The Collective Brain

Long before the origins of agriculture or the rise of the first cities, our species spread out across the globe into an immense diversity of environments, from the frozen tundra of Siberia to the arid deserts of Australia. Our species’ immense ecological success in these environments depended not on our vaulted intelligence or rationality, or on any array of local genetic adaptations as in other species. Instead, human survival and success depends on the inheritance of large bodies of culturally-transmitted information that accumulates and aggregates over generations to produce cultural adaptations. Our species’ degree of reliance on cultural learning means that a population’s ability to generate and maintain complex cultural repertoires, tools and technologies, such as those commonly found among hunter-gatherers, depends on its sociality, and specifically on its social norms and institutions. Thus, our apparent intelligence derives more from our collective brains than our individual intelligence. Overall, the emergence of this second system of inheritance sparked a culture-gene coevolutionary duet that has driven genetic change in our species for over a million years. Many aspects of our anatomy, physiology and psychology, from our big brains to our short colons, only make sense in the light of culture-gene coevolution.