Let’s check in first with our closest cousins. I e-mailed Jill Pruetz, the Iowa State University primatologist whose work with chimpanzees in the Fongoli River region of Senegal I profiled for a magazine in 2007. By coincidence, Pruetz and her colleague Paco Bertolani had just submitted a paper on the topic. “I don’t like to think of the Fongoli chimps as shit-eaters,” she wrote back, “but what are you going to do?” For one thing, you call it “seed reingestion.” Technically speaking, this is accurate. Fongoli chimps don’t, as they say, “consume the dung matrix.” They “excrete a faecal bolus into one hand and then extract the seeds from it with the other hand or with the lips.” You may be pleased to note that when they are done they “clean their lips by rubbing them on the bark of trees.”
Pruetz’s team observed seed reingestion only during the span of weeks when baobab and Fabaceae seeds are too hard to chew. During this time, it takes a second run through the digestive tract to dissolve the hulls and release the proteins and fats in the kernel. Women in the Tanzanian Hadza tribe use a similar technique, harvesting softened baobab seeds from baboon dung, washing and drying them, and pounding them into a kind of flour.
Before you get all high and mighty on the chimps and the Hadza, you should know that the most expensive coffee beans in the world—at upwards of two hundred dollars a pound—are those that have passed through the digestive tract of the civet, a catlike animal native to Indonesia. The animal’s digestive enzymes are said to alter the taste of the beans in a pleasing manner. The trade is lucrative enough to have spawned a market for counterfeit civet dung, crafted from ordinary undigested coffee beans, a dung matrix of similar consistency, and glue.
Though seed reingestion is most prevalent on the savannah, where food is scarcer, it also happens in the rain forest. Pruetz’s paper cites the work of a team of researchers who observed coprophagy in wild mountain gorillas. At a loss to explain the behavior, given the relative bounty of the surroundings, the researchers suggested that it might have been done for the same reason people reach for the Cream of Wheat on a midwinter morning. “They proposed,” Pruetz wrote to me in an e-mail, “that mountain gorillas might like to eat something warm during periods of cold temperatures or heavy rain.”
And now, with all apology, it’s time to move on to Homo sapiens. A 1993 study of “humans behaving in a manner similar to nutrient-deficient animals” involved three institutionalized patients, Bart, Adam and Cora, all with profound developmental disabilities. Charles Bugle and H. B. Rubin successfully broke the trio’s autocoprophagia habits by feeding them a nutritional supplement drink called Vivonex. The authors speculated that this population “often has multiple handicaps and something may be missing that makes it more difficult to digest or metabolize all the nutrients in the diet they are served.” Whether or not this is true, a glass of Vivonex is preferable to some of the alternative strategies tried by staff at other institutions. In particular, that of the team who “treated . . . coprophagia and feces-smearing by making a shower contingent upon the absence of feces.” You can see where that could go south pretty fast.
THERE IS ONE class of substances that the rectum, even today, is occasionally called on to absorb. Drugs take effect faster this way than by mouth, partly because they bypass the stomach and liver. Opium, alcohol, tobacco, peyote, fermented agave sap, you name it—it’s been taken rectally. In the case of certain South American hallucinogens, rectal indulgence also allows one to sidestep vomiting that accompanies the oral route. Considerably enlivening the pages of Natural History in March 1977, Peter Furst and Michael Coe described the heretofore unrecognized prominence of the “intoxicating enema” in classic Mayan culture. The discovery came about with the examination of a painted Mayan vase from circa 3 A.D. that had previously been hidden away in a private collection. The decorative embellishments feature a man in an elaborate pointy hat but no pants, crouched like a cat, hind quarters raised, while a kneeling consort holds a tubular object to his anus. Another man squats, administering to himself.