The Evolution of Walking and Running
All animals need to be physically active, but the human lineage clearly underwent selection to be considerably more physically active than our relatively inactive ape ancestors and cousins including chimpanzees and gorillas. This selection likely occurred in at least two stages, first involving the most fundamental type of moderate physical activity, walking, and then the most fundamental type of vigorous physical activity, running. In terms of walking, the earliest hominins were likely selected to become bipedal in order to help them efficiently walk longer distances to forage. Bipedal walking brought many benefits and led to further selection for making and using tools, but also rendered hominins slow and awkward, hence vulnerable to predation. With the origins of hunting and gathering in the genus Homo, however, there was additional selection for endurance running which helped hominins become scavengers and hunters. Until recently, hunter-gatherers engaged in several hours a day of moderate physical activity from walking 9-15 km per day, as well as regular vigorous physical activity from occasional long-distance running. Industrial and post-industrial innovations, however, have changed how much and the ways we walk and run, and they enable humans to no longer have to engage in much physical activity. Today we face a growing epidemic of physical inactivity that increases people’s vulnerability to a wide range of chronic non-infectious diseases as well as infectious diseases including Covid-19.