I think "what nature intends" is just a way of asking what do our bodies do best with. For all the weird grab bag mess of evolution there are clearly things our

I think "what nature intends" is just a way of asking what do our bodies do best with. For all the weird grab bag mess of evolution there are clearly things our bodies process and gain nutrition from better than others. For all our ability to be "gaping maws" as you put it we can't eat grasses enough to feed ourselves properly like a cow, our bodies aren't built to extract the requisite nutrition from that with our single stomach. It's often deployed to argue that fad diet X or Y is what's best but it's not completely bunk science that there are diets that are better or worse for our health than others.