The Evolution of Intelligence

How did the human species evolve the capacity not just to communicate complex ideas to one another but to hold such conversations from across the globe, using remote devices constructed from substances that do not exist in the natural world, the raw materials for which may have been hauled up from the bowels of the earth? How did we come to be so intelligent? Research at the interface of psychology, biology, anthropology, archaeology, and cognitive science is culminating in an increasingly sophisticated understanding of how human intelligence evolved. Studies of the brains of living humans and great apes and the intellectual abilities they support are enabling us to assess what is unique about human intelligence and what we share with our primate relatives. Examining the habitats and skeletons of our ancestors gives cues as to environmental, social, and anatomical factors that both constrain and enable the evolution of human intelligence. Relics of the past also have much to tell us about the thoughts, beliefs, and abilities of the individuals who invented and used them. The chapter starts with an introduction to some key issues in the evolution of intelligence. We then consider what is unique about human intelligence compared to our closest living biological relatives, the great apes – chimpanzees, bonobos, gorillas, and orangutans. The process by which the human intelligence came about is the next topic. Finally, we address the question of why human intelligence evolved – did it evolve purely due to biological forces, that is, does intelligence merely help us solve survival problems and attract mates, or are nonbiological factors such as culture involved? Key Issues We begin by laying out some of the fundamental issues that arise in considerations of the evolution of human intelligence. First, we address some issues of definition. Second, we comment on challenges to the accurate assessment of intelligence, particularly when comparing intelligence across different species. A third, related issue is the question of the extent to which there are special qualities of intelligence that only humans attain. Many methods are used to assess intelligence and its evolution. These include (1) behavioral measures, which may involve naturalistic observation or analyzing responses in laboratory experiments, (2); artifactual measures, which involve analysis of tools, art, and so forth,; and (3) anatomical/neurological measures, which involve studies of the brain and cranium. Ideally, all three would converge upon a unified picture of how intelligence evolved. However, …