Anthropology

beasts felled by other carnivors which is why their brains grew 70% bigger. We were scavengers. The marrow and the brains were the only thing the hunting carnivores could not eat. Humans could crack open bones with tools once the carnivores had left because they had hands and stone tools. The brains and marrow were a bit protected from spoiling as fast as the meat. They also contained building blocks for proteins like amino acids and fats.

Maybe 40,000 years ago the humans were hunting the big game themselves and maybe eating less marrow and brains? Then farming started.

Could be what happened.