Human brain Body Facts | 1 comment Human brains are 10% smaller than they were 20,000 years ago. Fact source 1 Comment Jeanne Christian on September 19, 2016 at 3:14 pm How do we know? Who was measuring brains 20,000 years ago? Reply Submit a Comment Cancel reply Your email address will not be published. Required fields are marked *Comment Name * Email * Website This site uses Akismet to reduce spam. Learn how your comment data is processed.