Natural selection seems to have selected us from ancestors that mostly followed herds of ruminants around and ate them in place of vegetation that we can't digest.
Absolutely—but they didn't factory farm and the herds of animals were healthy and in their natural habitat. The grand scope of agricultural waste is pretty disgusting. Just look at North Carolina:
https://www.ehn.org/hurricane-florence-floods-north-carolina...
Now imagine there was no hog farms and it was all regular plant crops and/or vegetation.
Before your edit, I assumed you were not being serious. Regardless of the claim that meat and dairy cause health issues...
Bad diets generally do not make people die during the period where they are able to have children. Natural selection has very little effect. Even if it did, the time period it would take for these effects to matter is significantly longer than most people care about when confronting the climate crisis that requires immediate action.
https://deniseminger.com/the-china-study/
Natural selection seems to have selected us from ancestors that mostly followed herds of ruminants around and ate them in place of vegetation that we can't digest.