By focusing on human cognitive capabilities, Vaesen dismisses the function of the group dynamic in the emergence of complex social repertories (Garrod & Doherty Reference Garrod and Doherty1994; Steels Reference Steels2006; Steels et al. Reference Steels, Kaplan, Mcintyre, Van Looveren and Wray2002). Underlying biological capacities tend to be difficult to delineate; the same biology often displays considerable behavioral flexibility in response to shifts in social dynamics and environmental challenges. Vaesen's nine cognitive prerequisites are important for human cultural evolution, but one can make only educated guesses about how, why, or when these capabilities emerged. Evidence for cognitive capacities is inferred from the presence of the tool assemblages they purport to explain, without independent evidence for the direction of causation. Certainly, one can argue that many if not all of these capacities, including language, were present in Homo erectus toolmakers.

Three parameters are consistently associated with complex cultural adaptations to an environment: (1) relatively large brains and prolonged postnatal, activity-dependent maturation of the central nervous system, (2) environmental stress, and (3) increased population densities. Over hominin evolution, as a consequence of maturational delays and encephalization, human brains came to have remarkable developmental plasticity throughout the lifespan. Changes in life history created the potential for behavioral flexibility and altered social dynamics among mothers, infants, and others (Hrdy Reference Hrdy2009; Kaplan et al. Reference Kaplan, Hill, Lancaster and Hurtado2000; O'Connell et al. Reference O'Connell, Hawkes, Blurton Jones, Ungar and Teaford2002; Ragir Reference Ragir1985). Evidence for maturational changes is abundant in the fossil record beginning 3–4 mya and indicates a relatively modern profile of prolonged juvenile growth and encephalization beginning with H. erectus (Ragir Reference Ragir2000). The altered human life history is best explained through changes in habitat, diet, and locomotion (Aiello & Wells Reference Aiello and Wells2002; Cachel & Harris Reference Cachel, Harris, Bower and Sartono1995; Laden & Wrangham Reference Laden and Wrangham2005; Ragir et al. Reference Ragir, Rosenberg and Tierno2000). The transition from Acheulean to Middle Palaeolithic in Europe (Middle Stone Age in Africa) took place long after the appearance of a human-size brain and developmental profile. This leaves the interdependence between environmental stress and regional population growth as the incentive for the proliferation of human technologies in the Middle Pliestocene.

Improvements in diet supported increases in population densities by decreasing birth spacing (Aiello & Key Reference Aiello and Key2002). Intensification of exploitation of local resources has been closely associated with a division of labor and the specialization of knowledge required for rapid technological advancement (Jochim Reference Jochim1981). Technological advancement progresses slowly where populations are small and widely dispersed, and where there is little external pressure for change, as in modern hunter-gatherer societies (Jochim Reference Jochim1976); indeed, technological advances may be lost between generations when there is a drop in population density (Boserup Reference Boserup1981).

Let us consider how changes in population density result in the specialization of labor and knowledge using cooking as an example. Within a community, cooking skills are typically widespread, but the quality of production is uneven. In small communities, foods are often limited to local produce and ethnic tradition, and equipment is general purpose. Among home cooks, some are especially talented and capable of producing high-quality meals, but their innovative recipes and techniques often disappear after a generation or two. As communities increase in size, functional institutions appear (e.g., courts, estates, the army) that use full-time cooks to prepare meals for dozens of people. Professionals design specific tools to take the guesswork out of combining ingredients and systematize the techniques and timing of food preparation. With specialization comes a formal transfer of skills in the form of recipes, apprenticeships, and schools that disseminate a standardized knowledge of cooking methods. Archaeologically, the simple artifacts of home cooking appear as early as sedentary villages; and these continue to be found even after the appearance of the specialized toolkits of professional chefs. One does not supersede the other – they continue, one changing slowly and the other proliferating innovations, spatially but not temporally distinct.

Studies of language formation offer further insights into the emergence of complex cultural repertories. Among deaf individuals, the effect of community size on the emergence of communication systems from home sign to fully developed sign languages demonstrates the centrality of social dynamics. Isolated deaf children invariably use gestures to communicate with family members and achieve a perceptible degree of systematization in their gestural repertories (Goldin-Meadow Reference Goldin-Meadow2003). However, within a broader community, systemization creates stable, broadly shared system of signs (Kendon Reference Kendon1984). Given a community open to new learners, the informal syntax of a pidgin coalesces into a formal syntactic system within a few generations (Kegl et al. Reference Kegl, Senghas and Coppola1999). Whereas isolated deaf children create idiosyncratic conventions in interaction with their families, global conventions emerge only within communities of some critical size (Ragir Reference Ragir and Wray2002; Senghas et al. Reference Senghas, Senghas, Pyers, Langer, Parker and Milbrath2005).

Simulations and experimental studies further demonstrate the role of collaborative learning in the proliferation and maintenance of novel systems of information exchange. Fay, Garrod, and colleagues (e.g., Fay et al. Reference Fay, Garrod, Roberts and Swoboda2010; Garrod et al. Reference Garrod, Fay, Rogers, Walker and Swoboda2010) compared the emergent graphic communicative systems of those participants engaged in pair-wise interactions with different group members and those of isolated pairs over an equivalent number of communicative turns. Only in the case of community-wide interactions did individuals converge on a global system. Furthermore, global signs were found to be more transparent with respect to meaning than were those produced by isolated pairs (Fay et al. Reference Fay, Garrod and Roberts2008). These results suggest that system standardization and streamlining may require collaborative negotiations among members of groups larger than a family (Fay et al. Reference Fay, Garrod and Carletta2000).

Group dynamics lead to the emergence of conventional procedures and global symbols, in such domains as ceramics, fashion, music, and the Internet, from cottage crafts to the assembly line. The resultant technologies alter the ontogeny of individual minds, in the form of activity-dependent changes in information processing (Bavelier et al. Reference Bavelier, Green and Dye2010; Donald Reference Donald1991; Greenfield Reference Greenfield1984; Tobach et al. Reference Tobach, Falmagne, Parlee, Martin and Scribner Kapelman1997). Simple negotiations of information are capable of producing unexpectedly complex behavioral repertories, such as seen among social insects, migratory birds, and animals engaged in cooperative parenting (Hrdy Reference Hrdy2009). Social interactions that systematize activities and negotiate global conventions effect significant changes in neural connectivity and cognitive functions. Unique human faculties are likely to emerge as the result of, rather than as necessary conditions for, innovative cultural repertories.