This three-part series, Becoming Human, on PBS’s Nova covers new theories about how and why we evolved into human beings and is well worth watching. You can watch all of the episodes here, as well as view several interesting mini-programs about related topics. This post covers the major idea presented in episode 2, “The Birth of Humanity.” It’s a doozy.
2) Sweating made us human. Okay, bear with me. The big brains we got from climate change needed more food to operate. Our brains use more energy and food than any other organ in our body. To get more food, we turned to meat, which is loaded in calories, protein, and fat. To get meat, since humans don’t have claws, fangs, or great strength, we had to figure out a new way get our meat fix. Scientists now think we turned to persistence hunting, which is chasing the prey until it collapses from exhaustion and then killing it. The Bushmen of Africa still do this, chasing antelopes and other game for several hours in the heat of the day, when most animals are sleeping. It turns out that humans are unique in this capability; we can run for hours in the hottest temperatures because we traded fur for sweating. They think that losing our body hair or fur and gaining the ability to sweat happened at the same time as our brains started to get bigger. Most animals cool themselves by panting. Humans can sweat over their entire bodies which is a more effective method for cooling. Our bigger brains triggered a number of adaptations to support that growth. Because our brains got bigger, we started eating meat, lost our body hair, started sweating, and were able to run down prey for hours at a time. Oh, and our big brains and our new appetite for meat caused us to develop stone tool-making to “process” our kills and fire-making to cook the meat to make it more easily digestible. But the ability to sweat was the big change that enabled everything else. Cool.