Among the new college textbooks that just came out for general biology, two contain a new diagram that shows the authors know nothing about where our meat comes from.

Under the title of “Ecological Pyramids,” the book shows a field of corn supporting 10 people. To the side of this, they show the same field of corn feeding cattle that in turn produce enough meat to feed one person.

The simple-minded message is if we eat corn rather than meat, the earth can support 10 times more people. This “10-percent rule” is a general concept we use in describing energy loss in food chains in nature. Unfortunately, the authors who designed this simplistic graphic knew nothing about growing corn or cattle ranching. The conclusions that students are to draw about the 10-fold benefit of everyone going vegetarian are biologically wrong. And the problems are many.

• Humans consume only the small portion of highly nutritious corn kernels (plant embryos) from the total biomass the plants produce. Cattle are not picky vegetarians. They feed on stalks and leaves as well.

• There is an efficiency difference between eating plant and animal tissues. Meat-eating is more efficient. Animal tissues are made of chemicals similar to what we need. But plant cellulose is indigestible by humans. Humans have to eat more vegetable matter biomass to get the calories and nutrients we need.

• Cattle forage heavily on grass, not corn; this is where most of their biomass comes from.

• A cow’s stomach is a rumen designed for fermentation of plant roughage. Their primary food source is grass and hay, etc. Feedlot operations that are used for some, but not all, beef cattle are finishing up the animal for the addition of fat marbling in the meat to attain a higher meat grade. The corn kernels that constitute the only food for humans does not constitute the totality of the animal’s biomass. The textbook mathematics is pseudoscience.

• Drive through the Flint Hills and across parts of western Kansas where road cuts reveal the soil is only a few inches thick. No crop land there. Humans can either eat the grass, the grasshoppers or the beef. Take such lands out of cattle production, and you decrease the world’s food supply — period. I work each summer in China, and the meat available there is grown by animals that feed on peripheral “edges” that cannot be farmed, animals that never see a feedlot, and from pigs that mostly recycle food wastes. End these sources of meat, and there is no cropland saved to feed more people.

• Wolves and other carnivores might eat nothing but meat, but humans are omnivores. Our prehistory, our teeth and our nutritional requirements show we have evolved to eat both plant and animal tissues. But the textbook shows a single person eating nothing but meat, a strawman argument that does not exist in the real world.

Why are textbooks only now beginning to run these incorrect examples? The number of persons with rural farm experiences nationwide has dropped from nearly 40 percent at World War II to well under 1 percent today. But it is not just a case of a city scientist writing about something he doesn’t know about. College training has likewise shifted away from field experiences working with plants and animals, and toward biochemistry and molecular biology.

Still, printed textbooks are supposed to be reviewed by other scientists before being published. Unfortunately, in the era of online materials that are hugely laden with errors, there is reason to believe textbook publishers are letting down their guard. Textbook reviewers should have caught this.

Fortunately, well-trained biology teachers can send these textbook samples back to the cooks and not accept them until they are well done.

John Richard Schrock is a professor

in the Department of Biological Sciences at Emporia State University.