A paper I co-authored about the possible optimal diet of late upper paleolithic humans in the South West of France showed that the primary constraint on their diet was fat. It was a long time ago, but as I recall the prevalent meat was roe deer, and that's very lean. Solving the linear programming problem for the nutrients showed that they needed nuts to get the fat content.
[+] [-] ColinWright|7 years ago|reply
[+] [-] fifnir|7 years ago|reply
(I did try to google it but didn't manage anything)