How there got to be so many of Us: The evolutionary story of population growth and a life history of cooperation

Abstract

One of the defining features of human evolution is our demographic success. As of August 2019, the world’s population exceeds 7.7 billion. The human capacity for population growth has profound effects on people’s lives today, but it is also one of the remarkable stories of our evolutionary past. Although most research and public attention has centered on the past 200 years, when growth has increased exponentially, global population growth prior to that was not trifling. Before the industrial era, humans populated all of the world’s environments with more than a billion people. Importantly, it was deep in the past when the biological and social underpinnings were established that allow humans to excel as reproducers and survivors. The evolutionary trends in fertility and survival that gave rise to human demographic success were fundamentally shaped by our ability to cooperate. This essay focuses on how the human dietary niche and life history presented novel opportunities for cooperation that tied younger and older generations together in ways that gave us our demographic edge.