Humans are omnivores obviously. Yes, some choose to be vegans and whatnot. But physiologically speaking we are omnivores.
This question has concerned me for years. I guess I can tell you, part of it is inspired by what life is like on other planets.
What if humans were herbivores? First off, how if anyway would that effect our psychology? Our culture? And what about our propensity to overpopulate? I am not implying that I know. I’m asking you.
And carnivores? Ditto for all the questions above.
Being omnivores is what helped us in times of food scarcity, particularly before we learned to farm or cook. So I suspect that we’d have been replaced by some other hominid species that were more omnivorous.
Our brains also need higher calories to function. So we’d also likely be less intelligent, which is our main actual advantage that led us to the top of the food chain. If the bigger brains don’t evolve in other hominids that are omnivorous, then maybe none get to that level.
In short, I think our omnivorous lifestyle was a full on requirement for us to evolve to where we are today. What might be interesting, however, is if we then later lost these abilities due to some environmental adaptation, and then the environment changed back.
This basically requires the full worldbuilding of a SF novel to answer satisfyingly, IMO. BUT, I think it can also be answered like this: It’s unknowable. If we look at the spectrum of Earth wildlife and concentrate on the species close to strict herbivores, their evolutionary history and behavior varies a lot. Ditto the species close to strict carnivores. There are few behaviors that are exclusively one or the other, except for what they eat of course.
I’m skeptical we would have made it across the Bering land bridge without meat. Heck, I’m skeptical we would have made it far out of Africa during the Ice Age without meat.
Our relationship with domesticated animals would be different. Cats would still make sense to protect grain from vermin. Dogs might be harder – although they’d still have a place for guarding, the assumption is that camp dogs were attracted by and then fed with scraps. Hard to convince some wolves to hang around and eat your apple cores. Only function for cattle would be as draft animals (I assume “herbivore” precludes dairy), sheep for wool, no real role for swine, etc.
Would we bother raising animals for hides if we weren’t going to eat them? I suppose these days you have mink farms but even those are fed from meat processing scraps. If you had to find a way to feed them independently from human food production, I doubt anyone would bother.
I recall a somewhat common statement from years ago: “The great cattle drives weren’t primarily about the meat. The industrial revolution needed the leather because leather belts were used to distribute power from stationary steam engines to the individual machine tools.”
(The real situation was probably more nuanced, the need for food and the need for leather were probably running neck and neck.)
Maybe, but that came thousands of years after cattle were domesticated. Without the drive to keep large quantities of cattle in general (perhaps some for draft purposes?) I have to think we’d have landed on some different solution – assuming our new path got us to that place at all.
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