EHAP Lecture Series: “The High Costs of Human Brain Development: Implications for the Evolution of Human Childhood”

Childhood – the period of prolonged and slow growth that follows weaning – is a unique evolutionary quirk of the human lifecycle. Current explanations for the evolution of childhood point to the reproductive advantages to the mother of weaning offspring earlier, which reduces energy demands while also allowing a shorter interbirth interval that increases completed fertility. Less well understood is why humans grow so slowly during childhood, when our offspring grow at a rate more typical of cold-blooded reptiles than of mammals. In this talk, Biological Anthropologist Christopher Kuzawa will present results from a new study that uses brain imaging to quantify the energetic costs of human brain development. These new findings show that the human brain consumes as much as 2/3rds of the body’s resting metabolism during infancy and childhood. The ages of most intensive brain energy use correspond closely with periods of slowest body growth, suggesting that slow body growth may have evolved to free up energy for the unusually high energy costs of developing the human brain. These findings provide new insights into the role of human brain energetics in the evolution of some of the unique features of the human lifecycle.