Evolutionary Anthropology 123 ARTICLES The Evolution of Cultural Evolution JOSEPH HENRICH AND RICHARD McELREATH Humans are unique in their range of environments and in the nature and diversity of attempted to glean as much as they their behavioral adaptations. While a variety of local genetic adaptations exist within could from the aboriginals about nar- our species, it seems certain that the same basic genetic endowment produces arctic doo, an aquatic fern bearing spores foraging, tropical horticulture, and desert pastoralism, a constellation that represents they had observed the aboriginals us- a greater range of subsistence behavior than the rest of the Primate Order combined. ing to make bread. Despite traveling The behavioral adaptations that explain the immense success of our species are along a creek and receiving frequent cultural in the sense that they are transmitted among individuals by social learning and gifts of fish from the locals, they were have accumulated over generations. Understanding how and when such culturally unable to figure out how to catch evolved adaptations arise requires understanding of both the evolution of the psycho- them. Two months after departing logical mechanisms that underlie human social learning and the evolutionary (popu- from their base camp, the threesome lation) dynamics of cultural systems. had become entirely dependent on nardoo bread and occasional gifts of fish from the locals. Despite consum- In 1860, aiming to be the first Euro- three men (King, Wills and Gray) ing what seemed to be sufficient calo- peans to travel south to north across from their base camp in Cooper’s ries, all three became increasingly fa- Australia, Robert Burke led an ex- Creek in central Australia with five tigued and suffered from painful tremely well-equipped expedition of fully loaded camels (specially im- bowel movements. Burke and Wills ported) and one horse. Figuring a soon died, poisoned and starved from maximum round trip travel time of eating improperly processed nardoo three months, they carried twelve seeds. Unbeknown to these intrepid weeks of food and supplies. Eight adventurers, nardoo seeds are toxic Joseph Henrich received his Ph.D. in and highly indigestible if not properly 1999 from the University of California, Los weeks later they reached tidal swamps Angeles, and is currently Assistant Pro- on the northern coast and began their processed. The local aboriginals, of fessor of Anthropology at Emory University. return. After about ten weeks their course, possess specialized methods He was recently a fellow in the Society of Scholars at the University of Michigan and supplies ran short and they began eat- for detoxifying and processing these at the Institute for Advanced Study in Berlin. ing their pack animals. After twelve seeds. Fatigued and delusional, King He has conducted ethnographic and exper- wandered off into the desert where he imental research among the Machiguenga weeks in the bush, Gray died of illness of Peru and the Mapuche of southern Chile. and exhaustion, and the group jetti- was rescued by an aboriginal group, His theoretical work has involved construct- soned most of their remaining sup- the Yantruwanta. He recovered and ing formal models of the evolution of cul- tural learning capacities, cultural evolution, plies. A month later, they arrived back lived with the Yantruwanta for several and culture-gene coevolution. E-mail: in their base camp, but found that months until a search party found [email protected] their support crew had recently de- him. Richard McElreath received his Ph.D. in 2001 from the University of California, parted, leaving only limited supplies. The planning for this expedition Los Angeles, and is now Assistant Pro- Still weak, the threesome packed the could not have been more extensive, fessor of Anthropology at the University of California. He was recently a postdoc- available supplies and headed to the and these men were not unprepared toral fellow at the Center for Adaptive Be- nearest outpost of “civilization,” Mt. British schoolboys out on holiday. havior and Cognition, Max Planck Insti- Hopeless, 240km south. In less than a However, despite their big brains, tute for Human Development, Berlin. He conducts ongoing field work to investi- month, their clothing and boots were camels, specialized equipment, train- gate cultural microevolution among sev- beyond repair, their supplies were ing, and seven months of exposure to eral ethnic groups in southwest Tanzania. the desert environment prior to run- E-mail: [email protected] again gone, and they ate mostly camel meat. ning out of supplies, they failed to sur- Faced with living off the land, they vive in the Australian desert. This bit Key words: social learning; human evolution; culture began foraging efforts and tried, un- of history makes a simple point: Hu- and cognition; coevolution; dual inheritance theory successfully, to devise means to trap mans, unlike other animals, are birds and rats. They were impressed heavily reliant on social learning to Evolutionary Anthropology 12:123–135 (2003) by the bountiful bread and fish avail- acquire large and important portions DOI 10.1002/evan.10110 Published online in Wiley InterScience able in aboriginal camps, in contrast of their behavioral repertoire. No (www.interscience.wiley.com). to their own wretched condition. They evolved cognitive modules, “evoked 124 Evolutionary Anthropology ARTICLES culture,” or generalized cost-benefit things, how different modes of cul- Conceptualizing culture as socially calculators delivered to these men the tural inheritance affect rates and out- learned information stored in people’s knowledge of how to detoxify nardoo comes of cultural evolution2 and how brains opens up new sets of evolution- spores or how to make and use rat natural selection acting on genes can ary questions. We will review the re- traps, bird snares, or fishing nets from produce a semi-autonomous inheri- search on five of these: How does so- locally available materials. Unlike so- tance system.7 Like human behavioral cial learning in humans increase cial learning in other animals, human ecology,8 coevolutionary and dual-in- adaptability and thereby allow our cultural abilities generate adaptive heritance theories are concerned with species to successfully occupy such an strategies and bodies of knowledge adaptation. Unlike human behavioral enormous range of environments? If that accumulate over generations. ecology, however, these theories cultural learning mechanisms are so Foraging, as it is known ethnographi- model the proximate mechanisms adaptive, why are such mechanisms cally, would be impossible without that produce adaptations. Like evolu- seemingly rare in nature? What cog- technologies such as kayaks, blow- tionary psychology, these theories nitive processes guide human social guns, bone tools, boomerangs, and share an interest in the design of cog- learning? If cultural variants do not bows. These technological examples nition. Unlike most evolutionary psy- replicate like genes, can culture embody skills and know-how that no chology, however, dual-inheritance evolve? How does the coevolution of single individual could figure out in and gene-culture models are rigor- genes and culture influence human his lifetime. Nonmaterial culture, ously formalized, take account of so- psychology and the histories of hu- such as seed processing techniques, cial learning, and explore population man societies? These five questions tracking abilities, and medicinal plant processes. For many questions, build a natural progression of puzzles, knowledge, reveals similar locally strictly outcome-oriented or culture- from the genetic origins of cultural adaptive accumulations. Interest- free models are sufficient and insight- inheritance to the dynamics of mod- ingly, this adaptive information is of- ful. For many others, however, taking ern cultural and societal evolution. ten embodied in socially learned account of cultural dynamics is essen- rules, techniques, and heuristics that tial. As the Burke and Wills story illus- are applied with little or no under- trates, even hunter-gatherer adapta- WHY IS CULTURAL LEARNING standing of how or why they work. tion is substantially reliant upon ADAPTIVE? Thus, understanding a substantial evolved cultural knowledge and tech- To understand the evolution of so- amount of human adaptation requires nology. To understand adaptation in cial learning, theorists have developed understanding the cultural learning human societies with any time depth formal models to study how temporally processes that assemble our behav- seems very difficult without some at- and spatially changing environmen- ioral repertoires over generations. tempt to account for the evolutionary tal conditions affect the evolutionary This is not, however, a call to separate dynamics that produce such adapta- trade-offs between capacities for in- humans from the rest of nature. A tions. dividual learning (for example, trial productive approach should seat hu- Throughout this paper we will use and error), social learning, and “hard- mans within the broader context of “cultural learning” and “cultural wired” behavioral responses.1,5,7,9–15 mammalian and primate evolution transmission/acquisition” to refer to Most of these models are very abstract while at the same time being able to the subset of social learning capacities and apply to a wide range of animal explain how and why humans are so that allow for cumulative cultural evo- social learning, not just