancient Maya to store rainwater for the dry winter months but those measures were probably insufficient to enable the population to endure a severe or protracted drought.

46 CHAPTER 4. MAYA POPULATION

Population data are important to the assessment of the bet-hedging model for several reasons. First, the model predicts that in uncertain environments reduced fecundity confers a fitness benefit. The lower birthrate would be reflected in proportionally fewer infants and children and a larger percentage of mature adults in burial assemblages. Second, settlement patterns can reveal how mobile the ancient Maya were. According to the model, the ability to buffer against a poor harvest by migrating to a more productive area would diminish—but not eliminate—the selective advantage of bet-hedging behavior. Finally, data about the Maya diet and the health of the population provide an indication of the extent to which resources may have been stretched as the population grew.

POPULATION SIZE AND DENSITY

Archaeologists have used two methods to estimate the population density of ancient

Maya settlements. The first estimates the maximum number of people that the environment can support. Early assessments of the carrying capacity of the Maya lowlands, which were based on the long-fallow swidden agriculture that is practiced there today, put maximum potential population densities at fewer than 80 persons per square kilometer (Brainerd 1956;

Morley 1956:47; Cowgill 1961). Short-fallow cultivation methods could probably have increased the carrying capacity to about 150-200/km2 (Webster 2002:264).

The second method of estimating population size makes use of settlement survey data.

Maya settlement studies began in the 1930s and became increasingly popular during the second half of the twentieth century. Researchers have distinguished three types of Maya housing units: single structures; informal groups; and courtyard groups (Marcus 1983).

Courtyard groups, also known as patio groups or plazuelas, consist of clusters of structures 47 that served as residences, kitchens, and storehouses (Willey 1980). Patio groups predominated at Tikal and other settlements in the southern lowlands (Haviland 1972;

Marcus 1983) but they were extremely rare at other sites such as Caracol (Chase and Chase

1998). Plazuelas themselves were generally arranged in groups of five to twelve, the largest of which are thought to have served as shrines or administrative structures (Willey 1980). While population reconstructions based on settlement studies often provide a relatively standard means of comparing sites (Chase 1997), they are subject to errors in sampling, misidentification of residences, erroneous dating, the potential for temporary disuse or abandonment, inaccurate family size figures, and the possibility of “invisible” structures detectable only by excavation and “hidden” structures overlooked in mapping (Rice and

Culbert 1990).

To estimate population size using survey data, archeologists count the number of house mounds in a sample area. Adjustments are then applied to try to correct for some of the unknown variables. Archaeologists typically add 10-35% to the raw household counts to adjust for the possibility of unmapped structures. They subtract 5-30% to correct for misidentification of platforms as residences (Rice and Culbert 1990). To arrive at a figure for population density, the adjusted number of structures is multiplied by a constant that is believed to represent the average number of residents per house. For the Maya that number, based on ethnographic data, generally varies between 4.0 and 5.6. Site-wide population estimates then factor in the total area in which “urban” and “rural” house mounds are found.

Even after the corrections, some scholars believe that the settlement survey approach may greatly overestimate population densities. Studies of several lowland settlements have

48 shown that at least 40-50% of structures surveyed did not serve purely residential purposes

(Santley 1990). The largest potential source of error comes from estimates of simultaneously occupied structures. In nearly all the population studies, the assessment of duration of occupation of a residence relies solely on ceramic assemblages (Haviland 2003; Rice and

Culbert 1990). Ceramic phases have been established at many lowland settlements, but they generally do not have fine chronological resolution. At Tikal, for example, ceramic complexes range in duration from 100 to 350 years (Culbert et al. 1990). The presence of pottery sherds from a particular ceramic phase is taken as an indication that the residence was occupied for all or part of the time that the style was in use. Some Mayanists favor the

“continuous occupation model,” which assumes that once inhabited, a structure would continue to be used without interruption until a period of widespread population decline or abandonment (Culbert et al. 1990:109). Haviland (1970, 2003) has argued that at Tikal, evidence of frequent alteration and continuous midden deposits, the absence of deterioration of walls and floors due to exposure to the outdoors, and the rarity of burial disturbance all indicate that occupation was probably continuous. At the other end of the spectrum, advocates of the “cyclical abandonment model” assume that residences had finite durations of use (Culbert et al. 1990:109). Their population estimates are often based on a presumed

100- or 150-year-long occupation of each structure before it is abandoned. Determining the duration of occupancy is critical in estimating population size for a given period. Santley

(1990:333-334) explains:

The grossly inflationary effects of entrenchment and reoccupation on Maya house-mound counts should be obvious. If habitation structures went through an occupation/abandonment cycle but were consistently reused at the end of each cycle, house-mound counts would have to be reduced by a factor of 50% to estimate the number of buildings simultaneously occupied by families. Total counts might have to be

49 reduced by a factor of 75 to 90% if structure use-life was short (e.g., 25 years) but the reuse cycle was comparatively long (e.g., 100-125 years). Entrenchment, with each coresidential group maintaining one or more field houses, would require a further 50-75% reduction to estimate the number of structures inhabited by family groups on a contempo-raneous basis. Finer periodizations will not allow resolution of these problems, as most structure-occupation/abandonment cycles are probably well within the limits of the finest chronologies. Neither will the blanket application of a correction figure help us much, for the mobility requirements of a population are likely to change from one time period to the next if demographic growth occurs and subsistence strategies change.

Gaps in ceramic phases have been documented, but temporary short-term abandonment of a house would be difficult to detect archaeologically.

Late Classic population estimates for selected lowland Maya centers are presented in

Table 4. The estimates range from an urban density of about 900 people to more than 7700

Table 4. Late Classic Maya population estimates in selected lowland areas. AREA DENSITY AREA POPULATION SOURCE (KM2) (PEOPLE/KM2) Tikal 123 325-365 40,000-45,000 Haviland 1970, 1972 Central zone 63 600-700 39,000 Haviland 1970 Peripheral zone 60 100 6000 Haviland 1970 Tikal 120 516 62,000 Culbert et al. 1990 Urban core 9 922 8300 Culbert et al. 1990 Rural area 194 153 53,700 Culbert et al. 1990 Copan 20,000-25,000 Webster and Freter 1990 Urban core 1.19 4871-7743 5797-9464 Webster and Freter 1990 Caracol 177 847 150,000 Chase and Chase 1998 Sacnab- 29 212 6253 Rice and Rice 1990 Macanche-Salpeten 29 250 7262 Rice and Rice 1990 Quexil-Petenxil 23 164 3836 Rice and Rice 1990 Tayasal 90 250-341 21,951-33,272 Chase 1990 Tayasal spine 8 858-1300 6861-10,400 Chase 1990 9 761 6850 Healy et al. 2007 Pacbitun core 1 1218 1218 Healy et al. 2007 people per km2 for some of the largest Maya settlements and from 325 to 847 people/km2 when rural areas are included. The density figures in the table incorporate a variety of

50 correction factors but they all reflect a simple ratio of people to land, without any consideration for uninhabitable areas such as bajos. In areas where bajos make up a sizeable proportion of the terrain, as in the central lowlands, calculations of density per habitable square kilometer would be substantially higher.

Population growth and decline are believed to have varied widely across the Maya lowlands. Changes in population sizes for selected lowland settlement areas over a two- millennium time span are shown in Figures 7 and 8. The figures represent percentages of the total population of each site at its maximum size, regardless of when the maximum was reached. Continuous-model population percentages, plotted in Figure 7, indicate that some populations reached their maximum size in the Classic period, while in other parts of the lowlands population size had a bimodal distribution. Figure 8 shows the population curves for the same five

Figure 7. Population growth (continuous occupation model). The data are from Rice and Culbert (1990). Raw figures appear in Appendix C. settlements with the figures adjusted for a 150-year cyclical occupation model. With the correction, populations in all five settlement areas reach their maximum in the Late and 51 Figure 8. Population growth (150-year platform use model). The data are from Rice and Culbert (1990). Raw figures appear in Appendix C.

Terminal Classic periods. One Mayanist (Santley 1990) has noted that large landlocked centers such as Tikal and Calakmul seem to have experienced exponential population growth and decline, while coastal and riverine areas where no monumental architecture has been documented, including and the Belize River Valley, showed a “sawtooth” logistical pattern of increase, loss, and recovery. Those trends, if they are correct, are exactly the opposite of what the waste hypothesis would predict.

Perhaps the most extensive survey of Maya settlement is at Copán, where Webster and his colleagues (Webster et al. 2000; Webster 2007, 2008; Webster and Freter 1990) have worked for several decades. Large quantities of obsidian at Copán allowed for more precise dating than the ceramic sequences used elsewhere in the lowlands. Each dwelling surveyed was classified as elite or commoner according to its size and elaboration. The number of rooms, rather than structures, provided the basis for calculating population density, with an adjustment made to give more space to individuals in elite households. Using a procedure that the authors designed specifically to produce maximum population numbers, they

52 assumed that each room housed five people during the presumed growth period from 400 to

749 CE; four people between the years 750 and 899 CE, when the population was thought to be stable; and 3.5 people thereafter, when the population was considered to be in decline.

The reconstruction showed that the population had increased from several thousand people in 400 CE to a peak of about 27,700 in 750 CE (Webster et al. 2000). Population size remained stable until 900 CE, with 75-80% of the total concentrated in the Copán pocket

(the 24-km2 area surrounding the urban core). As many as 9,000 people lived within the urban core in an area of about one square kilometer. By 1200 CE only about 1,000 people remained in the entire settlement. During the decline, the population became less centralized, with only half the inhabitants living in the Copán pocket.

A simulation of the carrying capacity of Copán (Wingard 1992) indicated that long-fallow maize cultivation of the alluvial foothills could have supported a population of about 5,000.

Annual cropping would have fed an additional 1,400 people. A population continuing to grow would have had to rely on farming the more marginal soil of the hillsides. Extensive cultivation and double-cropping of the alluvial plain would both have been necessary to support a population of 20,000, a strategy that could not have been sustained for an extended period of time.

The disparity between the size of the population that the environment could support and the estimates of population based on house structures has puzzled Mayanists for several decades. Some scholars have attempted to resolve the discrepancy by positing that greater agricultural yields would have been possible with strategies such as terracing, irrigation, and cultivation lengthening. Others have suggested that the Classic Maya relied for subsistence on root and tree crops when maize was unavailable (e.g. Bronson 1966; Ford and Nigh 2009;

53 Nations and Nigh 1980; Puleston 1982; Wilken 1971). Still other Mayanists have argued that the house-count population figures are simply too high.

One reason the population might have been overestimated is that people were counted more than once. An increase over time in the number of structures in a settlement may reflect population movement as well as local population growth (Tourtellot 1993). During the early Classic period, population losses in the Macanche-Salpeten and Quexil-Pintenxil zones of the Petén were contemporaneous with population increases in nearby Yaxha and

Tikal, suggesting that the change was due to local migration (Rice and Rice 1990). Noting

16th-century reports of the Maya practice of abandoning their huts for periods of time after burial of a family member, Thompson (1971) speculated that the custom may have had ancient origins, providing an emic rationale for the cyclical occupation model. Intermittent occupancy of rural dwellings may also have inflated population estimates. Less domestic refuse is found near rural house-mounds in the Copán Valley than near those in the urban area, suggesting that dwellings outside the densely populated core may have been occupied seasonally by farmers whose families remained in the urban center year-round (Santley 1990).

Webster and his colleagues (2000:187) speculated that people may have lived for part of the year in distant parts of the valley and then returned to the center with their harvests. In the absence of more information about migration patterns and mobility strategies, the number of house mounds may be an unreliable indicator of natural population growth or decline.

BIOARCHAEOLOGICAL RESEARCH

Over the past two decades, advances in laboratory techniques and analytical methods have enabled physical anthropologists to refine their analyses of bones and teeth recovered from archaeological contexts. Their investigations reveal clues about migration patterns and

54 fertility rates, variations in diet, and incidence of warfare and disease. A growing body of literature is devoted to osteological and dental studies of ancient Maya burial populations.

Some of the recent findings are reviewed here.

Migration

Strontium isotopic ratios in human bones and teeth can be used to discern migration patterns because the ratios reflect the sources of food and water in the diet, which in turn depend on the geology of the local bedrock. In dental enamel the ratio of strontium isotopes is fixed in early childhood but in bone the ratio changes over a person’s lifetime. Isotopic differences between the bones and teeth of a skeleton are indicative of changes in a person’s residence. Strontium isotope ratios in tooth enamel can also be compared to those in the local soil and in archaeological faunal remains to determine whether a person is likely to have migrated between childhood and death.

Although the preservation of bones is poor in many Maya burial assemblages, the geographical variability of the Maya lowlands makes strontium isotope analysis of human remains an effective technique for identifying migrants. Based on strontium isotopes in the local water, bedrock, soils, and plants, Hodell et al. (2004) identified five distinct Maya subregions—the northern lowlands, southern lowlands, metamorphic province, Belize

Mountains, and volcanic highlands/Pacific coast. Wright (2005) examined tooth enamel of

83 individuals from a variety of contexts in Early and Late Classic Tikal burials. Using the isotopic averages for the five regions that Hodell and his colleagues had established, Wright determined that eight skeletons belonged to people who had clearly migrated from a different region. Another 4-13% of the skeletons probably belonged to immigrants from elsewhere within the same region, suggesting that migration had been a significant factor in

55 the growth of Tikal’s population. The author cautioned, however, that because some of the skeletons had been recovered from ritual contexts, the proportion may not be representative of the entire population.

Freiwald (2011) analyzed 87Sr/86Sr isotope ratios in the teeth and bones of 178 individuals recovered from 19 Late and Terminal Classic sites in the Belize River Valley, an area with large geological variation within relatively short distances. She found that 23% of the individuals had relocated at least once in their lives. Price et al. (2008) examined human and faunal remains from burials in the distant settlements of Teotihuacan, Copán, Tikal,

Palenque, and Campeche. The results indicated that variation in strontium isotopic signatures within a region was considerably less than the variation among regions, indicating that migration was largely an intraregional phenomenon.

Research on morphological variation in dental remains has produced mixed results. One study (Scherer 2007) examined metric variation in the teeth of 321 skeletons from 12

Classic-period archaeological sites located in modern Mexico, Guatemala, Belize, and

Honduras. Statistical analyses revealed no correlation between geographic and biological distance in his sample, suggesting that there was extensive gene flow throughout the lowlands during the Classic period. Wrobel (2004), on the other hand, compared dental remains from burials in three northern-Belize sites to those in samples from the Pasión region, and found significant differences between the two locations.

Demographics

Conclusions about past population demographics such as age and sex distribution are necessarily tenuous. Sample sizes are often small. Methods for determination of age and sex are controversial. Infants may be underrepresented because of poor preservation conditions

56 (Wood et al. 1992; Wright and Yoder 2003). Inferring the health of a living population from skeletal data is even more problematic. As Wood and his colleagues (Wood et al. 1992) have shown, skeletal series are inherently unrepresentative of the living population because they include only those individuals who succumbed to some stressor. Contemporaries who survived may have experienced the same or greater stress but were less susceptible to it.

Because of the “selective mortality problem” (Wood et al. 1992:344), levels of disease in a population will be overestimated if they are based solely on skeletal lesions. Frequency of disease may also be underestimated because only a small proportion of individuals who experience chronic disease will develop the tell-tale skeletal lesions. There is no reason to expect that the two bias errors will balance one another (Wood et al. 1992).

Despite those concerns, age-at-death data and the number of stress-related lesions found in Preclassic and Classic Maya skeletal assemblages can provide clues about changes in age distributions and health conditions of Maya populations over time. In an excavation of 166 burials in , Belize, spanning the entire Preclassic period from about 1200 BCE to 100

CE, Saul and Saul (1991, 1997) found that the population was predominantly middle adult

(age 35-54) or younger, with two definite and 28 possible older adults. The ratio of adults to subadults was 130:36. At Caracol, Chase (1997) found that the skeletal population during the

Classic period ranged from infants to adults over 50 years old, with the majority between 25 and 35 years of age. Infants made up 14.79% of the burial population, while 11.24% were individuals over 35 years of age. The picture was different at Tayasal in the Late Classic period, where only 5.36% of the sample was composed of infant skeletons, and 23.21% was over 35 years old (Chase 1997). Of the 30 skeletons recovered from a Terminal Classic-

57 period burial in Colha, Belize, 20 were adults, three were infants under a year old, and the remaining seven were between the ages of 1.5 and 7 years at death (Massey and Steele 1997).

Storey (2006) compared different methods of age-at-death determination for a sample of

400 individual skeletons from Late Classic-period (650-1000 CE) Copán. Although the methods yielded somewhat different distributions, they all indicated an aging adult population. About two-thirds of the skeletons came from elite residences, which Storey admits may have skewed the results. Whittington (1989, 1991) avoided that confounding factor by examining burials in and near some of the least elaborate houses in Copán, which were likely to have belonged to low-status individuals. In his sample of 160 skeletons, there was a considerably higher proportion of older individuals in the Late Classic period (700-

1200) compared to the Middle Classic population (400-700 CE). Because changes in age-at- death distributions are known to reflect birth rates more than mortality rates, Whittington concluded that the fertility rate in Copán had declined during the Late Classic period.

Diet

Isotopic studies of bone collagen have been performed at some 26 lowland Maya settlements in an effort to reconstruct ancient Maya diets (Wright 2004). The ratio of 13C/12C in human and animal bone provides a proxy measure for maize consumption because maize contains a higher percentage of the heavier isotope than the other cultivated and wild plants in the lowlands. The 15N/14N ratio indicates the proportion of dietary protein that comes from animal and plant sources because 15N is enriched in mammalian digestive systems

(Wright 1997b). Some Mayanists (e.g., Lentz 1991; Santley 1990; Santley, Killion, and Lycett

1986) have argued that rapid population growth in the Late Classic period would have put a strain on resources, resulting in more restrictive diets and increasing susceptibility to

58 infection. Analyses of human and animal skeletal remains, however, do not support the idea that the Maya suffered dietary insufficiency or deteriorating health during the Classic period.

The Maya everywhere depended heavily on maize, but their diets varied with location, gender, and social status. Copán had the lowest consumption of meat of all lowland Maya populations during the Classic period (Gerry and Krueger 1997; Whittington 1989).

Inhabitants of Lamanai, Pacbitun, and the Belize Valley consumed a wider range of food resources, presumably because of their proximity to the Caribbean coast. In the Petén region, the Maya diet contained about the same proportion of maize as at Copán but included significantly more animal protein (Gerry and Krueger 1997). At Pacbitun, maize represented more than 70% of elite diets and about 50% of commoner diets. Meat consumption, however, did not appear to vary with status (White, Healy, and Schwarcz

1993).

Changes in the Maya diet over time are evident in some settlements but not in others. At

Lamanai maize constituted about half of all dietary carbohydrates in elite diets between the

Preclassic and Early Classic periods, declined to about 37% in the Terminal Classic, and then rose to 70% in Postclassic times. The nitrogen isotope ratio, on the other hand, remained stable from Preclassic to historic times, suggesting that there was no change in the amount of meat available to the Maya (White and Schwarcz 1989). In contrast, commoners at Copán had a diet that was higher in maize content during the Classic period than in the Postclassic.

Men and women consumed the same amount of animal protein but men ate proportionally more maize (Whittington and Reed 1997). In the Pasión region reliance on maize did not change between the Preclassic and Terminal Classic periods, although there too, men consumed proportionally more maize than women. Meat consumption continued to

59 contribute a substantial amount of dietary protein even in the Late-Classic period (Wright

1997b). In the nearby Petexbatún region, a study of faunal remains showed that nutritionally high-ranked white-tailed deer remained in considerable abundance even in the Late Classic period (Emery 2008).

Health

Although the physical data indicate that the ancient Maya suffered from diet-related health problems, their health does not appear to have worsened between the Preclassic and

Late Classic periods. Wright (1997a, 1977c) examined teeth and bones recovered from 160 adult skeletons from burials in six settlements of the Pasión region. Indications of stress known as hypoplasias were found on the teeth of 59% of the individuals. The frequency of stress, however, was stable from 600 BCE to 950 CE, indicating that population growth over the course of 1500 years had had no effect on nutritional health. Whittington (1989) found that enamel hypoplasias were common in the teeth of low-status subadults at Copán, particularly during the Late Classic period. Because the peak age of hypoplasias is thought to indicate weaning age (Wright 1997c), Whittington concluded that children were not weaned until they were about four years old. He noted that a late weaning age has the effect of reducing female fertility and increasing inter-birth intervals.

One consequence of a maize-dependent diet is a high incidence of iron deficiency and childhood anemia, which can cause of a type of cranial lesion called porotic hyperostosis, especially in combination with weanling diarrhea, parasites, and infectious diseases (Wright and Chew 1998). Of the 160 adults in Wright’s sample (Wright 1997a, 1977c), 65% showed evidence of porotic hyperostosis but the percentage of cases did not vary over time. Signs of infectious disease likewise showed no increase between the Preclassic and Late Classic

60 periods. Wright and Chew (1998) found that porotic lesions were much less abundant in modern adult Maya remains, which suggests that the Classic Maya were more likely to survive malnutrition into adulthood. That inference is supported by data that indicate that the Classic Maya were taller than their modern descendents (Márquez and del Ángel 1997;

Wright and Chew 1998).

SUMMARY

There is a striking disparity between population estimates based on carrying capacity of the lowland Maya environment and those based on house mound counts. It seems likely that the exponential growth rates indicated at some large settlements reflect immigration as well as natural increase. On a regional scale, some settlements saw population losses at the same time that others experienced gains. At an individual level, isotopic strontium signatures in skeletal remains have shown that migration in some areas was as high as 23%. An influx of immigrants would explain how the fecundity rate could have been declining in Late-Classic

Copán at the same time that population growth was assumed to be at its highest rate.

Substantial evidence indicates that the Maya diet was heavily dependent on maize. At some settlements elites consumed a larger proportion of maize than commoners and men often ate more maize than women, perhaps because they spent more time in the fields. The availability of animal protein seems to have varied more with location than time period, gender, or social status. Faunal analysis showed that deer meat remained available in many regions throughout the Classic period. There are no signs of deterioration in health between the Preclassic and Classic periods and therefore no evidence of stress due to population pressure or food shortages.

61 Maya burial assemblages are small and age-at-death data are an unreliable indicator of living population demographics. Nevertheless, the evidence suggests that the population had aged between the Preclassic and Late Classic periods. Maya diet and health profiles remained relatively constant throughout the period, implying that the changes in age distribution may be attributed to reduced fecundity, decreased infant mortality, or a combination of the two.

62 CHAPTER 5. DISCUSSION AND CONCLUSIONS

Ancient farmers everywhere used four kinds of strategies to hedge against risk: crop diversification, physical storage, exchange, and mobility (Halstead & O’Shea 1989). In the

Mesoamerican lowlands, however, most of those strategies could not be implemented. The

Maya had little opportunity for dietary diversity, compared to other pre-modern cultures.

Maize represented up to 70% of the Maya diet, with the remainder accounted for largely by beans, squash, and tree fruits such as avocado and nance (Lentz 1991). In inland areas, faunal sources of food were limited to deer, dogs, wild boar, wild birds, peccaries, and agoutis (Coe 1999a:58; Emery 2008; Lentz 1991).

Long-term food storage was not feasible because agricultural products could be preserved for only a year or so in the subtropical climate (Webster n.d.). Opportunities for trade were probably also limited. While Andrews (1984) has argued that perishable goods including cotton, cacao, and animal and plant foodstuffs, traveled across long-distance trade networks in the Classic period, other researchers (Tourtellot and Sabloff 1972; Marcus 1983;

Webster 2007, n.d.) believe that subsistence goods and utilitarian items were traded only locally. In any case, transporting agricultural goods on foot over long distances would have been impractical because the deliverers would likely have consumed their loads before reaching their destination.

The fourth buffering mechanism is mobility. Migration probably accounted for at least some of the population shifts during the Classic period, as well as at the end of the Preclassic period, when the largest centers of the El Mirador basin were apparently abandoned.

Bioarchaeological data support the idea that intraregional migration was quite common.

Analysis of strontium isotopes in skeletal and dental remains indicates that a significant

63 percentage of the population of the Belize River Valley had relocated at least once. To the extent that crop yields varied spatially, migration would have been an effective strategy for coping with local food shortages.

Mobility and frequent migration may also account for the fact that Maya populations have been estimated at well beyond the carrying capacity of the environment. Assessments of population size based on house mound counts are fraught with the potential for error. In particular, if houses had been abandoned for a significant length of time, as many Mayanists have argued, or if farmers maintained dual residences, as they do today (Cowgill 1961), population estimates could be off by more than 50%. Skeletal data from Copán suggest a lower fecundity rate during the Late Classic period, a finding at odds with the settlement surveys that imply that the population was then growing at its fastest rate, unless the population increase was due to the influx of immigrants. A change over time in family size, if it did occur, would be impossible to detect using methods that assume a constant number of inhabitants per room or household.

The bet-hedging model for cultural elaboration proposes that people in ancient societies who had to contend with unpredictably variable environmental conditions may have benefited from a fifth strategy as a hedge against crop failure. That strategy was to limit population growth. According to the model, any activity that diverts energy from reproduction will have a selective advantage in uncertain environments because reduced fecundity increases reproductive fitness. The proximate causes of reduced fecundity will obviously vary from one society to another. Customs such as delayed marriage, postpartum sexual abstinence, infanticide, and late weaning are well-attested in the anthropological literature (e.g., Johnson 1990; Wood 1990), and each of them would have the effect of

64 curtailing population growth, regardless of how or why the practice was adopted. In fact, any cultural behavior that results in reduced fecundity will serve as a hedge against uncertainty, whether or not it was introduced or performed for that purpose.

Monumental architecture is the most visible sign of such “wasteful” behavior. The fact that monumental constructions appear in the archaeological record in some of the most marginal agricultural areas suggests that the evolutionary payoff was significant. Investments such as monument building would be a particularly effective strategy among societies with few other risk-management options. In environments like the Maya lowlands that are both temporally and spatially variable, the ability to migrate to areas with more favorable conditions may have lessened the selective advantage of investments in wasteful activity, but would not be expected to have eliminated it entirely (Madsen et al. 1999).

Much of the environmental and archaeological data collected over decades of research on the Preclassic and Classic Maya is consistent with the expectations of a bet-hedging model. Like other semi-tropical humid forests, the Maya lowlands generally represented a poor environment for agriculture. Agricultural productivity was hindered by the fact that the

Maya had no large domestic animals. Plowing and planting had to be done by hand, using implements made of wood, stone, and bone, because the Maya had no metal tools. While there is evidence that the lowland Maya modified their landscape for cultivation and employed intensive agricultural techniques, the timing and scope of those activities remain a subject of debate among scholars. In the perennial wetland areas, raised- and ditched-field agriculture may have allowed the Maya to cultivate maize during the dry season but the platforms and canals that researchers have discovered had been abandoned by Classic times, either because of increased runoff or a rise in sea level. Terraces would have hindered soil

65 erosion and nutrient depletion but they have been found in only a few locations across the

Maya lowlands. Even if the bajos, which covered more than 40% of the total land area, had once been productive agricultural land, the evidence indicates that they became silted due to erosion during the Late Preclassic period, centuries before the so-called florescence of Maya civilization. The channels, reservoirs, dams, weirs, and other hydraulic constructions that the

Maya built may have provided drinking and irrigation water during the dry season but those structures have been documented in only a few regions of the lowlands. Aggressive mulching, weeding, and fertilizing could have substantially increased maize yields but those activities are extremely labor intensive (Johnston 2003; Willey 1980) and difficult or impossible to detect in the archaeological record. The array of strategies the Maya employed to preserve and control water resources and increase crop yields may not have been sufficient to feed a growing population in a region where rainfall varied unpredictably.

The Mesoamerican climate is affected by a variety of large-scale atmospheric and oceanic disturbances including shifts in the intertropical convergence zone and movements of the

North Atlantic High. Smaller-scale perturbations in local climate conditions are the result of

Central America’s unique location between two continents. In modern times, variation in inter-annual rainfall is as high as 30-40% (Dunning and Beach 2010). Paleoclimatic data indicate that the Maya lowlands experienced significant temporal variability including repeated, severe periods of drought over the two-thousand-year period between about 1000

BCE and 1000 CE. A number of prolonged droughts occurred between 250 BCE and 1000

CE, the period of the Preclassic and Classic Maya occupation.

Construction of monumental architecture in the Maya lowlands began shortly after the onset of drier and more variable climate conditions, as it had in Peru (Kornbacher 1999),

66 Egypt (Sterling 1999), and the Mississippi Valley (Hamilton 1999). Some of the largest was located in the relatively marginal southern and central lowlands, just as

Ireland’s megalithic monuments were more commonly found in regions where agriculture was the least productive (Aranyosi 1999). The Maya areas lacking water resources were the last to cease building monuments. McAnany and Gallareta Negrón (2010:155) noted:

[T]he large political capitals on the edges of the Maya world that sat astride a permanent water source—Copán, Quirigua, Piedras Negras, and — were some of the earliest to cease constructing new buildings and carving sculpture with hieroglyphs and long-counts dates … In contrast, dynastic seats such as Tikal, Calakmul, and Caracol that are located in the interior of the Lowlands—where there are no rivers and water is seasonally in short supply—survived longer.

Except for a mid-Classic hiatus in construction in some central lowland settlements, both the pace and scale of monument building increased during the Classic period. Construction activities resumed and even intensified after each of the most significant periods of drought, indicating that repeated dry periods did not deter Maya building and instead, may actually have encouraged it, as the bet-hedging model predicts.

If labor costs are measured by the per capita investment in monument construction (e.g.,

Abrams 1989; Drennan, Peterson, and Fox 2010; Webster and Kirker 1995), the Maya were perhaps not as “wasteful” as many other ancient societies; research suggests that the amount of effort needed to construct the Maya monuments may have been substantially less than originally thought. Dividing the total volume of civic construction in three Maya settlements by the number of mapped house mounds, De Montmollin (1995:211) calculated that the per-family workload appeared to be quite light, although he acknowledged that his figures did not take into account the cost of continuing upkeep. Other estimates of labor costs have measured the time required to build an existing structure using the tools and techniques

67 available to the Classic Maya, a methodology known as architectural energetics (Abrams

1989, 1994). Abrams (1987) determined that a maximum of 30,500 person-days would have been needed to procure and transport the material for the Temple of Meditation (Structure

10L-22) at Copán and to build and decorate the structure. Assuming that all of the work took place during the four-month dry season and within a single year, Abrams calculated that the project would have required a labor force of just 371 construction workers, each conscripted for 60 days, in addition to about 40 specialized plasterers and sculptors. Similar calculations indicate that Temple 26 at Copán would have taken 124,000 person-days to construct and that Temple 1 at Tikal could have been built in 90,000 person-days (Webster and Kirker 1995). If projects like those were spaced over a ruler’s lifetime, they would have involved only a small proportion of the workforce during a single year (Webster 1985).

Although the level of investment in cultural elaboration may vary widely, any activity that does divert energy from reproduction would have a selective advantage in an unpredictably variable environment. The model does not—and cannot—specify a requisite quantity of energy investment because that amount will depend on the unique combination of environmental and biological factors at play at various points in an individual’s lifetime. The diversion of resources from reproduction should be reflected in a lower birthrate and reduced juvenile mortality. Indeed, studies of Maya skeletal assemblages in Copán have shown that the Late-Classic population was aging and that fecundity had declined between the Preclassic and Classic periods (Story 2006; Whittington 1989, 1991).

More research is needed to refine the bet-hedging model for cultural elaboration.

Because bet-hedging theory is sufficient to explain reduced fecundity in temporally variable environments without the requirement that energy be diverted to “wasteful” activity (Nolan

68 and Howard 2010), archaeologists have begun to explore the way in which cultural elaboration and reproductive effort may become linked. Attempts to combine the perspectives of behavioral ecology and evolutionary archaeology show promise in clarifying how the two traits become associated and transmitted to others “as a package” (Madsen et al. 1999:267). While evolutionary archaeology and human behavioral ecology and have been considered distinct and even competing conceptual approaches, they actually complement each other in many respects (Nolan and Howard 2010; Shennan 2008). An investment in costly signaling, for example, can be understood as a strategy that maximizes benefit over expenditure or as a diversion of energy to wasteful behavior.

Nolan and Howard (2010) proposed a model that combines concepts from the two evolutionary approaches to archaeology in order to explain how cultural elaboration and bet- hedging behavior may have become linked during the Middle Woodland period. The model is based on the evolution of a symbiotic relationship between humans and the crops they exploit (Rindos 1980). Research indicates that previously farmed fields in the region were more productive than densely forested fields because seeds and greens could reestablish themselves more quickly in open areas. The authors suggested that any activity that caused those fields to be disturbed would retard reforestation and make food sources temporarily more abundant. Visiting the graves of ancestors or constructing mounds and other earthworks may have provided a reason for continued disturbance, but regardless of the proximal cause that drove people to return repeatedly to the same fields, those who participated in the practice would have received a fitness benefit.

Hunt and Lipo (2011:131-146) recently incorporated the concepts of costly signaling and bet hedging to explain cultural elaboration on Rapa Nui. They argued that the moai served as

69 signals of their builders’ ability to prevail in a challenge to their strength or unity. That costly advertising had the benefit of deterring conflict on the small island and also imparted advantages to both senders and recipients of the signal: signalers increased their attractiveness to potential mates or allies, while receivers were better able to “make informed decisions about mating, cooperation, competition, and so on” (Hunt and Lipo 2011:132).

The unintended consequence of the investment of labor in carving the statues and transporting them across the island was to divert energy from reproduction. In the long term, the behavior persisted because a smaller overall population was able to survive episodic fluctuations in crop yields. Another indication of bet hedging on Rapa Nui was the strongly biased ratio of men and women, evident in skeletal studies as well as in reports by early European visitors to the island. Regardless of the mechanism by which the sex bias was achieved, a disproportionally small population of women in such an isolated community would have effectively reduced the birthrate (Hunt and Lipo 2011:141-142).

Archaeological, physical, anthropological, and environmental data from the Maya lowlands support the expectations of the bet-hedging model, but additional studies will be needed to determine more conclusively the degree to which the theory helps explain the development, distribution, and disappearance of Maya monumental architecture. Most of the climatic reconstructions for the central and southern Maya lowlands have relied on analyses of sediment cores collected from lakes in the Yucatán. While that strategy has the advantage of reducing the confounding effects of human activity, it also precludes the detection of spatial variability. Finer-resolution dating of stalagmites from a variety of lowland locations will facilitate more reliable reconstructions of local paleoclimatic conditions. Skeletal samples in the semitropical Mesoamerican climate tend to be poorly preserved, and assemblages are

70 generally small and scattered because the Maya buried their dead under and beside their residences. Signs of an aging population and lower juvenile mortality suggest that the fecundity rate declined in the Classic period but larger sample sizes are needed to confirm those findings.

Inconsistent with the expectations of the bet-hedging model are population estimates that suggest that some settlements with substantial investments in monumental architecture grew at an exponential rate, while those lacking monuments grew more slowly. At least one

Mayanist (Webster 2009, 2011; n.d.) has challenged the high population estimates, claiming that some of the assumptions made in the calculations are probably unwarranted. If the estimates are accurate, however, it means that the investment in monumental architecture—a clear indication that energy was diverted from reproduction—was insufficient to constrain population growth in some areas during the Classic Maya period. Additional demographic and bioarchaeological research will be critical to a better understanding of Maya population history.

Many of the data deficiencies are already being addressed with the help of new technologies and methodologies. Remote sensing is being used to locate and map lowland

Maya settlements and to discern landscape use more quickly and inexpensively than ground surveys can, especially in heavily forested terrain (Chase et al. 2011; Garrison et al. 2011).

Those data will be useful in shifting from site-specific studies to research more focused on region-wide patterns. The use of geographic information systems in spatial autocorrelation research is proving helpful in recognizing Maya settlement patterns in ways that were impossible several decades ago (Kvamme 1990; Premo 2004; Williams 1993). Studies that employ powerful statistical techniques and population genetics modeling are enabling

71 researchers to make more reliable inferences about once-living populations from skeletal and dental remains (Wright and Yoder 2003).

Empirical evidence from around the globe supports the idea that cultural change, like biological evolution, is best understood as a process of descent with modification. The elements of Darwinian evolution—variation, transmission, and differential reproduction— are just as relevant in cultural contexts as they are in biological ones. In the evolution of species and cultural phenomena, the persistence and diversity of traits and behaviors can be explained by the processes of drift and selection. Although Darwinian theory by itself cannot provide a complete explanation for cultural or biological phenomena, it offers “a general framework in which additional and context specific explanations may be placed” (Aldrich et al. 2008:591). Evolutionary models, for example, can explain why cultural elaboration would evolve, but they cannot account for particular expressions or levels of elaboration, which are historically contingent phenomena. Continued collaboration and cross-fertilization among researchers in fields as diverse as climatology, ecology, osteology, and psychology, hold promise for a more complete understanding of Darwinian processes, including the evolution of cultural behavior.

72 APPENDIX A. DATES OF INITIAL AND FINAL MONUMENTS BY SITE

Site First Final First legible Final legible Source legible legible dated dated dated dated monument monument monument monument (Long (Long (CE) (CE) Count) Count)

Aguacatal 751 9.16.0.0.0 Neiman 1997 Aguas 787 791 9.17.16.6.1 9.18.0.13.18 Lowe 1985; Calientes Neiman 1997 Aguataca 692 793 9.13.0.0.0 9.18.3.0.17 Neiman 1997 Altar de 455 771 9.1.0.0.0 9.17.0.0.0 Neiman 1997 Sacrificios Balakbal 406 406 8.18.9.17.18 8.18.9.17.18 Lowe 1985 Benque Viejo 849 849 10.1.0.0.0 Hamblin & Pitcher 1980 602 786 9.8.9.0.0 9.17.15.12.10 Neiman 1997 Calakmul 514 810 9.4.0.0.0 9.19.0.0.0 Lowe 1985 Cancuen 790 800 9.18.0.0.0 9.18.10.0.0 Lowe 1985; Neiman 1997 Caracol 514 849 9.4.0.0.0 10.1.0.0.0 Lowe 1985 Cerro de las 470 534 9.1.15.0.0 9.5.0.0.0 Hamblin & Mesas Pitcher 1980 Chinikiha 615 615 9.9.2.8.4 9.9.2.8.4 Lowe 1985 591 844 9.7.17.12.14 10.0.15.0.0 Lowe 1985 613 684 9.9.0.0.0 9.12.12.0.5 Hamblin & Pitcher 1980 Comalcalco 814 814 9.19.3.13.12 Neiman 1997 Comitan 874 874 10.2.5.0.0 10.2.5.0.0 Lowe 1985 Copan 465 822 9.1.10.0.0 9.19.11.14.5 Neiman 1997 662 742 9.11.10.0.0 9.15.10.17.15 Neiman 1997 El Amparo 665 665 9.11.13.0.0 9.11.13.0.0 Lowe 1985 El Caribe 780 780 9.17.10.0.0 9.17.10.0.0 Lowe 1985 El Cayo 751 792 9.16.0.2.16 9.18.1.12.16 Neiman 1997 761 761 9.16.10.0.0 Neiman 1997 El Encanto 598 598 9.8.4.9.1 9.8.4.9.1 Lowe 1985 El Palmar 711 884 9.14.0.0.0 10.2.15.0.0 Lowe 1985

(continued next page) 73

Site First Final First legible Final legible Source legible legible dated dated dated dated monument monument monument monument (Long (Long (CE) (CE) Count) Count) El Pebellon 633 633 9.10.0.0.0 9.10.0.0.0 Lowe 1985 El Peru 790 790 9.18.0.0.0 Neiman 1997 El Zapote 378 378 8.17.1.5.3 8.17.1.5.3 Lowe 1985 Etzna 672 800 9.12.0.0.0 9.18.10.0.0 Hamblin & Pitcher 1980 Hatzcab Ceel 810 835 9.19.0.0.0 10.0.5.0.0 Hamblin & Pitcher 1980 Holactun 764 764 9.16.13.0.0 9.16.13.0.0 Hamblin & Pitcher 1980 Ichpaatun 593 593 9.8.0.0.0 9.8.0.0.0 Lowe 1985 Itsimte-Sacluk 761 775 9.15.0.0.0 9.17.5.0.0 Lowe 1985 736 830 9.15.4.15.3 9.19.19.16.0 Neiman 1997 780 800 9.17.9.10.13 9.18.10.0.0 Lowe 1985 859 879 10.1.10.0.0 10.2.10.0.0 Lowe 1985 780 780 9.17.10.0.0 9.17.10.0.0 Neiman 1997 Jaina 652 652 9.11.0.0.0 9.11.0.0.0 Hamblin & Pitcher 1980 Jimbal 879 889 10.2.10.0.0 10.3.0.0.0 Lowe 1985 Jonuta 790 790 9.18.0.0.0 Neiman 1997 Kuna-Lacanha 554 746 9.6.0.11.0 9.15.15.0.0 Lowe 1985 755 807 9.16.4.6.13 9.18.17.1.13 Neiman 1997 La Esperanza 593 593 9.8.0.0.0 9.8.0.0.0 Hamblin & Pitcher 1980 La Florida 731 766 9.15.0.0.0 9.16.15.0.0 Lowe 1985 La Honradez 771 790 9.17.0.0.0 9.18.0.0.0 Lowe 1985 785 805 9.17.15.0.0 9.18.15.0.0 Lowe 1985 La Milpa 780 780 9.17.10.0.0 9.17.10.0.0 Lowe 1985 La Muneca 781 889 9.17.10.10.0 10.3.0.0.0 Lowe 1985 Laguna Perdita 742 742 9.15.11.2.17 9.15.11.2.17 Neiman 1997 Los Higos 781 781 9.17.10.7.0 9.17.10.7.0 Lowe 1985 790 790 9.18.0.0.0 9.18.0.0.0 Neiman 1997 Machaquilla 711 841 9.14.0.0.0 10.0.10.17.5 Neiman 1997

(continued next page)

74

Site First Final First legible Final legible Source legible legible dated dated dated dated monument monument monument monument (Long (Long (CE) (CE) Count) Count) Morales 702 756 9.13.10.0.0 9.16.5.0.0 Neiman 1997 Mountain Cow 835 835 10.0.5.0.0 10.0.5.0.0 Neiman 1997 524 761 9.4.10.0.0 9.16.10.0.0 Lowe 1985 771 771 9.17.0.6.3 9.17.0.6.3 Neiman 1997 771 849 9.17.0.0.0 10.1.0.0.0 Neiman 1997 615 820 9.9.2.0.4 9.19.10.0.0 Lowe 1985 Nimli Punit 800 800 9.18.10.0.0 9.18.10.0.0 Neiman 1997 Ojo de Agua 588 588 9.7.15.0.0 9.7.15.0.0 Lowe 1985 475 475 9.2.0.0.0 9.2.0.0.0 Hamblin & Pitcher 1980 Oxpemul 687 830 9.12.15.0.0 10.0.0.0.0 Lowe 1985 Palenque 642 642 9.10.10.0.0 9.17.13.0.7 Neiman 1997 Pestac 665 665 9.11.12.9.6 9.11.12.9.6 Lowe 1985 Piedras Negras 435 810 9.0.0.0.0 9.19.0.0.0 Lowe 1985 Poco Uinic 790 790 9.18.0.0.0 9.18.0.0.0 Lowe 1985 Polol 777 790 9.17.7.0.4 9.18.0.0.0 Lowe 1985 Pomona 692 790 9.13.0.0.0 9.18.0.0.0 Lowe 1985 593 731 9.8.0.0.0 9.15.0.0.0 Lowe 1985 Quen Santo 869 879 10.2.0.0.0 10.2.10.0.0 Lowe 1985 Quexil 692 692 9.13.0.0.0 9.13.0.0.0 Lowe 1985 Quirigua 478 810 9.2.3.8.0 9.19.0.0.0 Lowe 1985 Sacchana 874 879 10.2.5.0.0 10.2.10.0.0 Hamblin & Pitcher 1980 Sacul 790 790 9.18.0.0.0 9.18.0.0.0 Neiman 1997 746 889 9.15.15.0.0 10.3.0.0.0 Lowe 1985 Tamarindito 762 762 9.16.11.7.13 9.16.11.7.13 Neiman 1997 Tayasal 805 869 9.18.15.0.0 10.2.0.0.0 Lowe 1985 Tikal 292 869 8.12.14.8.15 10.2.0.0.0 Lowe 1985 Tila 685 830 9.12.13.0.0 10.0.0.0.0 Lowe 1985 Tonina 495 909 9.3.0.0.0 10.4.0.0.0 Lowe 1985 603 711 9.8.10.0.0 9.14.0.0.0 Lowe 1985 Tzendales 691 691 9.12.19.1.1 9.12.19.1.1 Lowe 1985

(continued next page)

75

Site First Final First legible Final legible Source legible legible dated dated dated dated monument monument monument monument (Long (Long (CE) (CE) Count) Count) Tzibanche 559 909 9.6.5.0.0 10.4.0.0.0 Lowe 1985 Tzimin Kax 810 835 9.19.0.0.0 10.0.5.0.0 Lowe 1985 328 889 8.14.10.13.15 10.3.0.0.0 Lowe 1985 849 849 10.1.0.0.0 10.1.0.0.0 Lowe 1985 Uolantun 410 410 8.18.13.5.11 8.18.13.5.11 Lowe 1985 613 751 9.9.0.0.0 9.16.0.0.0 Lowe 1985 Walter Randal 864 864 10.1.14.9.17 10.1.14.9.17 Lowe 1985 Xultun 337 889 8.15.0.0.0 10.3.0.0.0 Lowe 1985 849 849 10.1.0.0.0 10.1.0.0.0 Lowe 1985 Yaxchilan 435 808 9.0.0.0.0 9.18.17.13.14 Neiman 1997 Yaxha 357 796 8.16.0.0.0 9.18.5.16.4 Neiman 1997

76 APPENDIX B. LAKE CHICHANCANAB CLIMATE DATA

Data abstracted from: Hodell, D.A. et al., 2001, Lake Chichancanab Isotope and Mineralogy Data, IGBP GES/World Data Center A for Paleoclimatology Data Contribution Series #2001-014. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

Originally published in Hodell, D. A., J. H. Curtis, and M. Brenner (1995). Possible Role of Climate in the Collapse of the Classic Maya Civilization. Nature 375:391-394.

18 Calendar Age (BCE/CE) % CaCO3 % S δ O Pyrgophorus -1986 61.92 2.11 1.79 -1965 65.00 2.33 0.79 -1955 86.92 1.01 0.50 -1944 43.17 3.39 0.40 -1924 53.00 3.36 1.77 -1914 65.92 2.91 2.06 -1893 54.42 3.01 1.67 -1883 62.17 2.79 2.56 -1862 62.92 1.81 2.21 -1852 75.83 1.57 1.43 -1831 78.92 1.81 2.41 -1811 73.92 1.58 1.49 -1801 42.42 3.23 1.16 -1780 44.42 3.05 0.65 -1770 85.58 0.83 1.35 -1749 85.00 1.04 1.57 -1729 55.42 2.31 -0.47 -1708 84.67 1.03 1.74 -1688 90.58 0.85 2.16 -1677 81.42 1.27 2.12 -1657 58.17 2.98 -1636 25.50 4.03 1.5 0 -1626 70.58 2.17 1.72 -1616 58.92 2.17 1.43 -1595 60.08 2.62 1.16 -1575 54.00 2.79 1.87 -1554 71.58 2.27 2.18 -1533 53.58 2.37 2.06

(continued next page)

77

18 Calendar Age (BCE/CE) % CaCO3 % S δ O Pyrgophorus -1528 -1523 59.42 1.26 2.07 -1513 -1503 67.67 2.29 1.75 -1487 -1482 57.58 2.56 0.93 -1477 -1472 84.58 0.95 1.00 -1451 71.33 2.14 0.35 -1441 59.25 2.79 0.24 -1431 76.08 1.53 1.00 -1410 86.67 0.72 0.84 -1390 87.92 0.59 1.60 -1369 92.58 0.78 1.45 -1364 -1359 79.42 1.13 1.58 -1354 -1349 92.92 0.62 1.84 -1328 90.83 0.58 0.30 -1322 1.47 -1318 91.5 0 -1312 0.58 -1307 91. 50 0.61 -0.17 -1287 91.83 0.52 1.80 -1277 88.50 0.76 1.73 -1266 81.50 0.95 -0.77 -1246 88.00 0.70 0.79 -1225 82.92 0.98 1.19 -1205 93.17 0.59 1.23 -1184 88.08 0.71 1.50 -1164 86.17 0.76 1.53 -1143 66.33 2.09 1.08 -1133 71.58 1.83 1.04 -1128 61.08 2.19 2.12

(continued next page)

78

18 Calendar Age (BCE/CE) % CaCO3 % S δ O Pyrgophorus -979 51.92 2.79 2.93 -958 58.58 2.87 2.57 -938 63.42 2.32 1.87 -917 60.08 2.37 1.17 -896 57.58 2.26 -876 69.83 2.15 2.16 -855 58.00 2.73 2.47 -835 63.50 2.13 1.23 -814 67.08 1.90 1.09 -794 39.33 3.21 2.16 -773 60.08 2.26 2.25 -753 68.58 1.87 1.87 -732 61.00 1.48 1.62 -711 93.75 0.63 -0.12 -691 95.08 0.48 -0.64 -670 53.58 3.04 1.69 -650 24.17 4.25 1.82 -629 56.58 2.96 2.61 -609 52.33 3.44 1.76 -588 35.75 3.94 2.32 -568 59.00 2.17 2.55 -547 52.42 3.12 2.56 -527 42.50 3.36 -0.59 -506 41.17 4.07 -485 45.58 3.19 0.15 -465 76.75 1.87 0.99 -444 56.25 3.06 2.39 -424 60.92 2.35 0.25 -403 36.92 4.06 2.38 -383 65.68 2.41 1.28 -362 9.83 5.39 1.75 -342 17.75 4.53 1.45 -321 46.00 3.60 3.39 -300 33.42 3.77 1.05

(continued next page)

79

18 Calendar Age (BCE/CE) % CaCO3 % S δ O Pyrgophorus -280 27.17 4.38 2.14 -259 39.50 5.93 2.00 -239 24.00 12.60 1.21 -218 15.58 12.63 2.03 -198 9.67 12.01 2.40 -177 14.92 8.09 2.04 -157 18.83 8.05 1.37 -136 26.58 8.03 2.78 -116 16.17 8.01 1.98 -95 16.00 7.51 2.76 -74 3.17 8.48 2.74 -54 7.33 7.43 2.93 -33 11.83 6.46 2.09 -13 17.33 6.05 3.07 8 29.42 5.85 1.15 28 11.00 7.41 2.46 49 30.92 4.87 3.00 69 30.75 4.84 1.76 90 14.67 6.02 3.62 111 10.00 7.67 1.30 131 54.92 2.80 2.07 152 12.75 10.1 0.99 172 22.17 7.61 3.62 193 57.08 6.23 0.89 213 62.58 2.14 2.70 234 29.33 2.21 1.96 254 36.50 6.51 1.56 275 48.42 3.28 -0.49 295 34.75 2.62 2.93 316 29.50 4.21 2.59 337 25.17 2.99 3.09 357 47.83 4.57 2.00 378 45.67 2.05 2.23 398 25.42 3.47 2.88

(continued next page)

80

18 Calendar Age (BCE/CE) % CaCO3 % S δ O Pyrgophorus 419 19.75 5.29 1.86 439 13.08 7.74 1.73 460 9.50 7.82 2.61 480 30.83 8.17 2.35 501 35.08 6.41 3.03 522 35.25 5.64 2.43 542 35.33 4.27 2.58 563 29.33 5.25 3.01 583 34.83 4.46 2.20 604 22.33 6.08 2.08 624 35.00 6.00 1.62 645 11.25 9.06 3.08 665 24.08 6.23 3.20 686 22.25 5.59 2.18 706 28.08 7.21 3.07 727 21.33 8.63 3.07 748 36.00 6.61 0.75 768 11.33 8.66 2.21 789 7.08 11.59 2.53 809 9.58 14.63 2.55 830 32.33 6.78 3.65 850 17.33 9.38 3.22 871 891 1.17 16.35 3.27 912 7.17 14.96 3.52 929 27.50 4.75 3.24 945 23.58 5.20 3.34 962 24.83 3.97 3.61 979 31.33 3.42 3.35 995 60.92 4.02 0.91 1012 40.00 2.98 1.58 1028 46.75 3.27 2.40 1045 57.17 1.53 2.73 1062 46.42 2.68 2.66

(continued next page)

81

18 Calendar Age (BCE/CE) % CaCO3 % S δ O Pyrgophorus 1078 44.17 3.05 3.26 1095 42.42 2.27 1.36 1112 46.33 2.35 2.95 1128 45.75 2.50 1.37 1145 41.92 2.82 3.49 1161 51.42 2.51 2.13 1178 39.33 3.18 2.97 1195 44.50 2.11 2.62 1211 34.35 3.11 1.11 1228 45.25 2.38 2.78 1245 31.75 2.70 2.50 1261 30.25 3.69 3.48 1278 48.50 2.3 1.14 1294 33.92 2.87 2.29 1311 56.17 1.77 3.28 1328 50.50 2.74 2.09 1344 36.92 3.05 2.64 1361 36.92 2.00 2.26 1378 51.67 4.07 2.24 1394 43.08 2.36 1411 78.83 2.47 1428 41.08 2.06 1444 45.17 1.71 1461 60.75 3.84 1.27 1477 37.33 3.89 2.02 1494 41.25 3.08 1.83 1511 48.83 2.15 1.53 1527 45.08 3.66 1.41 1544 32.83 3.46 2.58 1561 29.92 3.47 2.01 1577 32.50 2.70 3.01 1594 30.75 3.34 2.48 1610 54.25 2.30 2.45 1627 48.33 2.49 2.52

(continued next page)

82

18 Calendar Age (BCE/CE) % CaCO3 % S δ O Pyrgophorus 1644 66.25 0.87 3.16 1660 35.42 3.10 2.27 1677 29.75 3.16 2.58 1694 34.17 2.52 2.37 1710 47.25 2.31 2.38 1727 35.33 2.83 2.46 1744 43.58 2.04 1.63 1760 39.50 2.43 2.57 1777 43.42 1.70 2.22 1793 42.75 1.83 2.64 1810 22.33 2.40 1827 1843 0.8 0 1860 33.08 1.64 1877 27.58 2.67 1893 26.58 2.76 1910 23.25 1.22 1926 36.08 3.02 1943 35.42 2.37 1960 10.75 1.57 1976 5.08

83 APPENDIX C. POPULATION GROWTH IN SELECTED LOWLAND MAYA SITES

Relative population as percentage of maximum population (unadjusted figures) Middle Late Early Late Terminal Early Site Preclassic Preclassic Classic Cassic Classic Postclassic Central Tikal 2 21 78 98 14 4 Peripheral Tikal 1 8 100 66 20 1 Tayasal/Paxcaman 7 100 42 51 89 32 Yaxha/Sacnab 13 29 46 100 11 8 Belize River 52 93 50 100 50 21

Relative population as percentage of maximum population (figures adjusted for 150-year platform use) Middle Late Early Late Terminal Early Site Preclassic Preclassic Classic Cassic Classic Postclassic Central Tikal 1 17.7 34 97.5 14 3 Peripheral Tikal 1 5.5 64 98 29 1 Tayasal/Paxcaman 4 56 78 95 100 36 Yaxha/Sacnab 11 15 39 100 19 8 Belize River 39 33 43 100 98 13

Data are excerpted from Rice and Culbert (1990:34-45), with interpolations in cases where two or more complexes occur within a single period.

84 REFERENCES

Abrams, Elliot M. (1987). Economic Specialization and Construction Personnel in Classic Period Copan, Honduras. American Antiquity 52(3): 485-499.

_____ (1989). Architecture and Energy: An Evolutionary Perspective. Archaeological Method and Theory 1: 47-87.

_____ (1994). How the Maya Built Their World: Energetics and Ancient Architecture. Austin: University of Texas Press.

Abrams, Elliot M., and David J. Rue (1988). The Causes and Consequences of Deforestation among the Prehistoric Maya. Human Ecology 16(4): 377-395.

Adams, Richard E. W., William E. Brown, Jr., and T. Patrick Culbert (1981). Radar Mapping, Archaeology, and Ancient Maya Land Use. Science 213: 1457-1463.

Adams, Richard E. W., T. Patrick Culbert, Walter E. Brown, Jr., Peter D. Harrison, Laura J. Levi (1990). Rebuttal to Pope and Dahlin. Journal of Field Archaeology 17: 241-244.

Aldrich, Howard E. Geoffrey M. Hodgson, David L. Hull, Thorbjørn Knudsen, Joel Mokyr, Viktor J. Vanberg (2008). In Defence of Generalized Darwinism. Journal of Evolutionary Economics 18: 577-596.

Allen, Melinda S. (2004). Bet-hedging Strategies, Agricultural Change, and Unpredictable Environments: Historical Development of Dryland Agriculture in Kona, Hawaii. Journal of Anthropological Archaeology 23: 196-224.

Altschuler, Milton (1958). On the Environmental Limitations of Mayan Cultural Development. Southwestern Journal of Anthropology 14(2): 189-198.

Andrews, Anthony P. (1984). Long-Distance Exchange Among the Maya: A Comment on Marcus. American Antiquity 49(4): 826-828.

Anselmetti, Flavio S., David A. Hodell, Daniel Ariztegui, Mark Brenner and Michael F. Rosenmeier (2007). Quantification of Soil Erosion Rates related to Ancient Maya Deforestation. Geology 35: 915-918.

Aranyosi, E. F. (1999). Wasteful Advertising and Variance Reduction: Darwinian Models for the Significance of Nonutilitarian Architecture. Journal of Anthropological Archaeology 18(3): 356-375.

Beach, Timothy, Sheryl Luzzadder-Beach, Nicholas Dunning, and Duncan Cook (2008). Human and Natural Impacts on Fluvial and Karst Depressions of the Maya Lowlands. Geomorphology 101: 308–331.

85 Beach, T., N. Dunning, S. Luzzadder-Beach, D. E. Cook, J. Lohse (2006). Impacts of the Ancient Maya on Soils and Soil Erosion in the Central Maya Lowlands. Catena 65: 166- 178.

Beach, Timothy, Sheryl Luzzadder-Beach, Nicholas Dunning, Jon Hageman, and Jon Lohse (2002). Upland Agriculture in the Maya Lowlands: Ancient Maya Soil Conservation in Northwestern Belize. Geographical Review 92(3): 372-397.

Beer, J., W. Mende, and R. Stellmacher (2000). The Role of the Sun in Climate Forcing. Quaternary Science Reviews 19: 403415.

Bird, Douglas W., and James F. O’Connell (2006). Behavioral Ecology and Archaeology Journal of Archaeological Research 14:143-188.

Boone, James L. (1998). The Evolution of Magnanimity: When Is It Better To Give Than To Receive? Human Nature 9(1): 1-21.

Boone, James L., and Karen L. Kessler (1999). More Status or More Children?: Social Status, Fertility Reduction, and Long-Term Fitness. Evolution and Human Behavior 20: 257-277.

Boone, James L., and Eric Alden Smith (1998). Is It Evolution Yet?: A Critique of Evolutionary Archaeology. Current Anthropology 39(2): S141-S173.

Boserup, Ester (1965). The Conditions of Agricultural Growth: The Economics of Agrarian Change under Population Pressure. Chicago: Aldine.

Bove, Frederick J. (1981). Trend Surface Analysis and the Lowland Classic Maya Collapse. American Antiquity 46(1): 93-112.

Brenner, Mark, Michael F. Rosenmeier, David A. Hodell, and Jason H. Curtis (2002). Paleolimnology of the Maya Lowlands: Long-term Perspectives on Interactions among Climate, Environment, and Humans. Ancient Mesoamerica 13: 141-157.

Bronson, Bennett (1966). Roots and the Subsistence of the Ancient Maya. Southwestern Journal of Anthropology 22(3): 251-279.

Burnett, Richard L., Richard E. Terry, Marco Alvarez, Christopher Balzotti, Timothy Murtha, David Webster, Jay Silverstein (2011). The Ancient Agricultural Landscape of the Satellite Settlement of Ramonal Near Tikal, Guatemala. Quaternary International (in press).

Campbell, Donald T. (1974). Evolutionary Epistemology. In The Philosophy of Karl Popper, Book 1. P. A. Schlipp, ed. La Salle, Illinois: Open Court, 413-463.

Cavalli-Sforza, Luigi L. (1986). Cultural Evolution. American Zoologist 26(3): 845-855.

86 _____ (1998). Scale and Intensity in Classic Period Maya Agriculture: Terracing and Settlement at the ‘Garden City’ of Caracol, Belize. Culture and Agriculture 20(2/3): 60-77.

Chase, Arlen F., Diane Z. Chase, J. F. Weishampel, J. B. Drake, R. L. Shrestha, K. C. Slatton, J. J. Awe, W. E. Carter (2011). Airborne LiDAR, archaeology, and the ancient Maya landscape at Caracol, Belize. Journal of Archaeological Science 38: 387-398.

Chase, Diane Z. (1997). Southern Lowland Maya Archaeology and Human Skeleton Remains: Interpretations from Caracol (Belize), Santa Rita (Corozal (Belize), and Tayasal (Guatemala). In Bones of the Maya. S. L. Whittington and D. M. Reed, eds. Washington, DC: Smithsonian Institution Press: 15-27.

Chase, Arlen F., Diane Z. Chase, John F. Weishampel, Jason B. Drake, Ramesh L. Shrestha, K. Clint Slatton, Jaime J. Awe, William E. Carter (2011). Airborne LiDAR, Archaeology, and the Ancient Maya Landscape at Caracol, Belize. Journal of Archaeological Science 38: 387-398.

Chudek, Maciej, and Joseph Henrich (2011). Culture–Gene Coevolution, Norm-Psychology and the Emergence of Human Prosociality. Trends in Cognitive Sciences 15(5): 218-226.

Coe, Michael D. (1999a). Breaking the Maya Code. New York: Thames and Hudson.

_____ (1999b). The Maya. London: Thames and Hudson.

Cooke, C. Wythe (1931). Why the Cities of the Petén District, Guatemala, Were Abandoned. Journal of the Washington Academy of Sciences 21(13): 283-287.

Cowgill, Ursula M. (1961). Soil Fertility and the Ancient Maya. Transactions of the Connecticut Academy of Arts and Sciences 42: 1-56.

Curtis, Jason H., David A. Hodell, and Mark Brenner (1996). Climate Variability on the Yucatan Peninsula (Mexico) during the Past 3500 Years, and Implications for Maya Cultural Evolution. Quaternary Research 46: 37-47.

Curtis, Jason H., Mark Brenner, David A. Hodell, R. A. Balser, G. A. Islebe, and H. Hooghiemstra (1998). A Multi-Proxy Study of Holocene Environmental Change in the Maya Lowlands of Petén, Guatemala. Journal of Paleolimnology 19: 139–159.

Cziko, Gary (1995). Without Miracles: Universal Selection Theory and the Second Darwinian Revolution. Cambridge, Mass.: MIT Press.

Darwin, Charles (1871). The Descent of Man, and Selection in Relation to Sex. London: Murray.

Davis-Salazar, Karla L. (2006). Late Classic Maya Drainage and Flood Control at Copan, Honduras. Ancient Mesoamerica 17: 125-138.

87 Dawkins, Richard (2006). The Selfish Gene. 3rd ed. Oxford: Oxford University Press.

De Montmollin, Olivier (1995). Settlement and Politics in Three Classic Maya Polities. Madison, Wisc.: Prehistory Press.

Demarest, Arthur A. (1992). Ideology in Ancient Maya Cultural Evolution: The Dynamics of Galactic Polities. In Ideology and Pre-Columbian Civilizations. A. A. Demarest and G. W. Conrad, eds. Santa Fe: School of American Research Press, 135-157.

_____ (2004). Ancient Maya: The Rise and Fall of a Rainforest Civilization. Cambridge: Cambridge University Press.

Drennan, Robert D., Christian E. Peterson, and Jake R. Fox (2010). Degrees and Kinds of Inequality. In Pathways to Power: New Perspectives on the Emergence of Social Inequality, T. D. Price and G. M. Feinman, eds. New York: Springer, 45–76.

Dunnell, Robert C. (1980). Evolutionary Theory and Archaeology. Advances in Archaeological Method and Theory 3: 35-99.

_____ (1989). Aspects of the Application of Evolutionary Theory in Archaeology. In Archaeological Thought in America. M. H. Nitecki, ed. Chicago: University of Chicago Press, 35-49.

_____ (1999). The Concept of Waste in an Evolutionary Archaeology. Journal of Anthropological Archaeology 18(3): 243-250.

Dunnell, Robert. C., and Diana M. Greenlee (1999). Late Woodland Period ‘Waste’ Reduction in the Ohio River Valley. Journal of Anthropological Archaeology 18(3): 376-395.

Dunning, Nicholas P. (1996). A Reexamination of Regional Variability in the Pre-Hispanic Agricultural Landscape. In: The Managed Mosaic: Ancient Maya Agriculture and Resource Use. Scott L. Fedick, ed. Salt Lake City: University of Utah Press, 53-68.

Dunning, Nicholas P., and Timothy Beach (2004). Noxious or Nurturing Nature?: Maya Civilization in Environmental Context. In Continuities and Changes in Maya Archaeology: Perspectives at the Millennium. C. W. Golden and G. Borgstede, eds. New York: Routledge, 125-141.

_____ (2010). Farms and Forests: Spatial and Temporal Perspectives on Ancient Maya Landscapes. In Landscapes and Societies: Selected Cases. I. P. Martini and W. Chesworth, eds. Dordrecht: Springer.

Dunning, Nicholas P., Luzzadder-Beach, Sheryl, Timothy Beach, John G. Jones, Vernon Scarborough, and T. P. Culbert (2002). Arising from the Bajos: The Evolution of a Neotropical Landscape and the Rise of Maya Civilization. Annals of the Association of American Geographers 92(2): 267-283.

88

Dunning, Nicholas P., D. Wahl, Timothy Beach, J. Jones, and Sheryl Luzzadder-Beach (2007). Environmental Instability and Human Response in the Late Preclassic Southern Maya Lowlands. Paper presented at the annual meeting of the Society for American Archaeology, 28 April 2007, Austin Texas.

Dunning, Nicholas, Vernon Scarborough, Fred Valdez Jr., Sheryl Luzzadder-Beach, Timothy Beach & John G. Jones (1999). Temple Mountains, Sacred Lakes, and Fertile Fields: Ancient Maya Landscapes in Northwestern Belize. Antiquity 73: 650-660.

Emery, Kitty F. (2008). A Zooarchaeological Test for Dietary Resource Depression at the End of the Classic Period in the Petexbatun, Guatemala. Human Ecology 36: 617-634.

Emery, Kitty F., Lori E. Wright, Henry Schwarcz (2000). Isotopic Analysis of Ancient Deer Bone: Biotic Stability in Collapse Period Maya Land-Use. Journal of Archaeological Science 27: 537–550.

Enfield, David B., and Eric J. Alfaro (1999). The Dependence of Caribbean Rainfall on the Interaction of the Tropical Atlantic and Pacific Oceans. Journal of Climate 12: 2093-2103.

Fagan, Brian (2000). Floods, Famine, and Emperors: El Niño and the Fate of Civilization. New York: Basic Books.

Fedick, Scott L. (1995). Land Evaluation and Ancient Maya Land Use in the Upper Belize River Area, Belize, Central. Latin American Antiquity 6(1): 16-34.

_____ (1996). Introduction: New Perspectives on Ancient Maya Agriculture and Resource Use. In: The Managed Mosaic: Ancient Maya Agriculture and Resource Use. Scott L. Fedick, ed. Salt Lake City: University of Utah Press.

Fedick, Scott L., and Anabel Ford (1990). The Prehistoric Agricultural Landscape of the Central Maya Lowlands: An Examination of Local Variability in a Regional Context. World Archaeology 22(1): 18-33.

Field, Julie S. (2003). The Evolution of Competition and Cooperation in Fijian Prehistory: Archaeological Research in the Sigatoka Valley, Fiji. Ph.D. dissertation, University of Hawai‘i. Retrieved October 12, 2011, from Dissertations & Theses: Full Text database. (Publication No. AAT 3110010).

Ford, Anabel, and Ronald Nigh (2009). Origins of the Maya Forest Garden: Maya Resource Management. Journal of Ethnobiology 29(2): 213-236.

Freidel, Dorothy E., John G. Jones, and Eugenia Robinson (2011). Volcanic Eruptions, Earthquakes, and Drought: Environmental Challenges for the Ancient Maya People of the Antigua Valley, Guatemala. Yearbook of the Association of Pacific Coast Geographers 73: 15- 26.

89

Freiwald, Carolyn (2011). Maya Migration Networks: Reconstructing Population Movement in the Belize River Valley during the Late and Terminal Classic. Ph.D. dissertation, University of Wisconsin-Madison. Retrieved November 24, 2011, from Dissertations & Theses: Full Text database. (Publication No. 3471077).

French, Kirk D. (2007). Creating Space through Water Management at the Classic Maya Site of Palenque, Chiapas. In Palenque: Recent Investigations at the Classic Maya Center. Damien B. Marken, ed. Lanham: AltaMira Press, p. 123-132.

French, Kirk D., and Christopher J. Duffy (2010). Prehispanic Water Pressure: A New World First. Journal of Archaeological Science 37:1027–1032.

French, Kirk D., David S. Stuart, and Alfonso Morales (2006). Archaeological and Epigraphic Evidence for Water Management and Ritual at Palenque. In Precolumbian Water Management: Ideology, Ritual, and Power. Lisa J. Lucero and Barbara W. Fash, eds. Tucson, University of Arizona Press, p. 144-152.

Fry, Robert E. (1990). Disjunctive Growth in the Maya Lowlands. In Precolumbian Population History in the Maya Lowlands. T. P. Culbert and D. S. Rice, eds. Albuquerque: University of New Mexico Press, 285-300.

Gale, S. J. (2009). Dating the Recent Past. Quaternary Geochronology 4(5): 374-377.

Garrison, Thomas G., Bruce Chapman, Stephen Houston, Edwin Román, Jose Luis Garrido López (2011). Discovering Ancient Maya Settlements Using Airborne Radar Elevation Data. Journal of Archaeological Science 38: 1655-1662.

Gerry, John P., and Harold W. Krueger (1997). Regional Diversity in Classic Maya Diets. In Bones of the Maya. S. L. Whittington and D. M. Reed, eds. Washington, DC: Smithsonian Institution Press, 196-207.

Giannini, Alessandra, Yochanan Kushnir, and Mark A. Cane (2000). Interannual Variability of Caribbean Rainfall, ENSO, and the Atlantic Ocean. Journal of Climate 13: 297-311.

Gill, Richardson B. (2000). The Great Maya Droughts: Water, Life, and Death. Albuquerque: University of New Mexico Press.

Gill, Richardson B., Paul A. Mayewski, Johan Nyberg, Gerald H. Haug, and Larry C. Peterson (2007). Drought and the Maya Collapse. Ancient Mesoamerica 18: 283–302.

Grafen, Alan (1990). Biological Signals as Handicaps. Journal of Theoretical Biology 144(4): 517- 546.

_____. (1999). Formal Darwinism, the Individual-as-Maximizing Agent Analogy, and Bet- Hedging. Proceedings of the Royal Society of London 266: 799-803.

90

Gunn, Joel D., Ray T. Matheny, and William J. Folan (2002). Climate-Change Studies in the Maya Area: A Diachronic Analysis. Ancient Mesoamerica 13: 79-84.

Gunn, Joel D., John E. Foss, William J. Folan, Maria del Rosario Domínguez Carrasco, and Betty B. Faust (2002). Bajo Sediments and the Hydraulic System of Calakmul, Campeche, Mexico. Ancient Mesoamerica, 13: 297-315.

Hall, Brenda L., and Gideon M. Henderson (2001). Use of Uranium–Thorium Dating to Determine past 14C Reservoir Effects in Lakes: Examples from Antarctica. Earth and Planetary Science Letters 193: 565-577.

Halstead, Paul, and John O’Shea (1989). Introduction: Cultural Responses to Risk and Uncertainty. In Bad Year Economics: Cultural Responses to Risk and Uncertainty. P. Halstead and J. O’Shea, eds. Cambridge: Cambridge University Press, 1-7.

Hamblin, R. L., and B. L. Pitcher (1980). The Classic Maya Collapse: Testing Class Conflict Hypotheses. American Antiquity 45(2): 246-267.

Hamilton, F. E. (1999). Southeastern Archaic Mounds: Examples of Elaboration in a Temporally Fluctuating Environment? Journal of Anthropological Archaeology 18(3): 344-355.

Hammond, Norman, and Wendy Ashmore (1981). Lowland Maya Settlement: Geographical and Chronological Frameworks. In Lowland Maya Settlement Patterns. W. Ashmore, ed. Albuquerque: University of New Mexico Press, 19-36.

Hansen, Richard D., Steven Bozarth, John Jacob, David Wahl, and Thomas Schreiner (2002). Climatic and Environmental Variability in the Rise of Maya Civilization: A Preliminary Perspective from Northern Peten. Ancient Mesoamerica 13: 273-295.

Harrison, Peter D. (1977). The Rise of the Bajos and the Fall of the Maya. In Social Process in Maya Prehistory: Studies in Honour of Sir Eric Thompson. N. Hammond, ed. London: Academic Press, 470-508.

Haug, Gerald H., Detlef Günther, Larry C. Peterson, Daniel M. Sigman, Konrad A. Hughen, Beat Aeschlimann (2003). Climate and the Collapse of Maya Civilization. Science 299(5613): 1731-1735.

Haug, Gerald H. Konrad A. Hughen, Daniel M. Sigman, Larry C. Peterson, Ursula Röhl (2001). Southward Migration of the Intertropical Convergence Zone through the Holocene. Science 293: 1304-1308.

Haviland, William A. (1970). Tikal, Guatemala, and Mesoamerican Urbanism. World Archaeology 2(2): 186-198.

91 _____ (1972). Family Size, Prehistoric Population Estimates, and the Ancient Maya. American Antiquity 37(1): 135-139.

____ (2003). Settlement, Society, and Demography at Tikal. In Tikal: Dynasties, Foreigners, & Affairs of State. J. A. Sabloff, ed. Santa Fe: School of American Research Press, 111-142.

Healy, Paul F., Christophe G. B. Helmke, Jaime J. Awe, Kay S. Sunahara (2007). Survey, Settlement, and Population History at the Ancient Maya Site of Pacbitun, Belize. Journal of Field Archaeology 32: 17-39.

Henrich, Joseph (2004). Cultural Group Selection, Coevolutionary Processes and Large-Scale Cooperation. Journal of Economic Behavior & Organization 53: 3-35.

Hill, Kim, and Hillard Kaplan (1999). Life History Traits in Humans: Theory and Empirical Studies. Annual Review of Anthropology 28: 397-430.

Hodell, David A. (2001). Solar Forcing of Drought Frequency in the Maya Lowlands. Science 292: 1367-1370.

Hodell, David A., Jason. H. Curtis, and Mark Brenner (1995). Possible Role of Climate in the Collapse of Classic Maya Civilization. Nature 375: 391-394.

Hodell, David A., Mark Brenner, and Jason. H. Curtis (2005). Terminal Classic Drought in the Northern Maya Lowlands Inferred from Multiple Sediment Cores in Lake Chichancanab (Mexico). Quaternary Science Reviews 24: 1413-1427.

_____ (2007). Climate and Cultural History of the Northeastern Yucatan Peninsula, Quintana Roo, Mexico. Climatic Change 83: 215-240.

Hodell, David A., Rhonda L. Quinn, Mark Brenner, George Kamenov (2004). Spatial Variation of Strontium Isotopes (87Sr/86Sr) in the Maya Region: A Tool for Tracking Ancient Human Migration. Journal of Archaeological Science 31: 585-601.

Hull, David L. (2001). Science and Selection: Essays on Biological Evolution and the Philosophy of Science. 2nd ed. Cambridge: Cambridge University Press.

Hunt, B. G., and T. I. Elliott (2005). A Simulation of the Climatic Conditions Associated with the Collapse of the Maya Civilization. Climatic Change 69: 393-407.

Hunt, Terry L., and Carl P. Lipo (2001). Cultural Elaboration and Environmental Uncertainty in Polynesia. In Pacific 2000: Proceedings of the Fifth International Conference on Easter Island and the Pacific. C.M. Stevenson, G. Lee, and F. Morin, eds. Los Osos: Easter Island Foundation, 103-115.

_____ (2011). The Statues That Walked: Unraveling the Mystery of Easter Island. New York: Free Press.

92 Johnson, Kristofer D., David R. Wright, and Richard E. Terry (2007). Application of Carbon Isotope Analysis to Ancient Maize Agriculture in the Petexbatún Region of Guatemala. Geoarchaeology 22(3): 313-336.

Johnson, Patricia Lyons (1990). Changing Household Composition, Labor Patterns, and Fertility in a Highland New Guinea Population. Human Ecology 18(4): 403-416.

Johnston, Kevin J. (2003). The Intensification of Pre-industrial Cereal Agriculture in the Tropics: Boserup, Cultivation Lengthening, and the Classic Maya. Journal of Anthropological Archaeology 22: 126-161.

Kaplan, Hillard S., and Jane B. Lancaster (2003). An Evolutionary and Ecological Analysis of Human Fertility, Mating Patterns, and Parental Investment. In Offspring: Human Fertility Behavior in Biodemographic Perspective. K. W. Wachter and R. A. Bulatao, eds. Washington, D.C.: National Academies Press.

Kornbacher, Kimberly D. (1999). Cultural Elaboration in Prehistoric Coastal Peru: An Example of Evolution in a Temporally Variable Environment. Journal of Anthropological Archaeology 18(3): 282-318. Kornbacher, Kimberly D., and Mark E. Madsen (1999). Explaining the Evolution of Cultural Elaboration. Journal of Anthropological Archaeology 18(3): 241-242.

Kunen, Julie L. (2001). Ancient Maya Agricultural Installations and the Development of Intensive Agriculture in NW Belize. Journal of Field Archaeology 28(3/4): 325-346.

Kvamme, Kenneth L. (1990). Spatial Autocorrelation and the Classic Maya Collapse Revisited: Refined Techniques and New Conclusions. Journal of Archaeological Science 17: 197-207.

Lentz, David L. (1991). Maya Diets of the Rich and Poor: Paleoethnobotanical Evidence from Copan. Latin American Antiquity 2(3): 269-287.

Leyden, Barbara W. (2002) Pollen Evidence for Climatic Variability and Cultural Disturbance in the Maya Lowlands. Ancient Mesoamerica 13: 85–101.

Leyden, Barbara W., Mark Brenner, and Bruce H. Dahlin (1998). Cultural and Climatic History of Cobá, a Lowland in Quintana Roo, Mexico. Quaternary Research 49: 111–122.

Lowe, John W. G. (1985). The Dynamics of Apocalypse: A Systems Simulation of the Classic Maya Collapse. Albuquerque: University of New Mexico Press.

Madsen, Mark E. (2001). Evolutionary Bet-Hedging and the Hopewell Cultural Climax. In Posing Questions for a Scientific Archaeology. T. L. Hunt, C. P. Lipo, and S. L. Sterling, eds. Westport, Conn.: Bergin & Garvey, 279-305.

93 Madsen, Mark E., Carl Lipo, and Michael Cannon (1999). Fitness and Reproductive Trade- Offs in Uncertain Environments: Explaining the Evolution of Cultural Elaboration. Journal of Anthropological Archaeology 18(3): 251-281.

Magaña, Victor, Jorge A. Amador, and Socorro Medina (1999). The Midsummer Drought over Mexico and Central America. American Meteorological Society 12:1577-1588.

Marcus, Joyce (1983). Lowland Maya Archaeology at the Crossroads. American Antiquity 48(3): 454-488.

Márquez, Lourdes, and Andrés del Ángel (1997). Height among Prehispanic Maya of the Yucatán Peninsula: A Reconsideration. In Bones of the Maya. S. L. Whittington and D. M. Reed, eds. Washington, DC: Smithsonian Institution Press: 51-61.

Martin, Simon, and (2008). Chronicles of the Maya Kings and Queens: Deciphering the Dynasties of the Ancient Maya. 2nd ed. London: Thames & Hudson.

Massey, Virginia K., and D. Gentry Steele (1997). A Maya Skull Pit from the Terminal Classic Period, Colha, Belize. In Bones of the Maya. S. L. Whittington and D. M. Reed, eds. Washington, DC: Smithsonian Institution Press: 62-77.

McAnany, Patricia A. (1990). Water Storage in the Puuc Region of the Northern Maya Lowlands: A Key to Population Estimates and Architectural Variability. In Precolumbian Population History in the Maya Lowlands. T. P. Culbert and D. S. Rice, eds. Albuquerque: University of New Mexico Press, 263-284.

McAnany, Patricia A., and Gallareta Negrón, T. (2010). Bellicose Rulers and Climatological Peril?: Retrofitting Twenty-First Century Woes on Eighth-Century Maya Society. In The Choices and Fates of Human Societies: An Anthropological and Environmental Reader. N. Yoffee and P. A. McAnany, eds. Cambridge: Cambridge University Press, 142-175.

McNeil, Cameron L., David A. Burney, and Lida Pigott Burney (2010). Evidence Disputing Deforestation as the Cause for the Collapse of the Ancient Maya Polity of Copan, Honduras. PNAS 107(3): 1017–1022. Me-Bar, Yoav, and Fred Valdez Jr. (2003). Droughts as Random Events in the Maya Lowlands. Journal of Archaeological Science 30: 1599-1606.

Meggers, Betty J. (1954). Environmental Limitations on the Development of Culture. American Anthropologist 56: 801-824.

Morley, Sylvanus Griswold (1946). The Ancient Maya. Stanford: Stanford University Press.

Morley, Sylvanus G., and George W. Brainerd (1983). The Ancient Maya. 4th ed. revised by Robert J. Sharer. Stanford: Stanford University Press.

94 Moy, Christopher M., Geoffrey O. Seltzer, Donald T. Rodbell, and David M. Anderson (2002). Variability of El Niño/Southern Oscillation Activity at Millennial Timescales during the Holocene Epoch. Nature 420: 162-165.

Nations, James D., and Ronald B. Nigh (1980). The Evolutionary Potential of Lacandon Maya Sustained-Yield Tropical Forest Agriculture. Journal of Anthropological Research 36(1): 1-30.

Neff, Hector, Deborah M. Pearsall, John G. Jones, Barbara Arroyo de Pieters, Dorothy E. Freidel. (2006) Climate Change and Population History in the Pacific Lowlands of Southern Mesoamerica. Quaternary Research 65: 390-400.

Neiman, Fraser D. (1997). Conspicuous Consumption as Wasteful Advertising: A Darwinian Perspective on Spatial Patterns in Classic Maya Terminal Monument Dates. In Rediscovering Darwin: Evolutionary Theory in Archaeological Explanation. C. M. Barton and G. A. Clark, eds. Arlington, Va.: American Anthropological Association, 264-290.

Nolan, Kevin C., and Robert A. Cook (2010). An Evolutionary Model of Social Change in the Middle Ohio Valley: Was Social Complexity Impossible during the Late Woodland but Mandatory during the late Prehistoric? Journal of Anthropological Archaeology 29:62-79.

Nolan, Kevin C., and Steven P. Howard (2010). Using Evolutionary Archaeology and Evolutionary Ecology to Explain Cultural Elaboration: The Case of Middle Ohio Valley Woodland Period Ceremonial Subsistence. North American Archaeologist 31(2): 119-154.

Pohl, Mary. Kevin O. Pope, John G. Jones, John S. Jacob, Dolores R. Piperno, Susan D. deFrance, David L. Lentz, John A. Gifford, Marie E. Danforth, J. Kathryn Josserand (1996). Early Agriculture in the Maya Lowlands. Latin American Antiquity 7(4): 355-372.

Pope, Kevin O., and Bruce H. Dahlin (1989). Ancient Maya Wetland Agriculture: New Insights from Ecological and Remote Sensing Research. Journal of Field Archaeology 16: 87- 106.

_____ (1993). Radar Detection and Ecology of Ancient Maya Canal Systems—Reply to Adams et al. Journal of Field Archaeology 20: 379-383.

Poveda, Germán Poveda, Peter R. Waylen, and Roger S. Pulwarty (2006). Annual and Inter- annual Variability of the Present Climate in Northern South America and Southern Mesoamerica. Palaeogeography, Palaeoclimatology, Palaeoecology 234: 3- 27.

Premo, L. S. (2004). Local Spatial Autocorrelation Statistics Quantify Multi-scale Patterns in Distributional Data: An Example from Classic Maya Lowlands. Journal of Archaeological Science 31: 855-866.

95 Price, T. Douglas, James H. Burton, Paul D. Fullagar, Lori E. Wright, Jane E. Buikstra, Vera Tiesler (2008). Strontium Isotopes and the Study of Human Mobility in Ancient Mesoamerica. Latin American Antiquity 19(2): 167-180.

Proskouriakoff, Tatiana (1950). A Study of Classic Maya Sculpture. Washington, D.C.: Carnegie Institute of Washington.

Puleston, Dennis E. (1982). The Role of Ramon in Maya Subsistence. In Maya Subsistence: Studies in Memory of Dennis E. Puleston. K. V. Flannery, ed. New York: Academic Press, 353-336. Rathje, William L. (1971). The Origin and Development of Lowland Classic Maya Civilization. American Antiquity 36(3): 275-285.

Rice, Don S. (1993). Eighth-Century Physical Geography, Environment, and Natural Resources in the Maya Lowlands. In Lowland Maya Civilization in the Eighth Century A.D.: A Symposium at Dumbarton Oaks, 7th and 8th October 1989, J. A. Sabloff and J. S. Henderson, eds. Washington, D.C.: Dumbarton Oaks Research Library and Collection, 11-63.

Rice, Don S. (1996). Paleolimnological Analysis in the Central Peten, Guatemala. In: The Managed Mosaic: Ancient Maya Agriculture and Resource Use. Scott L. Fedick, ed. Salt Lake City: University of Utah Press, 193-206.

Rice, Don S., and Prudence M. Rice (1990). Population Size and Population Change in the Central Peten Lakes Region, Guatemala. In Precolumbian Population History in the Maya Lowlands. T. P. Culbert and D. S. Rice, eds. Albuquerque: University of New Mexico Press, 123-148.

Rice, Don S., and T. Patrick Culbert (1990). Historical Contexts for Population Reconstruction. In Precolumbian Population History in the Maya Lowlands. T. P. Culbert and D. S. Rice, eds. Albuquerque: University of New Mexico Press, 1-36.

Richerson, Peter J., Robert Boyd, and Joseph Henrich (2010). Gene-Culture Coevolution in the Age of Genomics. PNAS 107(suppl. 2): 8985-8992.

Riedinger, M. A., M. Steinitz-Kannan, W. M. Last, and M. Brenner (2002). A ~6100 14C yr Record of El Niño Activity from the Galápagos Islands. Journal of Paleolimnology 27: 1-7.

Rindos, David (1980). Symbiosis, Instability, and the Origins and Spread of Agriculture: A New Model. Current Anthropology 21(6): 751-772.

Rosenmeier, Michael F., David A. Hodell, Mark Brenner, Jason H. Curtis, and T. P. Guilderson (2002). A 4000-Year Lacustrine Record of Environmental Change in the Southern Maya Lowlands, Petén, Guatemala. Quaternary Research 57: 183-190.

96 Santley, Robert S. (1990). Demographic Archaeology in the Maya Lowlands. In Precolumbian Population History in the Maya Lowlands. T. P. Culbert and D. S. Rice, eds. Albuquerque: University of New Mexico Press, 325-343.

Santley, Robert S., Thomas W. Killion, and Mark T. Lycett (1986). On the Maya Collapse. Journal of Anthropological Research 42(2): 123-159.

Sarachik, Edward S., and Mark A. Cane (2010). The El Niño-Southern Oscillation Phenomenon. New York: Cambridge University Press.

Saul, Frank P., and Julie Mather Saul (1991). The Preclassic Population of Cuello. In Cuello: An Early Maya Community in Belize. N. Hammond, ed. Cambridge: Cambridge University Press: 134-158.

_____ (1997). The Preclassic Skeletons from Cuello. In Bones of the Maya. S. L. Whittington and D. M. Reed, eds. Washington, DC: Smithsonian Institution Press, 28-50.

Scarborough, Vernon L., and Gary G. Gallopin (1991). A Water Storage Adaptation in the Maya Lowlands. Science 251: 658-662.

Scarborough, Vernon L., M. E. Becher, J. L. Baker, G. Harris, and F. Valdez, Jr. (1995) Water and Land at the Ancient Maya Community of La Milpa. Latin American Antiquity 6(2): 98-119.

Scherer, Andrew K. (2007). Population Structure of the Classic Period Maya. American Journal of Physical Anthropology 132: 367-380.

Seger, Jon, and H. Jane Brockmann. (1987). What is Bet-Hedging? In Oxford Surveys in Evolutionary Biology. P. H. Harvey and L. Partridge, eds. Oxford: Oxford University Press, 182-211.

Sharer, Robert J. (2006). The Ancient Maya. Stanford, Calif.: Stanford University Press.

Shennan, Stephen (2002). Genes, Memes and Human History: Darwinian Archaeology and Cultural Evolution. New York: Thames & Hudson.

_____ (2008). Evolution in Archaeology. Annual Review of Anthropology 37: 75-91.

Siemens, Alfred H. (1978). Karst and the Pre-Hispanic Maya in the Southern Lowlands. In Pre-Hispanic Maya Agriculture. P. D. Harrison and B. L. Turner II eds. Albuquerque: University of New Mexico Press, 117-143.

Silverstein, Jay E., David Webster, Horacio Martinez, and Alvaro Soto (2009). Rethinking the Great Earthwork of Tikal: A Hydraulic Hypothesis for the Classic Maya Polity. Ancient Mesoamerica 20(1): 45-58.

97 Stahle, D. W., J. Villanueva Diaz, D. J. Burnette, J. Cerano Paredes, R. R. Heim Jr., F. K. Fye, R. Acuna Soto, M. D. Therrell, M. K. Cleaveland, and D. K. Stahle (2011). Major Mesoamerican Droughts of the Past Millennium. Geophysical Research Letters 38: L05703: 1-4.

Stephens, John Lloyd, and Frederick Catherwood (1854). Incidents of Travel in Central America, Chiapas, and Yucatan. London: A. Hall, Virtue & Co.

Sterling, Sarah (1999). Mortality Profiles as Indicators of Slowed Reproductive Rates: Evidence from Ancient Egypt. Journal of Anthropological Archaeology 18(3): 319-343.

Storey, Rebecca (2006). An Elusive Paleodemography?: A Comparison of Two Methods for Estimating the Adult Age Distribution of Deaths at Late Classic Copan, Honduras. American Journal of Physical Anthropology 132: 40-47.

Stuiver, Minze, and Thomas F. Braziunas (1993). Sun, Ocean, Climate and Atmospheric 14 CO2: An Evaluation of Causal and Spectral Relationships. The Holocene 3(4): 289-305.

Tankersley, Kenneth B., Vernon L. Scarborough, Nicholas Dunning, Warren Huff, Barry Maynard, Tammie L. Gerke (2011). Evidence for Volcanic Ash Fall in the Maya Lowlands from a Reservoir at Tikal, Guatemala. Journal of Archaeological Science 1-14.

Thompson, J. E. S. (1954). The Rise and Fall of Maya Civilization. Norman: University of Oklahoma Press.

____ (1971). Estimates of Maya Population: Deranging Factors. American Antiquity 36(2): 214-216.

Tourtellot, Gair, and Jeremy A. Sabloff (1972). Exchange Systems among the Ancient Maya. American Antiquity 37(1): 126-135.

Turner, B. L. II (1978). The Development and Demise of the Swidden Thesis of Maya Agriculture. In Pre-Hispanic Maya Agriculture. P. D. Harrison and B. L. Turner II eds. Albuquerque: University of New Mexico Press, 13-22.

Turner, B. L. II, and P. D. Harrison (1981). Prehistoric Raised-Field Agriculture in the Maya Lowlands. Science 213: 399-405.

Van Geel, B., O. M. Raspopov, H. Renssen, J. van der Plicht, V. A. Dergachev, and H. A. J. Meijer (1999). The Role of Solar Forcing upon Climate Change. Quaternary Science Reviews 18: 331-338.

Voland, Eckart (1998). Evolutionary Ecology of Human Reproduction. Annual Review of Anthropology 27: 347-374.

98 Wahl, David, Roger Byrne, Thomas Schreiner, and Richard Hansen (2006). Holocene Vegetation Change in the Northern Peten and its Implications for Maya Prehistory. Quaternary Research 65: 380-389.

Webb, Elizabeth A., Henry P. Schwarcz, and Paul F. Healy (2004). Detection of Ancient Maize in Lowland Maya Soils Using Stable Carbon Isotopes: Evidence from Caracol, Belize. Journal of Archaeological Science 31: 1039-1052.

Webb, Elizabeth A., Henry P. Schwarcz, Christopher T. Jensen, Richard E. Terry, Matthew D. Moriarty, and Kitty F. Emery (2007). Stable Carbon Isotope Signature of Ancient Maize Agriculture in the Soils of Motul De San José, Guatemala. Geoarchaeology 22(3): 291-312.

Webster, David (1985). Surplus, Labor, and Stress in Late Classic Maya Society Journal of Anthropological Research 41(4): 375-399.

_____ (2002). The Fall of the Ancient Maya: Solving the Mystery of the Maya Collapse. London: Thames & Hudson.

_____. (2009). Three Maya Settlement Projects and Some Implications. Unpublished. Prepared for the 2008 6th Palenque Mesa Redonda and subsequently updated.

_____ (2011 in press). Maya Drought and Niche Inheritance.

_____ (n.d.). The Uses and Abuses of the Ancient Maya. Prepared for the Emergence of the Modern World Conference, Otzenhausen, Germany, 2007.

Webster, David, and AnnCorrine Freter (1990). The Demography of Late Classic Copan. In Precolumbian Population History in the Maya Lowlands. T. P. Culbert and D. S. Rice, eds. Albuquerque: University of New Mexico Press, 37-61.

Webster, David, and J. Kirker (1995). Too Many Maya, Too Few Buildings: Investigating Construction Potential at Copan, Honduras. Journal of Anthropological Research 51(4): 363- 387.

Webster, David, AnnCorrine Freter, and Nancy Gonlin (2000). Copán: The Rise and Fall of an Ancient Maya Kingdom. Fort Worth: Harcourt College Publishers.

Webster, James W., George A. Brook, L. Bruce Railsback, Hai Cheng, R. Lawrence Edwards, Clark Alexander, and Philip P. Reeder (2007). Stalagmite Evidence from Belize Indicating Significant Droughts at the Time of Preclassic Abandonment, the Maya Hiatus, and the Classic Maya Collapse. Palaeogeography, Palaeoclimatology, Palaeoecology 250: 1- 17.

99 Weiss-Krejci, Estella, and Thomas Sabbas (2002). The Potential Role of Small Depressions as Water Storage Features in the Central Maya Lowlands. Latin American Antiquity 13(3): 343-357.

White, Christine D., and Henry P. Schwarcz (1989). Ancient Maya Diet as Inferred from Isotopic and Elemental Analysis of Human Bone. Journal of Archaeological Science 16(5): 451-474.

White, Christine D., Paul F. Healy, Henry P. Schwarcz (1993). Intensive Agriculture, Social Status, and Maya Diet at Pacbitun, Belize. Journal of Anthropological Research 49(4): 347-375.

Whittington, Steven L. (1989). Characteristics of Demography and Disease in Low-Status Maya from Classic Period Copan, Honduras. Ph.D. dissertation, The Pennsylvania State University. Retrieved November 20, 2008, from Dissertations & Theses: Full Text database. (Publication No. AAT 8922142).

_____ (1991). Detection of Significant Demographic Differences between Subpopulations of Prehispanic Maya from Copan, Honduras, by Survival Analysis. American Journal of Physical Anthropology 85: 167-184.

Whittington, Stephen L., and David M. Reed (1997). Commoner Diet at Copan: Insights from Stable Isotopes and Porotic Hyperostosis. In Bones of the Maya. S. L. Whittington and D. M. Reed, eds. Washington, DC: Smithsonian Institution Press, 157-170.

Wilken, Gene C. (1971). Food-Producing Systems Available to the Ancient Maya. American Antiquity 36(4): 432-448.

Willey, Gordon R. (1980). Towards an Holistic View of Ancient Maya Civilisation. Man 15(2): 249-266.

Williams, Jeff T. (1993). Spatial Autocorrelation and the Classic Maya Collapse: One Technique, One Conclusion. Journal of Archaeological Science 20: 705-709.

Wingard, John Davis (1992). The Role of Soils in the Development and Collapse of Classic Maya Civilization at Copan, Honduras. Ph.D. dissertation, The Pennsylvania State University. Retrieved November 21, 2008, from Dissertations & Theses: Full Text database. (Publication No. AAT 9226805).

Wood, James W. (1990). Fertility in Anthropological Populations. Annual Review of Anthropology 19: 211-242.

Wood, James W., George R. Milner, Henry C. Harpending, Kenneth M. Weiss (1992). The Osteological Paradox: Problems of Inferring Prehistoric Health from Skeletal Samples. Current Anthropology 33(4): 343-370.

100 Wright, David R., Richard E. Terry, and Markus Eberl (2009). Soil Properties and Stable Carbon Isotope Analysis of Landscape Features in the Petexbatún Region of Guatemala. Geoarchaeology 24: 466-491.

Wright, Lori E. (1997a). Biological Perspectives on the Collapse of the Pasión Maya. Ancient Mesoamerica, 8: 267-273.

____ (1997b). Ecology or Society?: Paleodiet and the Collapse of the Pasión Maya Lowlands. In Bones of the Maya. S. L. Whittington and D. M. Reed, eds. Washington, DC: Smithsonian Institution Press, 181-195.

_____ (1997c). Intertooth Patterns of Hypoplasia Expression: Implications for Childhood Health in the Classic Maya Collapse. American Journal of Physical Anthropology 102: 233-247.

____ (2004). Osteological Investigations of Ancient Maya Lives. In Continuities and Changes in Maya Archaeology: Perspectives at the Millennium. C. W. Golden and G. Borgstede, eds. New York: Routledge, 201-215.

____ (2005). Identifying Immigrants to Tikal, Guatemala: Defining Local Variability in Strontium Isotope Ratios of Human Tooth Enamel. Journal of Archaeological Science 32(4): 555-566.

Wright, Lori E., and Cassady J. Yoder (2003). Recent Progress in Bioarchaeology: Approaches to the Osteological Paradox. Journal of Archaeological Research 11(1): 43-70.

Wright, Lori E., and Francisco Chew (1998). Porotic Hyperostosis and Paleoepidemiology: A Forensic Perspective on Anemia among the Ancient Maya. American Anthropologist 100(4): 924-939.

Wrobel, Gabriel D. G (2004). Metric and Nonmetric Dental Variation among the Ancient Maya of Northern Belize. Ph.D. dissertation, Indiana University. Retrieved February 23, 2012, from Dissertations & Theses: Full Text database. (Publication No. AAT 3133869).

Yaeger, Jason, and David A. Hodell (2008). The Collapse of Maya Civilization: Assessing the Interaction of Culture, Climate, and Environment. In El Niño, Catastrophism, and Culture Change in Ancient America. D. H. Sandweiss and J. Quilter, eds. Washington, D.C.: Dumbarton Oaks, 187-242.

Zahavi, Amotz (1975). Mate Selection—A Selection for Handicap. Journal of Theoretical Biology 53: 205-214.

_____ (1997). The Cost of Honesty (Further Remarks on the Handicap Principle). Journal of Theoretical Biology 67: 603-605.

101