Recent Critiques of Dual Inheritance Theory

ESIC 2017 Recent Critiques of Dual Inheritance Theory Peter J. Richerson Abstract e dual inheritance or gene–culture coevolution theory of human evolution was developed in the 1970s and 80s. Early work built mathematical theories derived from then- current work in human development, sociolinguistics, and the diusion of innovations. More recently it has included a considerable amount of new empirical work. e theory has always had critics in evolutionary biology and the social and behavioral sciences. Morin’s book critiques the theory from an alternate epidemiological or attraction theory of cultural evolution that doubts that imitation and adaptation play signicant roles in cultural evolution. Lewens book is a wide-ranging analysis of critiques of gene–culture coevolution theory that nds most of them in error or at least not fatal to the project. His book includes a chapter on critiques based on considerations of human nature, of which Morin’s book is one variant, and which Lewens argues are faulty. at is also my conclusion. Keywords: cultural evolution, dual inheritance theory, attraction theory, human nature BOOKS UNDER REVIEW the inaccuracy of the transmission process. The Flop Problem is that no matter how faithfully Lewens, Tim. 2015. Cultural Evolution: Conceptual Challeng- we perform some microtradition, most such es . New York: Oxford University Press. Hardcover $45.00; performances will be unobserved or ignored by Kindle $17.04. others, ending its propagation. Morin argues Morin, Olivier. 2016. How Traditions Live and Die . New York: that solving the Flop Problem solves the Wear Oxford University Press. Hardcover $99.00; paperback $39.95; Kindle $15.65. and Tear Problem, but he claims that many authors seem to think that the reverse is true. HOW TRADITIONS LIVE AND DIE He disparages the idea that speedy, accurate imitation and teaching, which might reduce Morin’s big questions for his How Traditions the Wear and Tear Problem, play any significant Live and Die (hereafter HTLD) are “Why is role in cultural transmission. He argues that the there culture instead of nothing?” And “Why real work is done by ostensive communication among humans rather than elsewhere?” Some by which he means communication that points cultural traditions are quite long-lived, but to something, say, to convey the meaning of many are not. His basic argument is that for a word by pointing to an example. He asserts cultural traditions to persist a tradition must that this is a soft form of inheritance in which solve what he calls the “Flop Problem” and the the recipient of the communication must do “Wear and Tear Problem.” The Wear and Tear substantial reconstructive work to acquire the Problem is manifest in the game of Chinese cultural item in question. The only way that a Whispers, in which a simple story is told by one cultural tradition can persist for very long is for person to another and by the second person to two conditions to obtain. First, learners must a third and so on down the line. Such a micro- exist in a thick network of communication such tradition is rapidly corrupted, worn and torn by that they are exposed repeatedly to the same Peter J. Richerson idea. Narrow communication chains are bound Sperber (1996). In this theory, one of the to flop. Second, a successful tradition must main causes of attraction is universal, evolved somehow be attractive to persist. HTLD pic- cognitive biases. Indeed, in HTLD this seems tures human history as a slow accumulation of to be the most consequential type of attractor. traditions that are sufficiently attractive to per- Of course, proponents of this theory readily sist for a long period of time. At the same time admit that all sorts of local considerations also he disparages the idea that human history often shape culture, the idiosyncratic evolution of involves the relatively gradual increase in the the vocabulary and grammar of particular lan- sophistication of technology and social organi- guages is an example given in HTLD. Sound zation, what many of us refer to as cumulative symbolism, the tendency of words in many lan- cultural evolution. He instead sees the accumu- guages to use similar-sounding words to express lation of traditions as just more relatively simple similar ideas, is given as an example of a univer- traditions. sal cognitive attractor. HTLD ends with a “strange vision: There I think that the importance of universal cog- could have been human populations just like we nitive attractors of the kind Morin refers to is know them, with humans communicating and greatly exaggerated. In dual inheritance theory, cooperating just like we do, but whose cultural the local differences in cultures are largely what traditions resemble those of modern chimpan- are adaptive (Boyd and Richerson 1985). In zees” (11, 213–52). Intrinsic attractors shape theory, culture is a very good system for adapt- cultural traditions, but the essential adaptations ing to environmental variation in time and for communicating and cooperating derive space. In particular, it is good for adapting to from human nature. Traditions are just an acci- environments that vary on shorter time or space dental by-product of our communicating. scales that natural selection on genes can easily I had a strange vision once myself when track. Because, on the human scale, it apparently I was eleven or twelve. I imagined the wind requires a very large and costly brain, culture has blew because trees waved their branches; even to more than pay this high overhead cost. the grass blades did their brave little best to How do cultural traditions lead to local help. Since wind blowing and branch waving adaptations? Take diet as an example. Our clos- are highly correlated, I didn’t see any way of est living relatives rely disproportionately on disproving this hypothesis with the information fruit and have a limited repertoire of cultural I had at hand, though all the adults I mentioned tricks, such as termite fishing, to extract pro- it to found it strange. Subsequently, I learned tected resources. Humans are heavily reliant in high school biology that plants don’t have on tool-based extraction, hunting and farming the analogue of muscles. In university biology for their subsistence. This leads to traditional I learned that this is because photosynthesis knowledge of the natural history of local areas generates too little energy to make such activ- and specialized toolkits adapted to hunt and ities possible. Not until after graduate school extract the resources of these places. Compare did I understand enough atmospheric science two marine-focused traditions, that of the to understand what really drives the wind. Inuit and that of the Polynesians. The water- Is Morin’s notion of nonadaptive culture and craft they deploy are very different but elegantly the importance of human nature as dubious as my adapted to their environments. The Polynesian waving branches theory of the wind? I think so! outrigger canoe is fast and allows foraging The chief reason that Morin thinks that over a wide area. But it capsizes rather easily, culture is an accidental by-product is that he a modest handicap because being dunked in a subscribes to the attractor or epidemiological tropical sea is not particularly dangerous. The theory of cultural change proposed by Dan skin-covered kayak of the Inuit makes use of 204 Evolutionary Studies in Imaginative Culture Recent Critiques of Dual Inheritance Theory only a small amount of scavenged driftwood Polynesians and the Inuit. Farming systems and, if capsized, can be quickly flipped upright were developed to adapt to semideserts and before its operator gets wet in fatally cold water. oases, poor tropical soils, and the extreme eleva- The Polynesian diet is mostly cultivated crops tions of the Andes and the Himalaya. Reindeer for calories supplemented by fish for protein. herders practice a form of pastoralism north The Inuit traditionally had almost no access to of the Arctic Circle. Twentieth-century eco- plant foods and relied on eating raw meat to logical anthropologists have given us excellent obtain vitamin C. The Polynesians could afford accounts of many of these adaptations (e.g., to be rather casual about shelters and clothing, Steward and Faron 1959). Second, beginning whereas clever clothing and well- constructed around 5,000 years ago, some human societies shelters were life and death matters for the became dense enough to urbanize, and urban Inuit. Typhoons and droughts were serious communities began to elaborate a series of full- natural hazards in much of Polynesia, against time specialized roles—political elites, priests, which supplies of long-lasting fermented bread- potters, carpenters, brick-makers, jewelers, fruit are stored under the supervision of chiefs. merchants, and the like. In the last few centu- Archaeologists tell us that the Polynesian ries the size and internal complexity of many and Inuit adaptations evolved over considerable societies has exploded. Not all of these changes spans of time, some within the last few hun- may be sustainable in the long run, but they dred years. We know that we cannot depend have all seemed desirable to their innovators on human nature to supply us with some and adopters at the time. species-wide ur-knowledge because stranded By what evolutionary mechanisms do explorers and unsupported colonists often such cultural adaptations arise? First, people perish in environments where the well-adapted innovate by accident or design. New forms natives make a good living. If they are lucky, the of familiar tools and techniques appear. Then natives pass along enough of their traditional we seem to use a hierarchy of decision rules to knowledge to carry them over until resupply acquire or discard innovations we are exposed or rescue.

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