Everything about old history and how to get information about old time
Good article. It touches on most of the obvious possible causes and effects already.
less need to be intelligent to stay alive?
How come no tattoo
Better wiring, humans are still under strong evolutionary pressure especially with society creating disease risks. Why support a large costly organ when better connections can do the same job. See also bird brains, lightweight and powerful
Lack of iodine.
I'd wager it's somehow related to us being persistence hunter. Some sort of CTE from marathon running advantages people with a bit of space in their skull. That would be my guess.
Hmm...