A “Marginality” Model to Explain Major Spatial and Temporal Gaps in the Old and New World Pleistocene Settlement Records

Karl W. Butzer Department of Geography, The Uniuersity of Teras 01 Austin

A key argument currently invoked to cast skepticism on certain South American sites. that suggest a first peopling of the New World by ca. 35,000 B.P., is the perplexingly low visibility of the archaeological record until 12,000 B.P. But, contrary to a popular misconception, great spatial and temporal discontinuities are common in the Old World settlement record. In Southern Africa, carefully controlled archaeological stratigraph- ies show that the now semiarid interior was unoccupied for 50,000 and more years at a time. Episodes of widespread settlement in marginal environments were relatively brief, limited to periods of substantially wetter climate, and closely linked with moist habitats. A risk-minimization model is proposed to explain these dincon- tinuities. Plant and animal resources in the region, given a climate as dry or drier than today, were of low productivity and low reliability for unspeeialized hunter-gatherers during the dry seasons of poor years. This would require large foraging territories and very wide spacing of proximal bands, so that the exchange of vital information on temporary or migratory resources was minimal. Finally, during extended droughts. fatdepleted animals provided an unsatisfactory source of fwd. These variables suggest that environments with low productiv- ity and predictability were too risky for unspeeialized hunter-gatherers with a pre-Upper Paleolithic technology, such as those who would have been able to enter the New World 35,000 B.P. Major spatial and temporal gaps in the New World settlement record should therefore be expected prior to the appearance of specialized Paleoindian hunter-gatherers ca. 12,000 B.P. Implications for geoarchaeological strategies are discussed.

INTRODUCTION hay and Collins, 1988; Collins and Dillehay, 1986 and personal communication, 1987). Stratigraph- There is mounting archaeological evidence ically lower than an incontrovertible archaeologi- from South America that makes it increasingly cal horizon with a regular set of square, wooden difficult to discount the presence of people in the structures, dated ca. 13,000B.P., is a unit of lami- New World by 35,000 B.P. One of these is a rock nated sand that seals an earlier horizon with two shelter, Pedra Furada, in northeastern and two dozen modified pebbles, originat- (Guidon and Delibrias, 1986; Guidon, 1984,1986, ing in an older, strongly weathered alluvial ter- and personal communication, 1988). Substantial race; several of these larger stones from the lower features, plausible but primitive stone ar- horizon, dated ca. 33,000 B.P., are unmistakable tifacts that lack evidence of blade technology, and artifacts? even fragments of ochre-smeared rock, have been Whether or not we are inclined to accept such dated back to 32,000years by 17 consistent radio- evidence, the low archaeological visibility of set- carbon dates.’ tlement earlier than 12,000B.P., remains a major The other is a low-energy fluvial site, Monte problem that demands explanation. If Paleolithic Verde, in Southern Chile (Dillehay, 1986; Dille- people were already present in the New World, why do there appear to be so few sites over such a ’ Dr. Nihde Guidon has kindly provided me with copies of the illustrated seetiom and artifad recovered through 1987. vast area, even if we include sites far more con- These carehlly documented excavations are currently down troversial than Pedra Furada and ? to one m below a level that has a new date of greater than The expectation of large numbers of prominent 39200 B.P. The background Bediment is a sand with abhdant line rubble and occasional rwf blocks. all derived sites-first met in North America with the Paleo- from the local sandstone, whereas the artifah are made indian phenomenon-is a function of Ameri- of quartz and quartzite. Two hearth mm lexes rich in laminated ash and dated to 17.000 B.P. and &000 B.P., have canista’ perception of the Old World record as one strong three-dimensional definition (up to 20 an thlck), mth of high and essentially continuous archaeological artifa& concentrated around them. A slab in the 17,000 B.P. horizon has two parallel red lines ainted on it. Blades and visibility, in both time and space. This is indeed micro-blades first appear after 8OOgB.P. most made of chert the case in some parts of Western Europe and the imported from some distance away p&ure-flaking is ht Near East. But in many regions of the Old World verified in the level dated 6200 B.P.The archaeological rofile mm ares closely with those of Pa&hic caves in europe an1 Africa and indicates repeated. high-intensity human occupation Ion before the advent of blade or pressure-flaking technokogies.Suggestions that the hearths Dr. Michael Collins allowed me to examine this mllection may reflect fomt fires and that the artifah are stream- which, in my mnsidered opinion, includes a range of piecea battered roelrs (Turner, 1986) are somewhat specious, that muld not poesibly have been udb non-human particularly for a shelter located 20 m up in a sandstone agencies. The *ology is re-Ey simiL to that of escarpment overlooking a broad pediment plain. mntemporaneous artifah in Pedra Furada.

Geoarchaeology: An International Journal,Vol. 3, No. 3, 193-203 (1988) 6 1988 by John Wiley & Sons, Inc. CCC 0883-6363/88/030193-11$04.00 A “MARGINALITY” MODEL the Paleolithic settlement record is remarkably PLEISTOCENE TECHNOCOMPLEXES IN THE spotty. SOUTHERN AFRICAN INTERIOR The object of this paper is to demonstrate how discontinuous this record can be, and to propose The study focus in southern Africa centers on explanations for this fact. the Vaal and upper Orange drainage basins, and Most of my fieldwork during the 1970s was de- more specifically where Precambrian andesitic la- voted to systematic geoarchaeological investiga- vas and Karoo-age intrusive volcanics are ex- tion of Pleistocene sites in southern Africa. This posed (Figures 1 and 2). These sources provided research was carried out with the benefit of prior andesite and hornfels (a contact metamorphic, experience with early sites in Spain and Egypt, also known as lydianite), two rock types providing and in the perspective of two seasons of work in quarry sources for lithic artifacts. These rocks the Rift Valley of East Africa. Some three dozen outcrop in what is a semiarid, grassy, erosional major previously excavated archaeological or fos- landscape, with many similarities to the Southern siliferous sites were studied in southern Africa, Plains of North America. The limited range of ranging from the australopithecine breccias to raw materials facilitates recognition of three suc- Later Stone Age sediments, and including Middle cessive technocomplexes (in the sense of Clarke, Stone Age surveys as well as examination of nu- 1978bthe Acheulian, the Middle Stone Age merous rock-art locations (Butzer et al., 1979; (MSA), and the Later Stone Age (MA). Butzer, 1982966-273; Butzer, 1984a,b). The Acheulian (see Volman, 1984; Sampson, This research effort, which included 13 months 1985) was characterized by large, bifacial hand- in the field and laboratory analysis of 4000 sedi- axes and cleavers, in addition to a range of side- ment samples, showed that an area of over struck flakes, with little or no evidence for pre- 200,000 square kilometers (26% the size of Texas) pared-platform cores. Almost aways, artifacts lacked human occupation for periods of over were made from the pale greenish and somewhat 50,000 years at a time. Specifically, Pleistocene coarse-grained andesite, exposed primarily in the settlement in the semiarid interior of Southern Tertiary and Pleistocene alluvial gravels of the Africa was limited to a series of relatively brief lower Vaal and middle Orange valleys. Somewhat and disjunct events, coincident with times of wet- distinctive, but still part of the regional ter climate, and separated by immense periods of Acheulian technocomplex, was the youngest in- time during which people evidently shunned mar- dustry of this type, correctly labelled Final ginal, semiarid, or arid environments. Acheulian, but more conveniently designated by

Figure 1. Southern Africa, showing location of key sites mentioned in text. Humid and subhumidareas are shaded. Key sites, from left to right WW, Wonderwerk; VR, Vaal-Riet floodplains; AL, Alex; FL, Florisbad; RCC, Rase Cottage Cave; BW, Bushman Rock Shelter and Heuningneskrans Cave; BC, Border Cave.

194 VOL. 3. NO. 3 A “MARGINALITY” MODEL

Figure 2. Middle Stone Age visibility in lower Vaal-middle Orange basin in the interior of Southern Africa (see frame in Figure 1). Site density in the Orange River Survey areas (Sampson, 1968) and the Seacow Basin (Sampson, 1985) exceeds the possibility of depiction at this scale. For the Alex area, see Figure 4. the regional name of Fauresmith. This terminal derives from a single stratigraphic unit and is of industry was notable for its smaller handaxes, of- roughly the same age. Specifically, the “Phase I” ten more slender or symmetrical, but also broader (type site Elandskloof 13), “Phase 11” (type site in profile, and for flakes sometimes struck from Orangia 1, shallow and possibly mixed with prepared-platform cores. There are also unifacial younger artifacts), and “Phase 111” (type site tools that approximate the profiles of a handaxe Zeekoegat 27) of Sampson (1968, but collapsed to and suggest a technological transition to the “Orangian” and “Zeekoegat” in Sampson, 1985), MSA. In most areas Fauresmith stone-knappers all come from the alluvial Riverton Formation, shifted almost exclusively to the use of hornfels, Member 111, in as far as they are “primary” (But- which favored a reduction of tool size, since veins zer, 1984a). Nonetheless, Zeekoegat collections of the black, fine-grained hornfels weather out as have minimal retouch, lack points or evidence of relatively small nodules. Levallois technology, have much higher blade ra- The Middle Stone Age lacks handaxes or tios, and are dominated by prismatic cores. The cleavers, and the most diagnostic artifacts are matter seems to suggest similarities to the prob- triangular points (typical frequencies 1%-6%), lem of partly coeval Mousterian “facies” in West- struck by convergent flaking from Levallois cores ern Europe (see Butzer, 1986), since the differ- and then trimmed unifacially. Also characteristic ences of patina are inconclusive-Zeekoegat is a variable but substantial proportion of blades being in a fine calcified sediment, and Orangia (10 to 30% or more), as well as a range of re- being in an oxidized, sandy matrix. At the Floris- touched tools, almost exclusively made of horn- bad spring site, an MSA occupation was found be- fels. The regional MSA conforms with Volman’s tween Peats 2 and 3 (Kuman and Clarke, 1986; (1984) “MSA 2” and, despite variation in facies, Butzer, 1988); these artifacts are compatible with

GEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL 195 A “MARGINALITY” MODEL the regional MSA. But a different MSA, with unu- LOCAL ARCHAEOLOGICAL sually high frequencies of retouched tools (the STRATIORAPHIES AND “Florisian” of Sampson, 1972), was encountered PALZOENVIRONMENTS in a lower stratigraphic unit, below Peat 2, mak- ing it somewhat older than the regional MSA Basic archaeostratigraphy is shown in Figure 3, complex; it is here labelled “Early,” aa distinct representing seven key sites or site complexes, ar- from “Late” MSA, and its occurrence is limited to ranged from southeast (Border Cave, on the Swa- the subhumid margins of the study area. ziland-Natal border) to northwest (Wonderwerk Peripheral to the andesite-hornfels outcrop re- Cave, northern Cape Province). This direction gion, MSA artifacta were made of other raw mate- also represents a precipitation gradient, from rials and are to some degree different. Early forms 1250 mm in the southeast to 300 mm in the north- of MSA are well represented in the more humid west. Vegetation today ranges from open, sub- parts of southern Africa, and there is also a dis- tropical woodland at Border Cave and Bushman tinctive industry, the Howieson’s Poort, which in- Rock, to a mosaic of grass and temperate wood- cludes large geometrice (Volman, 1984). land at Rose Cottage Cave, temperate grassland The Later Stone Age technocomplex is charac- at Florisbad, and subtropical savanna or bush to terized by high variability. The “Early” LSA con- the west of Alex. The columns represent local tains few formal, standardized, or retouched stratigraphies, calibrated to 40,000 or 50,000 tools, and sometimes includes little more than years by radiocarbon, and beyond that by extrapo- amorphous debitage; the subsequent Albany in- lated sedimentation rates, crosscorrelated by cli- dustry is more macrolithic in character and in- mato-stratigraphic criteria (Butzer, 1984a,b). Oc- cludes a variety of large circular and end- cupation levels are indicated in black (Figure 3). scrapers, as well as grinding stones; finally, the Border Cave represents the most complete MSA “Late” LSA is represented by the Smithfield, occupation sequence, spanning deep-sea oxygen marked by a high ratio of fully retouched, small isotope stages 3 to 6, with some weathering lacu- scrapers, and the microlithic Wilton, peripheral to nae or sterile levels (Butzer et al., 1978; Butzer, the study area, and notable for its dominant use of 1984b).“Bushman Rock” refers to two major sites, raw materials other than hornfels (see Deacon, near Ohrigatad, eastern Transvaal: Bushman 1984). The LSA collections lack characteristic Rock Shelter and Heuningneskrans Cave. Here MSA tool types and the Levallois technique was there is a long hiatus of 50,000 years between the no longer used. LSA and MSA (Butzer, 1984a,b), but the MSA Dating is discussed further below, but the basic occupations are difficult to classify (Volman, technocomplexes and industries can be summa- 1984). At Rose Cottage Cave (near Ladybrand, rized in Table I. Temporal contacts are time- Orange Free State) a series of essentially sterile transgressive in different parts of the subcon- deposits separate the LSA and MSA, representing tinent. The shift from Fauresmith to MSA may an archaeologicalbreak of over 30,000 years (But- have been gradational, although the MSA and zer, 1984a,b, with references). LSA are technologically very different. “Florisbad” (near Bloemfontein, Orange Free

Table I. Lithic technoeomplexea and industries in Southern Africa (after Volman, 1984; Deacon, 1984; Butzer et al., 1978; Butzer, 1978,1982,1984b: Sznbo and Butzer, 1979). Technmmplex/Indu&y Appmrimate Age Late LSA (Smithfield, Wilton) About 3600 B.P. to 19th century in study area,’beginning 8ooo B.P. elsewhere. Mid-LSA (Albany) About 13.000-6600 B.P. in study area, terminating 8000 B.P. elsewhere. Early LSA About 40,000-13,000 B.P. in study area, beginning 30,000 B.P. elsewhere. Late MSA Probably about 100,O00-90.000 B.P. in study area. but partly coeval with How- iwn’s Pwrt in humid Southern Africa: Late MSA may have begun earlier else- where, and persisted to 30,000 B.P. in Born plaees. Early MSA Perhap 176,000-116,000 B.P., not rep resented in immediate study ma. Final Acheulian (Fauresmith) Perhaps 260,000-176,000 B.P. Acheulian Probably prior to 300.000 B.P., extending back into Lower Pleiatofene. with a very dimntinuoun record.

198 VOL. 3. NO. 3 A “MARGINALITY” MODEL

ALEX mEL I 1(1*( ML ALOAC UBAW UIAW

tAaYLM

LATE MU LAN! MU -100,000

EARLY MU

URLV MU

Figure 3. Archaec-stratigraphy of key late1 Quaternary sites or site complexes in Southern Africa arranged in southeast (right) to northwest (IeA)order. For explanations, see text.

State) includes the hominid-bearing spring site of 15,000 and a moderately wet period of alluviation that name (Kuman and Clarke, 1986; Butzer, ca. 13,800-7800 B.P. (Member IVa) failed to at- 1988), the adjacent gully and nearby Modder Ri- tract settlement, but Smithfield sites are associ- ver alluvia (Butzer, 1984a), as well as another ated with marshy floodplain conditions ahr3000 spring at Vlakkraal. B.P. (Member IVb) (Butzer et al., 1979; Butzer, “Alex” refers to a complex of playa sites be- 1984a,b). tween Florisbad and Alexandersfontein (near Wonderwerk lies west of the region (near Ku- Kimberley, Northern Cape), including the farms ruman, Northern Cape), but as a major cave, pro- Deelpan, Voightspost, Uitzigt, Benfontein, and vides a yardstick for settlement on one periphery Mauritsfontein (Butzer,1984a,b). The last three of the region, as does Rose Cottage Cave on the of these were the subject of a survey and test exca- other. A palimpsest of MSA artifacts appears to be vations (Figure 4). The MSA is invariably associ- found between Acheulian deposits (below) and ated with heavily calcified spring accumulations Upper Pleistocene frost debris (above) (Beaumont or the lakeshores of much-expanded playas. A et a]., 1984); the latter includes traces of undiag- long period of deflation ensued, and even when nostic, presumably Early LSA artifacts between high lake levels and spring sedimentation re- levels dated by carbonized grass matting at ca. sumed a little before 20,000 B.P., these basins re- 39,000 and by hearths at 28,000 B.P? Erosion mained unoccupied for ten more millennia. Dur- prevailed within the cave from ca. 25,000-13,000 ing the early Holocene, some Albany settlement B.P., after which there is a more or less con- can be linked with seasonal playa lakes, but more tinuous settlement record of Albany and Wilton conspicuous settlement is only recorded after type (Butzer, 1984a,b, with references). 3500 B.P., when Smithfield peoples favored reac- Figure 3 summarizes the aggregate evidence of tivated springs where organic mucks accumu- a large array of excavated sites and extensive sur- lated. “Vaal and Riet” refers to the alluvial forma- tions of these two rivers and of the Modder, which have been extensively studied along many kilo- ’Whether or not there was a “primary” MSA level in Beau- meters of exposures. A few MSA sites are associ- mont’s excavation remains undocumented. Derived MSA points are found in L9A horizom datin about 12,OOO B.P. ated with the Riverton Formation, Member III, and +a debitage in ,the Units dated 3&JOO-28,000 B.P. ii but their scarcity suggests that seasonally- definitely not corn hble mth the flaking of Levaltois ints. The typolo of tR“, (derived)rta that I exapin$from inundated floodplains were not particularly at- Wonderwexis comparable m that of other, regonal “late” tractive; a period of soil formation ca. 19,000- MSA collections.

GEOARCHAEOLOGY:AN INTERNATIONAL JOURNAL 197 A “MARGINALITY” MODEL

Figure 4. Middle Stone Age sites recorded in the Alexandersfontein Basin and other such occurrences currently identifiedbetween the Van1 and Modder rivers (after Butzer, 1982 Fig. 14-4). The MSA groups that exploited Alex at the time of the expanded lake a.100,OOO B.P.pmbably ranged widely between the two riverine floodplains. vey. Except for Border Cave, there is a yawning Butzer, 1979; Butzer, 1984a), as well as in the hiatus of many tens of millennia between the adjacent Vaal and Riet valleys (Helgren, 1978; latest MSA and the earliest LSA, a break in set- Butzer, 1984a). Time scales are more inferential tlement that ranges from over 30,000 to almost for this Middle Pleistocene record, but sites are 80,000 years. The longest interruption is in the distinctly linked with moderately expanded lakes lower Vaal and middle Orange basin. Within the or broad floodplains with high-energy channels, same region, the record of even earlier settlement where gravel bars formed ideal quarries for stone- is equally discontinuous. Figure 5 provides an happing. overview of the spotty nature of Acheulian and The situation of the studied or surveyed sites is Fauresmith sites in the fossil lakes (Doornlaagte, informative in ita own right, as Table I1 shows. Rooidam) west of Alex (Butzer, 1974; Szabo and Acheulian “occurrences,))in the generic sense, ap-

198 VOL. 3, NO. 3 A “MARGINALITY” MODEL

LAKE BASINS RIVER VALLEYS

LATE MSA Mgi......

-174.000 BP’

......

ACHEULIAN Y ACHEULIAN t

0 a

Figure 5. Mid-Quatemary depositional sequences and Aeheulian/Fauresmith archaeological associations in the fossil lake basins and river valleys west of Alex and along the Vaal and Riet. The length of the columns is proportional to sedimentary thickness. Dating is limited to a uranium-series determination on the Rooidam sequence. ARer Butzer (1974, 1984a), Helgren (1978), and Szabo and Butzer (1979). pear to be closely tied to ready sources of raw ma- field evidence is primarily found on slopes and terial, but specific Fauresmith settlement focused ridges, relevant to hunting activities and increasingly on formerly active springs and sea- execution, with further preference for floodplains, sonally-wet floodplains. The MSA shows a distinct springs, and seasonal lakeshores. This pattern is shift to the shores of expanded lakes and prox- predicated on the particular range of habitats imity of then active springs. The Early LSA is available in the broader study area, a region of very rare and limited to caves around the periph- relatively limited relief. ery of the region. The Albany is also rare and For purposes of comparison, the results of an suggests a preference for springs. Finally, Smith- exhaustive, well-funded survey in a small basin,

GEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL 199 A “MARGINALITY” MODEL

Table 11. Preferred context of archaeological sites in the in- A RISK-MMIMIZATION HYPOTHESIS terior of Southern Africa (in numerical order with ample size in oarenthesea). The evidence for major spatial and temporal A. Alex and Vaal-Orange Area (Author) gaps in the Pleistocene settlement record of Acheulian (8) Braided channels, slopes (quarries) Southern Africa raises a fundamental question. Fauresmith (10) Spring. floodplain. quarry There always were some perennial streams and MSA (48) Lakeshore, spring, floodplain springs in the area, even during periods as dry as Early LSA (2) Cave Albany (3) Spring or drier than the present. Why, then, didn’t small Smithfield (69) Slope, floodplain, spring, lakeshore Paleolithic groups seek out such discontinuous B. Seacow Basin Survey (Sampson, 1985) habitats within the broader environmental mo- Acheulian (7) No data saic? I suggest that people avoided drier macro- Fauresmith (510) Quarry, riverine, spring environments because unspecialized hunter- MSA (968) Riverine. quarry. spring gatherers in prehistoric times preferred to avoid Early LSA Not identified Albany (1250) Quarry, riverine, spring risk. Smithfield (6624) Slope, spring, riverine (a) Given the high interannual variability of precipitation, plant foods during the dry seasons of poor years would have been characterized by low predictability as well as low net productivity. with considerable relief, that of the Seacow River A succession of dry years furthermore decimates (Sampson, 1985, see Fig. 2), are also included in the herds of medium and large-sized antelopes, Table II. Fossil lakes are a minor feature here, which eventually withdraw to moister grasslands and play only a limited role in site location. The in the east. The small springbok (AR~&IWSmr- concept of “riverine” does not correspond with our supidis) is a gazelle that thrives in the region “floodplain” sites, the former defined as within during relatively dry years, but it is very fleet and one km of relatively minor streams, the latter di- at 40 to 60 pounds weight, its pursuit provides rectly associated with a large, well-defined flood- little net caloric gain for hunters without the bow plain. Even allowing for these differences, it ap- and arrow, or snares and traps, or unfamiliar with pears that site preferences cannot be generalized, complex game drives. In addition, during pro- but reflect the range of available environmental tracted droughts, 19th century travellers report variation. What does emerge is that almost all that apringbok aggregated in huge migratory Pleistocene open-air living sites were linked to he& of several hundred thousand animals, that lakes now reduced to generally dry playas, would have left vast areas devoid of game. Such springs now defunct, or floodplains now en- low productivity and predictability of food and trenched. By comparison, late Holocene peoples, water resources would require an extremely high although still dependent on water availability, mobility response by unspecialized hunter- spread their activities over all parts of the land- gatherers (see Dyson-Hudson and Smith, 1978), scape in an expanded repertoire of activities. implying small bands (of under 50 people?), large Two primary conclusions can be drawn: (1) operational areas (many 1000 km’?),and very low Pleistocene settlement was remarkably discontin- population densities. uous in time and space, with repeated spans of (b) The radius of foraging territories or “opera- many tens of millennia during which the interior tional areas” of the Kalahari Bushmen at Dobe is of Southern Africa was essentially uninhabited about 16 km in an unusually productive environ- and unutilized, except for sporadic and peripheral ment, with protein-rich and reliable mongongo hunting forays; and (2) Pleistocene settlement nuts (see Yellen, 1976). If this radius were ex- was limited to periods of substantially moister cli- panded from 15 to 75 km for unspecialized hunter- mate and closely linked to dependable sources of gatherem in a much poorer setting, a roughly cir- water, although not all periods of moister climate cular operational area expands from about 700 to were accompanied by an expansion of settlement 17,500 km’, with a mean distance of 150 km be- into the interior. tween the centrally located camps of neighboring Two secondary inferences can be drawn by way bands, and space for only 11 such bands in an area of extension. Firstly, Pleistocene populations in of 200,000 km*. Such bands would have been the region appear to have been demographically spread so thinly that they would have had incom- very conservative, not necessarily responding to plete information on the state of resources within improved environmental resources by automatic their own operational area. With several dozen territorial expansion. And, secondly, late Holo- hunting forays per year, by groups of adult males, cene peoples had markedly improved technologies the probability is that members of a neighboring and organizational modes (also Deacon, 1984), band would have been fortuitously encountered that allowed more flexible demographic ad- only once every few years. But up-to-date infor- justment, coupled with effective settlement across mation on animal movements and the condition of the entire region. plant foods is eesential to hunters and, in quasi-

200 VOL. 3. NO. 3 A “MARGINALITY” MODEL isolation, a lack of such information is hazardous. and Pedra Furada, whose affinities are with the For bands on the fringes of such a thinly- older Paleolithic. inhabited area, there is an additional danger; As a provisional working hypothesis, two sepa- very small human populations need to exchange rate periods of late Pleistocene immigration to the mates and genes with other groups, in order to New World can be suggested. The first appears to remain biologically viable. have introduced people with a simple lithic tech- (c) During severe drought stress, game animals nology, limited to processing (as opposed to hunt- commonly lack body fat. Speth (1987)has assem- ing) tools, akin to the Asiatic “Middle” Paleo- bled a convincing body of data to show that starv- lithic. If this migration took place before 35,000 ing animals provide a poor and, at times, deadly B.P., there are as yet no documented sites of this diet for people suffering from acute famine. Fat- type and age in the United States, despite strong starved humans eating superlean meat crave for candidates in South America. The second would more, consuming protein to excess. This speeds up be the Paleoindian phenomenon, with an explo- the metabolic rate, and may lead to diarrhea, de- sion of sites notable for their fluted projectile hydration, and death within a week or two. This points and micro-blade technology, after about “fat-depletion model” cautions that starving 12,000 B.P., with intriguing antecedents at animals provide a poor or unsuitable source of Meadowcroft by 14,000 B.P. (Adovasio and Car- food at times of severe food stress. In other words, lisle, 1988). The Paleoindians were demograph- the true capacity of a drought-prone, low produc- ically expansive and skilled hunter-gatherers, tivity, and low predictability environment to sus- their lithics sharing many traits with those of the tain human life is a great deal less than its overall Asiatic Upper Paleolithic. resources-averaged over time and space-would The risk-minimization model, proposed here to suggest. explain major spatial and temporal discon- These ecological, informational, and biological tinuities in the African archaeological record, variables suggest that dry and unpredictable en- can be applied to geoarchaeological exploration vironments were too risky for early people. Being strategies for the New World. The African case conservative in their strategies, they probably study emphasized negative factors, concluding avoided marginal environments such as the semi- that semiarid or arid environments with low re- arid interior of Southern Africa, except during source predictability and reliability were unlikely times of ameliorated productivity. Such risk- to be inhabited in Pleistocene times. At the other prone environments will have, during the course end of the spectrum, the Middle Paleolithic Nean- of the Pleistocene, periodically expanded to cover derthals of Western Europe thrived in those sub- vast areas of the Old World, so favoring great arctic environments of southwestern France and temporal and spatial gaps in the settlement northern Spain (contra Diamond, 1987) where record. game was predictable and standing animal bio- mass high; these same people shunned most of the interior of the Iberian Peninsula, where large her- bivores were highly migratory (Butzer, IMPLICATIONS FOR NEW WORLD 1986). SElTLEMENT Regions must therefore first be identified, by various paleoecological criteria, where late Pleis- If the New World was first settled about 35,000 tocene resources would have been abundant and B.P. or so, during the intermediate glacial climate predictable, and where environmental hazards of deep-sea oxygen isotope stage 3, the human would not have been a major threat. Such condi- stock would probably have derived its technology tions would eliminate most of the Great Plains, from the older Paleolithic of eastern Asia. Despite where game resources have never been predict- considerable recent work (see Aikens and Hig- able. The valley systems of the Mountain West uchi, 1982; Rukang and Olsen, 1985; Chung and appear more suitable, although the revised plu- Pei, 1986; Larichev et al., 1987), Asian sites of vial lake chronologies now account for only a this general age are still few and of relatively low small part of Wisconsinan time. In effect, the visibility. Standardized tool types are at a pre- denser clusters of Paleoindian sites do not overlap mium, with choppers, chopping tools, rough bi- with environments likely to have attracted unspe- faces, trihedral picks (anomalously labelled cialized and vulnerable hunter-gatherers, thus re- “points”), and a variety of modified flakes. The quiring a search in different parts of the United earliest dated evidence for the prepared core tech- States. nique and a blade technology is about 21,000 B.P. Open-air sites will not be easy to locate in the (Japan), with pressure flaking (foliate points) in 40,000 to 15,000 year time span. Suitable sedi- evidence by 14,000 B.P. and a micro-blade tech- ments of the appropriate age must be exposed. nology shortly thereafter (China, Japan, North- Most of the studied alluvial sequences in the east Siberia). These Late Paleolithic innovations Southwest begin with terminal Wisconsinan, low- are absent from the older levels of Monte Verde energy deposits; earlier sediments are either frag-

GEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL 201 A “MARGINALITY‘ MODEL mentarily preserved or of much greater antiquity, the accepted age of earliest settlement on that and they tend to be high-energy, gravelly de- subcontinent from 10,000 to almost 33,000 years, posits, in which artifacts such as those of Pedra and a half-dozen other sites older than 20,000 B.P. Furada or Monte Verde would be very difficult to were located shortly thereafter. The key was to recognize. Lacustrine deposits will not be easier to know what to look for and where. Each of these examine since the highest lake stands are now breakthroughs came about when a new fact con- dated about 15,000 B.P. (see Thompson et al., vinced a number of pragmatic researchers to ex- 1986, with references), so that older shorelines plore alternative concepts. Possibly, completion are generally buried under later lake beds or were and publication of the excavations at Monte eroded during lake expansion. Backhoe trenching Verde and Pedra Furada will have a similar im- is an expensive, hit-or-miss proposition. Raised pact by illustrating what a “pre-Clovis”site looks beaches on mobile coasts are more promising, al- like. though cobble beaches were repeatedly quarried Disillusioned by a series of unconvincing by later peoples and coeval recognition “pre-Clovis” sites, Americanist archaeologists- will again pose severe challenges to all but a few understandably-tend to be conservative. But lithics specialists. Much the same applies to other skepticism can go too far. There now is a real dan- quarry sites. ger that new sites that do not conform with the Cave or shelter sites are undoubtedly the most conservative paradigm may be rejected out of promising, provided that sediments of appropriate hand by contrived arguments. We must, however, age are preserved-near the entrance, rather be prepared to accept the unexpected, provided than far back in a dark, dank cavern. It is here that it is properly studied and verified according that such rudimentary artifacts could be more to reasonable criteria. For a time, very early sites easily identified, provided that the archaeologist may prove easier to find in South America, for or geoarchaeologist can recognize lithics rather whatever paleoecological reasons. If that is indeed more problematical than those of a Paleoindian the case, the Old World model of discontinuous assemblage. In fact, the best clues are provided by settlement outlined here may at least allow skep- hearths, identifiable in sections by three possible tical archaeologists to examine such sites on their criteria: dark lenses with organic enrichment or own merits, rather than to insist a priori that carbonization; ash lenses or laminae, often but there be counterparts everywhere else. If such not necessarily white; and reddish, baked, or oxi- sites do stand up to closer examination, then it dized laminae (Butzer, 1982:82-85). Combina- would only be a matter of time before a radical tions of such thin-bedded strata obviously need restructuring of research strategies would repli- closer examination, by more rigorous criteria, to cate such records in certain other areas. confirm their identification, but they offer the ea- siest features to spot and examine. I am deeply grateful to Nihde Guidon (Paria) for providing The risk-minimization model and the South access to her unpublished data from Pedra Furada, and to Michael Collins (Austin) for allowing me to examine the ma- American site examples imply that prePaleo- teriale from Monte Verde. A preliminary draft of the manu- indian sites will neither be simple to locate nor Beript profited from thoughtful comments by Thomas Volman numerous, and this brief sketch for a geoarchaeo- (Cornell), by Richard Klein (Chicago), and Michael Collins. logical strategy illustrates why such sites will although I aasume full responsibility for the inferences made have limited visibility and have not yet been and conclusions drawn. documented in the United States. Martin (1987), in arguing that a “pre-Clovis”record, if it exists, should have been as conspicuous as the (Upper) REFERENCES Paleolithic of Japan, exhibits serious miscon- Adovasio, J.M.,and Carlisle, R.C. (1988). The Meadowcroft ceptions of Old World . The “Middle” Rockshelter. Science 298, 713-714. Paleolithic of East Asia is a more appropriate ref- Aikens, C.M., and Higuchi, T. (1982). 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