Well, we already knew that, not enough grubs and worms included - but scientists have determined that plenty of carbs were also involved in development of big brains.
Starches, converted to glucose by cooking were essential to brain energy and fetal development, and could not be provided by an all protein and fat diet.
The Importance of Carbs in Human Evolution
Starches, converted to glucose by cooking were essential to brain energy and fetal development, and could not be provided by an all protein and fat diet.
The Importance of Carbs in Human Evolution