Sterelny’s Theory of Human Cognitive Evolution

A theory of human cognitive evolution needs to integrate the biological and social-scientific perspectives on human nature. Niche construction and its partial transformation into bona fide inheritance is the key to this integration. Some of the apparatus of hominid social life has become part of inherited hominid developmental resources. Hominids do not just inherit genes: they inherit epistemic resources that scaffold the development of life skills that are characteristic of their parents and of their immediate group, and which quite often distinguish them phenotypically from other hominids. Thus niche construction is a mechanism that supports developmental flexibility: a child becomes a skilled hunter rather than a fisherman because he inherits this set of developmental resources. Human genes have become adapted to sharing the job of directing development with an array of other resources. Moreover, since these new developmental resources are made and incorporated into inheritance systems more quickly than new genetic resources, one effect os a potential acceleration of hominid evolution. Expanded inheritance can then act as a means both for the evolutionary fragmentation of hominid lineages and as a means by which evolutionary change is accelerated.

Early in hominid evolution, it’s very likely that biological inheritance was much as it now is in chimps. To a reasonable approximation, a chimp inherits only genes from its parents. Though social learning is important in chimp life, and there is some meme-like flow of information from mothers to children, that flow is diffuse and short-lived. There is no evidence of deep behavioral traditions in chimp life, nor of cumulative downstream niche construction. There is no sign that group selection is allowing cooperation to take off. There are certainly some limited forms of cooperation: males cooperate to defend territory against other groups of chimps, to hunt, and to form coalitions against other males. Females too form coalitions. But there is little evidence of effective suppression of free-riding and defection. In contrast, over time in hominid evolution:

  1. Group selection became very important, and underwrote the evolution of a cooperation explosion, the effects of which include language, division of labor, and resource sharing.
  2. Cooperation itself accentuates niche construction: it becomes more powerful; more downstream, and more like genetic inheritance.
  3. As this transformation proceeds, elements of culture become elements of biology, as they become part of a developmental matrix which is transmitted from one generation to the next.
  4. Once information transmission became reliable and precise, downstream niche construction became cumulative, and Tomasello’s Ratchet began to work. That Ratchet required both cognitive and social preconditions, but once these were met, the Ratchet began to turn. Different human groups became more markedly differentiated, for their phenotypes come to reflect not just their current environmental differences but also the differences in their lineages’ learning history.
  5. The geographic expansion of the hominid range, the cumulative transformation of hominid lifeways, and the intensification of climatic variability select for flexible response.

Kim Sterelny, Thought in a Hostile World, p. 171-172

August 22, 2023