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genes in humans, although some specific genes seem to have undergone positive selection.

This pattern of loss of function of olfactory genes is related to the reduced area of olfactory epithelium and relatively small olfactory bulb in humans. Likely enough, the development of cooking and the use of cultural traditions to identify suitable food items reduced our dependence on olfaction. The beginning of cooking likely also caused major changes in human diets which should be reflected in the genome (Wrangham, 2009). Our Australopithecine ancestors were probably largely herbivorous. Early species of Homo were probably generalist omnivores with significant access to hunted and scavenged fat and meat (Ungar et al., 2006). By Middle and Upper Paleolithic times, stable isotope analysis and zooarchaeological remains suggest that humans were highly carnivorous (Stiner, 1992; Richards et al., 2001). The expansion of brains in Homo was very likely tied to improved nutrition via hunting and cooking (Leonard et al., 2007). Genes associated with dietary changes and brain-size increase should be correlated to each other and to patterns derived from paleoanthropology.

Evolution of Language and Social Organization

Language and social organization were probably closely related in the course of human evolution. Much of our use of language is related to social life, and it is reasonable to assume considerable parallelism in their evolution (Dunbar, 1996). They are both features that fossilize poorly. Inferences about their presence or absence are not easy to make. For example, Philip Lieberman (2007) has long argued from anatomical evidence regarding the shape of the vocal tract that the capacity to clearly articulate modern vowel systems only emerged around 50 kya. He nevertheless thinks that ancient species of Homo had some useful capacity for speech. Indeed, there is perhaps a consensus among evolutionists writing on language that it evolved by culture-led gene–culture coevolution over an extended portion of our evolutionary history (Richerson and Boyd, in press). Nevertheless, dissenters on this point certainly exist. For example, Tattersall (2007) argues that articulate language must have originated only 50 kya. He cites not only the anatomical evidence but also the late first finds of unambiguous symbolic artifacts such as art. Those who imagine that language arose by prolonged culture-led coevolution differ greatly in the details of their scenarios. For example, Pinker (2003) argues that coevolution will lead to complex innate cognitive specializations for language. Kirby et al. (2007) use simulations to illustrate how the basic features of language might be cultural adaptations to preexisting cognitive constraints on language learning. That is, language evolved to fit our brain,



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