Agriculture has only been around for approx. 10k yrs compared to 2.5M yrs for the Homo genus.
It seems to me we are far better adapted to eating meat/fish then products of agriculture (i.e. carbs).
Before agriculture there was horticulture and before that there was hunting/gathering - with gathering being the much more dependable.
Humans in the wild still gain the majority of their calories from carbohydrates. Meat and fish are a major source of necessary protein - but the vast majority of energy was still derived from carbohydrates.
Our molecules of metabolism are set up to burn carbohydrates as the primary energy source.