Our Brain Was Always Growing And Growing. And Then It Stopped.

Previous research estimated that, over the past 20,000 years, the average volume of the human brain went from 1,500 cubic centimeters (cc) to 1,350 cc — shrinking by about 150 cc, or 10% (the size of a tennis ball, as commentators have pointed out.)

“Most people are aware that humans have unusually large brains—significantly larger than predicted from our body size. In our deep evolutionary history, human brain size dramatically increased,” said the new study’s other co-author James Traniello, of Boston University. “The reduction in human brain size was unexpected.”