Animals eat other animals, why shouldn't we?
Short answer: That animals kill each other is a fact about nature, not a moral instruction. We don't model the rest of our ethics on what a lion does.
We don't find these animals in a wild food chain. We breed roughly 80 billion land animals into existence every year to slaughter them.
FAO / FAOSTAT via Our World in Data (2021)
The objection
“Eating meat is just nature. Lions do it, wolves do it, the whole food chain runs on it. Why should humans be the one species that pretends it’s above all that?”
The answer
Grant the premise completely: nature is full of killing. Predation is real, the food chain is real, and no one sensible denies it. What follows from that for a person standing in a supermarket is nothing.
This is the oldest move in the book, the appeal to nature, or the is–ought gap. That something happens in nature tells you nothing about whether you ought to do it. Disease is natural. Infanticide occurs across the animal kingdom. Males of many species kill rivals’ young and force copulation. You would never accept “it’s natural” as a defence of any of those, so you don’t actually treat nature as a moral guide. You reach for it only here, only when it licenses what you already wanted to do.
There’s a sharper problem. A lion has no alternative; you do. An obligate carnivore must kill to live and can’t weigh the ethics of it. You can. Invoking the moral standards of an animal that can’t reason, while you stand there with a hundred choices, just borrows a predator’s lack of options to dodge a choice you actually have.
We model the rest of our lives on the opposite principle. We build hospitals, punish violence and protect the weak; the entire project of civilisation is choosing not to do what comes naturally. The food chain explains why a lion kills. It was never an argument for why you should.