“Teamwork is the signature adaptation of” humanity, says David Sloan Wilson. And our ancestors evolved ruthlessly cooperative means of ensuring productive social coordination.
Almost every point connects to the division of labor between hierarchical and distributed approaches. And recent research indicates that this happened about 50,000 years ago when groups selected for men who had less testosterone, allowing for more cooperation.
But the same research shows that this is being reversed.
Looking at 1400 skulls, the researchers looked at bony structures of the skull that are known to be modulated by testosterone levels – like brow ridges.
They found a morphological change occurred at just the same time we see huge changes in human behavior and artifacts at 50,000 before the present.
Male skulls from the successful societies after this time are much more feminine in appearance than before. Those groups that could more easily cooperate could not only find better sources of food but could also raise their children easier.
Here is the summary slide from the paper:
So we see a tremendous change in brow ridges and skull shape as we move towards the present, with recent hunter-gatherers being the most extreme.
But what is interesting is that in modern societies, where hierarchy is often a more successful strategy than collaboration, we see a regression.
Testosterone once again became a more important aspect of society.