The Dragons of Eden: Speculations on the Evolution of Human Intelligence is a Pulitzer Prize-winning[1] 1977 book by Carl Sagan. In it, Sagan combines the fields of anthropology, evolutionary biology, psychology, and computer science to give a perspective on how human intelligence may have evolved.
Sagan discusses the search for a quantitative means of measuring intelligence. He argues that the brain to body mass ratio is an extremely good correlative indicator for intelligence, with humans having the highest ratio and dolphins the second highest,[2] though he views the trend as breaking down at smaller scales, with some small animals (ants in particular) placing disproportionally high on the list. Other topics mentioned include the evolution of the brain (with emphasis on the function of the neocortex in humans), the evolutionary purpose of sleep and dreams, demonstration of sign language abilities by chimps and the purpose of mankind's innate fears and myths. The title "The Dragons of Eden" is borrowed from the notion that man's early struggle for survival in the face of predators, and in particular a fear of reptiles, may have led to cultural beliefs and myths about dragons.
https://en.wikipedia.org/wiki/The_Dragons_of_Eden