So a long time ago there was a brutal and very long ice age that severely impacted the ability for plants to grow, especially edible ones. Any humans slightly above or below the equator could really only get calories by killing and consuming animals. During this time humans adapted to be hyper-carnivorous.

Anthropologists have analyzed bones from humans of that time and found they had the highest carnivore rating of any bones studied from that time. Our species really only ate meat for thousands of years, even eating the other carnivores, which is why our rating was the highest. That and we’re smart and excellent at killing. Humans are Apex predator hyper-carnivores.

Our bodies specifically adapted to eating meat and this shows in many ways in our physiology. Plants and especially grains and sugars are toxic to humans. We can survive on those foods, but sub-optimally. Habitual consumption of non-animal product foods is a significant detriment to lifespan. As we can see today with record high levels of cardiovascular disease, diabetes, cancer, heart disease, neuro-degenerative diseases and obesity.