I'm forgetting, but I do think women in the keto groups had a hard time producing milk. Again, probably a male/female difference. Breast milk is low fat & even low protein (only about 5-7%). It's mostly carbs/sugars, which I know can translate within us from glucogenesis, but it doesn't seem to fully sustain a lactating mother.

Grains are newer in human evolution, though. They obviously go along with farming & agriculture. They can also be - & often are - stored for upwards of a decade. Ewww. We really don't need them, they just became convenient & filler food.