My guess is that average individual brain size and intelligence just isn't as important in collaborative society. Once you start sharing knowledge (orally at fi

My guess is that average individual brain size and intelligence just isn't as important in collaborative society. Once you start sharing knowledge (orally at first, written later), you don't need everyone to figure everything out on their own. There's a also a huge variation in human brain size. [1] suggests almost a factor 2. I don't know if variation was similar 70.000 years ago. [1]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4262916/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4262916/