“Stand up straight! And do something about that hair!” Annoying? Sure. But such parental advice may have made humans what we are today. Because our upright stance, and relative lack of hair, may have enabled our human ancestors to run far and fast enough to capture their prey. So say scientists in the Journal of Human Evolution. [Graeme D. Ruxton and David M Wilkinson, "Thermoregulation and endurance running in extinct hominins: Wheeler’s models revisited"]
The idea that standing on two legs and shedding all that body hair might have helped early humans keep cool on the African savanna was first trotted out in the late 1980s. But those early models had our ancestors standing still in a gentle breeze. Scientists simply didn’t have the computational power to assess what might happen when those early humans had to up and chase down a meal.
The new model takes into account how hot a human would get running long and hard enough to outlast an animal galloping in the midday sun. And it shows that a hominin would have to have been as energetically efficient, and as hairless and sweaty, as we are today to avoid overheating. Homo erectus could probably have gone the distance, the scientists say. But Australopithicus probably didn’t have the legs.
[The above text is a transcript of this podcast.]