A Straight Dope Classic from Cecil's Storehouse of Human Knowledge

Are humans meat eaters or vegetarians by nature?

June 8, 1990

Dear Cecil:

Is man a meat-eater or a vegetarian by nature? According to the enclosed clipping from a vegetarian magazine, "The intestinal length of carnivores (meat-eating animals) is three times the body length to allow for quick removal of flesh wastes that putrefy in the intestines. Man's intestine length, like other herbivores, is six times his body length and is designed for digesting vegetables, grains, and fruits." I'm not a meat-eater but my girlfriend is and she is not convinced man is a natural vegetarian. We decided to leave it up to you. (Why I agreed to this I don't know, it's obvious from your aggressive tone that you like your steak rare.) Please, don't embarrass yourself by quoting that garbage from the National Beef Council that meat is our best source of protein. Even high school kids know better than that.

Cecil replies:

Listen, wimp — whoops, too aggressive. Gimme some of that tofu burger. Ah, I can feel the testosterone receding already. Now then, let us reason like gentlemen. There are some intelligent arguments for vegetarianism, but claiming that man is "naturally" herbivorous isn't one of them. The settled judgment of science is that man is an omnivore, capable of eating both meat and vegetables, much as certain four-year-olds might like to convince their mothers otherwise.

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.

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.

Vegetarians go ape

Dear Cecil:

Your statement that "we were born to eat meat" is nonsense. In using comparative anatomy to determine what man was "meant" to eat, we should look at the species most similar to man, namely the anthropoid apes — chimpanzees, gibbons, gorillas, and orangutans. Of all animals, man's digestive organs and teeth most closely resemble these apes. In captivity, some of these animals will eat meat if forced to rather than starve to death. But in the wild, all eat a vegetarian diet.

Another strong clue that man is naturally a vegetarian is the fact that vegetarians in general are much healthier than omnivores. The American Dietetic Association has acknowledged that vegetarians are less at risk for a number of chronic diseases, including heart disease, some types of cancer, obesity, high blood pressure, and adult-onset diabetes.

Eating a healthy diet goes far beyond cutting back a bit on red meat. In a recent study of 6,500 Chinese, Dr. T. Collin Campbell of Cornell found that even though the Chinese overall eat only a fraction of the animal protein Americans do, those who ate the least animal protein nonetheless had lower risk of disease than the average Chinese. Dr. Campbell concludes, "We're basically a vegetarian species and should be eating a wide variety of plant foods and minimizing our intake of animal foods."

Cecil replies:

I feel like I'm arguing that the Pope is Catholic. To clarify a point that eluded many who wrote me about this: the issue is not whether vegetarianism is healthier, better for the planet, etc., than the standard U.S. diet. I don't doubt it is. It's whether humans are naturally vegetarians.

Here it seems to me the best evidence is our history as a species. 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.

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. 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.

There's one in every crowd

Dear Cecil:

In reading through your column "Vegetarians Go Ape," I noticed an unusual fact that you seemed to expose with great confidence. You stated that "Jane Goodall established more than twenty years ago that wild chimpanzees kill other animals once in a while and eat the meat with relish." I question the accuracy of this. Where would wild chimpanzees obtain relish?

Make that two in every crowd

Dear Cecil:

You obviously know everything. Is it true Stanley and Livingston penetrated darkest Africa wearing pith helmets because they knew they would find no plumbing there?

Cecil replies:

Oh, pith off.

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