Second, this collection of cognitive programs evolved in the Pleistocene to solve the adaptive problems regularly faced by our hunter-gatherer ancestors-...

Many of the most important properties of human groups – including properties that may give one group an evolutionary advantage over another – are properly defined only at the level of group organization. Yet at present, most work on the evolution of culture has focused solely on the transmission of individual-level traits. I propose a conceptual extension of the theory of cultural evolution, particularly related to the evolutionary competition between cultural groups. The key concept in this extension is the emergent (...) group-level trait. This type of trait is characterized by the structured organization of differentiated individuals and constitutes a unit of selection that is qualitatively different from selection on groups as defined by traditional multilevel selection theory. As a corollary, I argue that the traditional focus on cooperation as the defining feature of human societies has missed an essential feature of cooperative groups. Traditional models of cooperation assume that interacting with one cooperator is equivalent to interacting with any other. However, human groups involve differential roles, meaning that receiving aid from one individual is often preferred to receiving aid from another. In this target article, I discuss the emergence and evolution of group-level traits and the implications for the theory of cultural evolution, including ramifications for the evolution of human cooperation, technology, and cultural institutions, and for the equivalency of multilevel selection and inclusive fitness approaches. (shrink)

The Shape of Thought: How Mental Adaptations Evolve presents a road map for an evolutionary psychology of the twenty-first century. It brings together theory from biology and cognitive science to show how the brain can be composed of specialized adaptations, and yet also an organ of plasticity. Although mental adaptations have typically been seen as monolithic, hard-wired components frozen in the evolutionary past, The Shape of Thought presents a new view of mental adaptations as diverse and variable, with distinct functions (...) and evolutionary histories that shape how they develop, what information they use, and what they do with that information. The book describes how advances in evolutionary developmental biology can be applied to the brain by focusing on the design of the developmental systems that build it. Crucially, developmental systems can be plastic, designed by the process of natural selection to build adaptive phenotypes using the rich information available in our social and physical environments. This approach bridges the long-standing divide between "nativist" approaches to development, based on innateness, and "empiricist" approaches, based on learning. It shows how a view of humans as a flexible, culturally-dependent species is compatible with a complexly specialized brain, and how the nature of our flexibility can be better understood by confronting the evolved design of the organ on which that flexibility depends. (shrink)