Chapter 26: Cultural and Social Evolution in Humans

Behavior is examined through the lens of instincts (innate, complex behaviors often under genetic control, such as honeybee communication) and learned behavior. Genetic components influence learned behaviors, demonstrated by genes affecting traits like tameness in dogs or social interaction deficits in mice lacking the disheveled gene. Learned behavior, which can be modified through individual or social experience, is highly responsive to environmental changes, exemplified by the sophisticated tool use observed in chimpanzees (e.g., complex termite fishing and nut cracking, often learned by imitation from mothers) and the manufactured tools of New Caledonian crows. Human cultural evolution, enabled by our intelligence, mental capacity, and rapid, conscious acquisition and transmission of practices via language and teaching, has vastly outpaced phenotypic evolution over time. Unlike genetic transmission, cultural change is not restricted to vertical transfer (parent to offspring) but can spread horizontally through interactions between related and unrelated individuals. The physical basis for this rapid change is linked to the distinctive nature of the human brain, which is significantly larger than those of our primate relatives, especially in the cerebral cortex and prefrontal cortex, areas associated with complex mental processing, although brain size itself has not changed over the last 100,000 years. Historically, the application of evolutionary principles to society led to Social Darwinism, a concept championed by figures like Herbert Spencer, which wrongly claimed that natural selection governed social organization and justified class structures and economic inequities based on the "survival of the fittest". This view is criticized because man-made laws, not biological ones, govern social goals. Seeking a more rigorous understanding of the biological underpinnings of social actions, the field of sociobiology emerged, defined as the systematic study of the biological basis of all social behavior, examining how genetic factors and environment interact to shape social traits, including difficult-to-explain behaviors like altruism.