Whatever Happened To Omnivora?

Once upon a time, the word "omnivore" was Important. It carried the force of Science behind it. It Meant Something. And then one day, with hardly anyone noticing, it fell from grace, and found itself a mere colloquial description, with no real scientific meaning.

Lucky for it, though, only scientists seemed to have noticed. But who cares what they think?

Vegans run up against this legacy all the time. We're constantly told that humans are natural omnivores, that we're designed to eat meat, that our ethical/lifestyle choice is therefore unnatural. In some of its more sophisticated or elaborate forms, this argument makes appeals to evolution, drawing smart-sounding comparisons between the teeth of, say, lions and cows, or the guts of, say, apes and wolves. The goal is always to demonstrate that humans have more (or less) in common with one or the other of the "herbivore" or carnivore species, and to draw conclusions about our destiny from our alleged "design."

Vegans often fall into this trap, as well, arguing the reverse position from the same set of data, and basing their logic on the same tacit assumption. But no one ever questions the tacit assumption: namely, that there is a meaningful distinction to be drawn between "herbivores," "omnivores," and carnivores.

Paleontology and evolutionary biology have something to teach us here, something potentially profound. But while they've been going through a revolution, most of the outside world has been stuck on old debates informed by outdated terminology and rickity framing. The result is a tired fight that doesn't just sound worn out, but actually is.

This blog hopes to change that, in the service of both paleontology and veganism.

You may have noticed that I didn't put the word carnivore in quotation marks in any of the above paragraphs. That wasn't a typo. There is still some precision and meaning in that word, enough that it's given its own Order-level taxon in the Linnaean system: the Carnivora.

(Though, to be fair, I should have used quotation marks, because not all "carnivores" are Carnivorans, nor are all Carnivorans "carnivores.")

"Omnivore," as noted earlier, once had this honor, as well: sub-Order Omnivora. But no longer. Its title has been stripped away, the poor word consigned to the trash heap of colloquiallism, and all its species doled out to new taxons.

The story of why and how this happened is merely a footnote in the tale of a Renaissance that swept the life sciences a few decades ago, and is still sparking heated arguments among the fields' leading thinkers. It's a tale that makes paleontology one of the most exciting, cutting-edge and relevant geo-/bio-sciences of our time.

So here, without further ceremony, is the answer to the question: whatever happened to Omnivora?

The sub-Order Omnivora was formalized in Victorian times by the great anatomist, paleontologist, and opponent of Darwin, Sir Richard Owen, in Volume III of his seminal work, On The Anatomy Of Vertebrates (1868). The suborder, which he filed under Artiodactyla, included hippotomuses, pigs, hogs and several fossil mammal species.

It stuck around for almost a century, and during that time was expanded by some researchers to include bears and passerine birds. Interestingly, though, it never included humans or any other primate species.

It was eventually eliminated altogether from the classification scheme, and a quick glance at its members can tell you why: hippos, pigs, bears and birds. What the heck do those species have to do with each other?

That's a form of the question that got asked by Willi Hennig, the man who inadvertently started the current revolution in paleontology and evo-bio with the 1966 English-language publication of his book, Phylogenetic Systematics. The point of Hennig's question(s) was simple: the old system of Linnaean classification was too arbitrary. It gave taxonomists too much room for applying their feelings (for lack of a better word) to their work. We shouldn't be classifying species with each other based on how we feel about their behavior. So what if pigs, bears, hippos and birds are all "omnivorous"?; similarities in behavior are not a sufficient basis for meaningful classification scheme, according to Hennig. It produces too much confusion.

The question we ought to be asking, Hennig proposed, was, "how closely related are species to one another?" It's one of those questions in science that's profound in its simplicity. Hennig proposed a new taxonomic scheme that would have more logical and precise naming rules based on data organized according to genetic and evolutionary relationships, not behaviors or inference.

This simple set of proposals cascaded into a revolution that swept graduate schools in the 1970s and 1980s, then picked up steam in labs and field work in the 1990s thanks to the Internet and better computer modeling. It's thanks to this cladistic revolution that we now know that birds are actually dinosaurs, that whales are more closely related to cows than to any other mammal group, and that you are a bony fish.

It's also the reason the Carnivora got to keep their taxon, and the poor Omnivora got scattered to the winds. Turns out, the Carnivora all share a common ancestor, and the "Omnivora" don't.

So, what's this mean, bottom-line-wise, to the whole vegan-vs.-omni argument? There are two basic approaches we could take, but both end up at the same place.

One is to point out that almost all mammals are in some sense "omnivorous." The other is to point out that "omnivore" isn't a scientific term any more, and therefore isn't terribly useful. Both approaches stem from the fact that there's really no clear-cut dividing line between an "herbivore" and an "omnivore." In a real sense, the whole argument we've been having is irrelevant.

We humans, as mammals, can thrive on a wide variety of foods. The science backs that up. Humans can be healthy and vibrant as vegans, carnivores, or anything in between, provided they apply a little vigilance and common sense to their lives.

And ultimately, this means what I said in my very first post here: meat-eating is a choice. Nothing in human biology or evolution requires it. Therefore, it is fair game for ethical examination and, yes, judgment.

There's a lot more to say, but in the interest of brevity, I'll end it here. Future posts will talk about the development of anti-veg*ns' two favorite tropes -- human teeth and guts -- within the context of this new understanding of evolution. I've already stated the basic principles, though: human teeth are simply a variation of the standard mammalian dentition, and human digestive morphology is merely a twist on the standard primate gut. Neither is an adaptation to H. sapiens specifically, let alone to our dietary behaviors past or present.