[yamtaddle]

> Our ancestors who knew how to raise cattle and farm cereals for millennia were surviving on the verge of starvation : why do you think that was ? Were they so dumb they'd rather die of hunger than convert some of their grazing pastures to cereal agriculture ?

This is one of those "not even wrong" kind of things. The conditions that led to famine-cycles plaguing the Old World until the arrival of New World crops, and later the Green Revolution, have nothing at all to do with modern farming or land use, not even in the way you're trying to make the connection. This is all just completely irrelevant to the point you're trying to use it to make.

"Were pre-contact old-world farmers just too dumb to kill their cows so they could plant more wheat and stop starving every few years?", asked rhetorically to imply that reducing meat farming can't possibly help with any modern problems. I mean... it's just a nonsense question, the context they were operating in, the global population size, and their farming practices are so far removed from what we do now that it doesn't make any sense to frame it this way. No, they weren't too dumb to think of that, and no, it wouldn't have helped if they had tried it, but neither of those things are relevant to the modern situation, at all.