I really don’t know for certain, but I think one reason why our ancestors did well was because they consumed every part of the animal, whereas we only tend to eat the muscle meat.
From my limited observation, I get the impression most that try and eat low carb don’t eat the full animal, in combination with going out of their way trying to consume as many raw vegetables as possible. I don’t think our ancestors would have done that.
However, I could have this all completely wrong.