Canoes and Cultural Evolution
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COMMENTARY Canoes and cultural evolution Stephen Shennan* Institute of Archaeology, University College London, London WC1H 0PY, United Kingdom ver the last 30 years, the idea the way in which cultural entities and cultural traits that characterize agricul- that the processes producing processes closely match Darwin’s origi- ture spread and, in some cases, subse- cultural stability and change nal formulation of the theory of evolu- quently influenced genetic evolution are analogous in important tion has recently been shown in detail [e.g., the ability to digest lactose (6)]. Orespects to those of biological evolution by Mesoudi et al. (5)]. In the most gen- An analogous process of cultural selec- has become increasingly popular. Bio- eral terms, parallel mechanisms for in- tion can also operate if individuals with logical evolution is characterized by heritance, mutation, selection, and drift certain cultural traits are more likely to changing frequencies of genes in popula- act on culture as they do on genes. be taken as models for imitation than tions through time as a result of such In the case of culture, the inheritance others, by virtue of those traits, and processes as natural selection; likewise, mechanism is social learning: People these individuals in turn become suc- cultural evolution refers to the changing learn ways to think and act from others. cessful models as a result. The traits distributions of cultural attributes in Of course, the routes through which cul- concerned will become more prevalent populations, which are affected by pro- ture is inherited are much more diverse even if they have no bearing on repro- cesses such as natural selection but also than those for genes (1), and different ductive success whatsoever and, indeed, by others that have no analogue in ge- routes have different consequences for even if they are deleterious to it, be- netic evolution. The fundamental, math- cause if a trait is passed on in a manner ematically based theory that justified other than by parents to children, there and spelled out the necessary modifica- Natural selection can is no reason for its success to depend on tions to standard population genetics the reproductive success of the individu- theory to make it relevant to culture also act on cultural als concerned. For example, if celibate was laid out by Cavalli-Sforza and Feld- priests are more likely to be influential man (1) and Boyd and Richerson (2) in attributes. teachers than other adults and if, as a the 1980s, on the basis of earlier papers, result of what they teach, their pupils and Richard Dawkins (3) had already are more likely to be celibate priests and introduced the idea to the popular imag- the patterning of cultural change teachers, then the values they teach will ination with his concept of the ‘‘meme’’ through time. Variation in what is inher- increase in frequency in the population. as analogous to the gene. In the inter- ited is generated by innovations. These However, in addition to these selec- vening period, the development of what innovations may be unintended copying tion mechanisms, a number of ‘‘bias’’ has come to be called ‘‘dual inheritance errors, but they can also be intentional processes can affect what is transmitted; theory’’ or ‘‘gene–culture coevolution changes, perhaps arising from trial-and- these bias processes are factors that af- theory’’ has continued, and it has been error experimentation, which lead an fect what and who people try to copy accompanied by a slowly growing num- individual to stop performing a task the when they are learning from others. ber of empirical case studies that apply way he had previously learned and to Thus, ‘‘results bias’’ refers to the situa- these ideas to understanding patterned start doing it differently, or even to do tion in which people look at what other variation in cultural data. The article by people do (for example, the crops they Rogers and Ehrlich (4) in this issue of something different altogether. Whether plant), compare the results with what PNAS makes a significant contribution this novelty will be widely adopted de- they are doing themselves, and then to this growing field by showing how pends on a range of selection and bias different cultural evolutionary processes mechanisms, many of which have no change what they do because the other can be identified and distinguished from equivalent in genetic evolution but way of doing things seems to be more one another and how they differentially whose existence and importance have effective. ‘‘Content biases’’ are affected affect different kinds of cultural traits; it formed the subject of major develop- by features of transmissible phenomena will certainly become a widely cited ments in cultural-evolution theory over that make them intrinsically more or classic case study, and the dataset of the last 30 years (especially refs. 1 and less memorable for reasons relating to descriptive traits of canoes from differ- 2). It is important to spell out these the structure of the mind or the strong ent Polynesian groups is likely to be- mechanisms. reactions they provoke; examples may come a test bed for future cultural evo- Natural selection in the narrowest include be fairy tales or so-called urban lutionary studies. sense affects humans as it does members myths. ‘‘Context biases’’ are aspects of of all other species. However, as Rogers the context of learning that affect what The Processes of Cultural Evolution and Ehrlich (4) describe, natural selec- is transmitted; thus, something may be Of course, the idea that human culture tion can also act on cultural attributes, copied simply because the person ini- might usefully be approached by using in the sense that those individuals who tially doing it is prestigious (‘‘prestige ideas from biological evolution is not a inherit or acquire certain cultural at- bias’’) or because it is what most people new one, as the quotation by the French tributes may have a greater probability do locally (‘‘conformist bias’’). In the source in 1908 cited by Rogers and Ehr- of surviving and/or reproducing than latter two cases, whether a particular lich (4) indicates, but it has had a check- those who do not; as a result, those cul- ered history. Only in the late 1970s did tural attributes will become increasingly this idea’s long period of unpopularity prevalent. For example, it is clear that, Author contributions: S.S. wrote the paper. begin to end. The extent to which cul- in many parts of the world, adopting an The author declares no conflict of interest. tural processes may be modeled in evo- agricultural rather than a hunting-and- See companion article on page 3416. lutionary terms remains disputed, as gathering way of life led to greater *E-mail: [email protected]. Rogers and Ehrlich point out [although reproductive success; as a result, the © 2008 by The National Academy of Sciences of the USA www.pnas.org͞cgi͞doi͞10.1073͞pnas.0800666105 PNAS ͉ March 4, 2008 ͉ vol. 105 ͉ no. 9 ͉ 3175–3176 Downloaded by guest on September 26, 2021 cultural attribute or practice becomes acting on the cultural lineages identified Rogers and Ehrlich (4) refer to the more prevalent in a population has is a lot harder. process acting on the functional canoe nothing to do with its intrinsic pro- traits as natural selection, and so it is perties but only with the context of Canoe Evolution from the perspective of the traits them- learning. What Rogers and Ehrlich (4) have done selves, in that particular traits survive Finally, there is the cultural equiva- is make progress in this area by showing and are copied preferentially as a result lent of genetic drift. In other words, the that variation that is believed to be un- of their greater functional effective- ness—something that could in principle der selection is patterned differently frequencies of particular cultural at- be tested experimentally. The results tell tributes can change for essentially from other variation that is believed not us that either there was a very low inno- chance reasons not involving any prefer- to be under selection, or at least not in vation rate or the vast majority of those ence for a particular attribute. Who or the same way. It seems to be more con- innovations that occurred were unsuc- what you copy may simply be a random servative and, therefore, under negative cessful and therefore short-lived. What choice dependent on who or what you selection. Perhaps more surprisingly, they do not do is distinguish between meet. they find that there is no correlation at natural selection operating on human all in the similarities between island agents via cultural traits, and thus on The “Meme’s Eye-View” groups in terms of functional canoe the future frequency of those traits, and As just described, all of these processes variation and the similarities based on results bias, as defined above. In other focus on the people involved in the pro- symbolic variation. One might have ex- words, the process could have operated cesses. This is obviously an extremely pected some correlation, either because as a result of the makers and users of important perspective, but it is not the both would be affected by the distance ineffective canoes drowning more fre- quently, thus leading to the demise of only one. It is also important to look at between the islands, or because the pro- those designs, whereas groups with bet- things from what Dawkins called ‘‘the cess of island colonization by groups in ter-designed canoes, perhaps different meme’s eye-view,’’ the perspective of canoes would have brought both their communities, survived and colonized the cultural attributes themselves.