Scientists have shown that human skulls changed in ways that indicate a lowering of testosterone levels at around the same time that culture was blossoming. Heavy brows were out, rounder heads were in. Technological innovation, making art and rapid cultural exchange probably came at the same time that we developed a more cooperative temperament by dialing back aggression with lower testosterone levels.
A composite image shows the facial differences between an ancient modern human with heavy brows and a large upper face and the more recent modern human who has rounder features and a much less prominent brow. The prominence of these features can be directly traced to the influence of the hormone testosterone.