Commenter Melo (meLon Musk) recently linked to a paper arguing that the brain size of H Sapiens has been stable for hundreds of thousands of years. Already aware of the paper, I had emailed the lead author and he replied “You might download the DeSilava data set from their paper – it is open source. As far as I know, it has the most complete cranial volume data set (directly measured volume).”
Of course analyzing such an enormous data set is overwhelming so I decided to start with Middle Paleolithic brains (300 kya to 50 kya). There were 17 Sapiens skulls in the data set from this time period and these ranged from 1100 cc (Manot Cave specimen) to 1590 (skhul 9 specimen) with a mean of 1441 (SD 127). When I remove the two oldest specimens from the sample (the Jebel Irhoud pair which some argue are proto-Sapiens not fully Sapiens) the mean and SD increase slightly (1452, 129 respectively).
Overall, these brains look pretty damn big, especially since Sapiens hadn’t even lastingly left the tropics yet, but I’ll reserve judgement until analyzing other time periods.