PyramidHead
Contributor
Therefore herbivores don't exist.The other salient piece of information we have about human dietary needs is that agriculture had to be invented.
In other words, there was not enough energy-rich vegetation and sweet fruit in the natural environment of humans to satisfy their desire for it. This same environment was what would have exerted selection pressures on our ancestors, so it seems unlikely that plant matter would have been absolutely crucial to human life before we had the means to reliably grow it. I keep returning to this point, but the planet has changed a lot more than humans have in the past few hundred thousand years. Dependence on a food source that varied seasonally, was unavailable during ice ages, and was low in energy content would have put early humans at a severe disadvantage compared to those who could subsist on just meat--available anywhere animals live, in any climate, and full of energy. Thus, if we had some kind of nutritional requirement for something that could only come from plants, I don't see how that requirement would have survived natural selection before the invention of agriculture.
Or wasn't that the conclusion you were working towards there?
What did herbivores do during ice ages?
Their teeth changed shape, their blood evolved to retain more hemoglobin, they evolved long, thick coats, they learned how to hibernate, or they grew wings and flew someplace more temperate. Human remains from those periods are basically identical in all such ways to modern humans, suggesting that they, like the carnivores who survived alongside them relatively unchanged, simply stuck it out and lived on animal flesh. What else could they have done? Or did a new genetic lineage of plant-dependent humans evolve for each ice age and then die out without leaving any traces?