Why don’t humans have as much hair as other primates?
From Lisa Preston.
Humans evolved from apes, so our earliest human-like ancestors, known as hominins, were ape-like in appearance. Around 3 million years ago, it is thought that these early hominins would have been covered in fur, but between 2–3 million years ago they started to inhabit open savannahs where they were exposed to the glare of the Sun. They also started to hunt large animals, which required running over long distances. A hairy coat would have kept the hominins too warm for this new lifestyle, so it is thought that they gradually evolved to have less hair in order to keep cool.
Answered by Joanna Stass for Brain Dump in How It Works issue 107