Natural born omnivores

` Grargh! I was trying to post a science post, but the computer froze up before I could send it through and I ran out of library minutes! So... this one will have to do:

` Hail Cecil! Yes, I shall not write a 'real' post today, but rather recycle some Cecilage I've been saving up. This time, he tackles the question of whether or not we're best built for eating meat.

Like the hard-core carnivores, we have fairly simple digestive systems well suited to the consumption of animal protein, which breaks down quickly. Contrary to what your magazine article says, the human small intestine, at 23 feet, is a little under eight times body length (assuming a mouth-to-anus "body length" of three feet). This is about midway between cats (three times body length), dogs (3-1/2 times), and other well-known meat eaters on the one hand and plant eaters such as cattle (20 to 1) and horses (12 to 1) on the other. This tends to support the idea that we are omnivores.

Herbivores also have a variety of specialized digestive organs capable of breaking down cellulose, the main component of plant tissue. Humans find cellulose totally indigestible, and even plant eaters have to take their time with it. If you were a ruminant (cud eater), for instance, you might have a stomach with four compartments, enabling you to cough up last night's alfalfa and chew on it all over again. Or you might have an enlarged cecum, a sac attached to the intestines, where rabbits and such store food until their intestinal bacteria have time to do their stuff. Digestion in such cases takes place by a process of fermentation--bacteria actually "eat" the cellulose and the host animal consumes what results, namely bacteria dung.

` Yummy.

The story is roughly the same with teeth. We're equipped with an all-purpose set of ivories equally suited to liver and onions.

Good thing, too. I won't claim meat is the ideal source of protein, but on the whole it's better than plants. Sure, soybeans and other products of modern agriculture are pretty nutritious. But in the wild, much of the plant menu consists of leaves and stems, which are low in food value. True herbivores have to spend much of the day scrounging for snacks just to keep their strength up.

So make no mistake: we were born to eat meat. That's not to say you have to. There's no question that strictly from a health standpoint we'd all be a lot better off eating less meat (red meat especially) and more fruits and vegetables. But vegetarians aren't going to advance their cause by making ridiculous claims.
We have been happily eating meat for at least two million years, and probably much longer. The common view among anthropologists, in fact, is that increased meat consumption was a key element in the development of human culture, since getting and distributing the stuff requires cooperation.

` In addition, it seems as though our most carnivorous ancestors - Homo ergaster, I believe - had problems because they ate too many animal livers, and the resulting overdose of iron (hemochromatosis) is evident from looking at their fossil remains.

Not all anthropoid apes are exclusively vegetarian. The primatologist Jane Goodall established more than 20 years ago that wild chimpanzees kill other animals once in a while and eat the meat with relish.

` Really? They have relish in the middle of the jungle?

Other primates (although apparently not gorillas) do so as well. It's true chimps and other apes eat a mostly veggie diet, but for that matter so do most humans. Hunter-gatherers today consume only about 35 percent meat to 65 percent vegetables (Lee and Devore, 1976). Anyway, we and the anthropoid apes diverged six to 14 million years ago--who cares what monkeys munch now?

Your argument that meat-eaters are more prone to chronic disease is irrelevant. Chronic disease typically strikes the old, not those of prime child-rearing age. Till recently most folks never got chronic disease because they died of the acute kind first. It's had minimal impact on our ability to reproduce ourselves, which of course is the basis of natural selection. In short, as we evolved, chronic disease did not "select out" for vegetarianism. I trust you see the significance of this.

There is much to be said for vegetarianism. I am at a loss to know why vegetarians cannot be content simply to say it, without taking the argument over a cliff.

--Cecil Adams

` Indeed. Nevertheless, I don't intend to change my plant-eating ways, seeing as my body is about 65% adapted to herbivory as it is. Just as long as I stay away from acute diseases.