Biomimicry

by Janine M Benyus

  Did resourcefulness like this advance the whole era of tool using? Sauther concludes that the responsibility of being a mother may not have been a burden but, rather, a “catalyst for developing more efficient foraging techniques.” A sensitive stomach, a new habitat, and the hungers of pregnancy were perhaps the literal mothers of invention. Chances are also good that those females who were very good at finding year-round food in seasonal habitats went beyond “just surviving” and began to tap the power of limits. Branching out from their standard fare, they may have actually garnered better nutrients and therefore provided their young with the metabolic stuff needed to develop a bigger brain.

  Many millennia later, what have we done with all those smarts?

  What Can Animals Teach Us About Smarter Diets?

  It appears, as the whole country idles in the drive-through lane of Burger World, that we’ve lost our dietary way. Even the most nutrition-savvy of us can have a hard time keeping Oreos in the house for more than a few days. In America, where 30 percent of the population is obese and suffering from diseases that are aggravated if not caused by poor diets, we could use a crash course in choosing nutritious foods.

  What’s strange is that feeding behavior—specifically food selection—is one of the last things that has been examined in both human and nonhuman primate studies. For all we know (and we don’t), humans may have originally learned to gather food by watching what other primates ate. Today, there are still some overlaps in the diets of human societies and animals in the same habitat. Says Bernadette Marriott, “Many of the foods that monkeys in Nepal gather are ones that people also gather, although those practices are going by the wayside as we introduce people to commercial foods. After doing nutritional profiles on these [native] foods and seeing how rich they are, we are now trying to encourage people not to give up on their wisdom, to eat more of these widely available plants rather than buying Western food.”

  In many places, we are too late; people have already gotten away from eating what the animals eat. The Green Revolution of the 1960s “converted” whole nations from a relatively healthful, native-derived crop diet to one of foreign-bred wheat, rice, corn, oats, and so on. Everywhere, farmers have abandoned local plants that were hardy, disease resistant, and well-suited to their climate, and are instead growing plants imported from other regions, plants dependent on chemical and petroleum companies for their yields.

  Now the cycle is coming back around—after dangerously homogenizing our crops, we are reevaluating wild varieties. It might make more sense, we’re admitting, to grow yams from local breeding stock than to import Idaho potatoes that have half the flavor and twice the water and pesticide requirements.

  To round out the crop choices for more bioregional agriculture, we may want to enlist the help of animals that have already forged a clear path through the chemical jungle. Unhampered by the blinders of human custom, they might lead us to crop lines that, though new to us today, are old standbys of the primate clan.

  MEDICINAL EATING: ANIMAL PHARMACISTS

  From here, it’s not such a long leap to imagine that animals might have more than one relationship with the green plants that surround them. They might, for instance, regard certain plants not as food but as medicine that helps them feel better when their systems are out of whack.

  “Out of whack” can mean that parasites have come to call, or that bacteria are multiplying. Plants fend off bacteria, viruses, round-worms, nematodes, or fungi by producing secondary compounds. If these compounds were placed inside an animal gut, might they offer the same antibacterial, antiparasitic, or antifungal protection? And might the animals notice this and seek out treatments when needed? After all, if they’ve learned to avoid toxic secondary compounds, couldn’t they just as easily learn to harness the beneficial ones?

  Animals acting as their own pharmacists. We shouldn’t be surprised, but we are.

  Plop, Plop, Fizz, Fizz

  From where Michael Huffman sat, relaxed, primatelike, slanting glances from his peripheral vision, he could see the chimp they called CH. As we humans would say, she was not herself. Lethargic, unable to roust herself from her tree nest, CH hardly noticed the intense feeding activity all around her. Over the last few days, her urine had been dark and her stools infrequent and irregular—classic symptoms of roundworm or schistosomiasis infection. That morning, CH suddenly struggled up and staggered off into the jungle of Mahale Mountains National Park, located on the eastern shore of Lake Tanganyika in western Tanzania. Huffman, a primatologist from Kyoto University in Japan, and Mohamedi Seifu, of the Mahale Mountains Wildlife Research Center, grabbed their notebooks and followed.

  Chimpanzees (Pan troglodytes) have an uncanny knack for finding their way in the jungle and for remembering and anticipating ripening food trees. This orienteering ability, as behavioral biologist Richard Estes calls it, allows them to get from wherever they are to wherever they want to be via the shortest route. Even though she was ill, CH seemed to know exactly where she was going, and she didn’t stop moving until she reached the flowering Vernonia amygdalina shrub. It was a plant that chimps don’t normally eat, but one that people in many parts of Africa use for traditional medicine. With painstaking care, she selected several young shoots and began to strip off the leaves. Using her front incisors, she peeled back the bark, exposing the liquidy pith. Grimacing like a coed downing a shot of tequila for the first time, she chewed the branches and sucked out the juice.

  Huffman watched CH carefully after her “treatment,” and, sure enough, within twenty-four hours she was defecating regularly, foraging for longer periods, and eating with the rest of the troop. When chemists later tested the plant, they found two secondary compounds in the pith—sesquiterpene lactones (terpenes) and steroid glucosides—both of which were shown to have exceptional antiparasitic activity, strong enough to kill a wide variety of gut parasites without killing the patient. Sometime later, Huffman was lucky enough to see a second chimp seek out the pith. This time, he was able to monitor the chimp’s parasite levels (by checking feces), watching them drop to harmless levels within twenty hours of treatment.

  Once he knew what to look for, Huffman realized that a lot of chimps were using Vernonia pith, especially during the wet season when worms are abundant. Despite the fact that this particular species of Vernonia plant is rather rare in the Mahale Mountains, both the chimps and the native people have zeroed in on it. Vernonia amygdalina is called “bitter leaf” by the Tongwe natives, who use it when they are afflicted with similar malaise, loss of appetite, and constipation. The pith contains a perfect dose of the juice, about the same amount as in a typical dose used by humans. Further analysis revealed why the chimps focus only on the pith—elsewhere in the plant, in the leaves and bark, for instance, the parasite-slaying toxins are in concentrations high enough to kill lab mice.

  Encouraged by the antiparasitic qualities of this one plant, researchers have begun to investigate the entire Vernonia genus. Clinical tests of a closely related plant (V. anthelmintica) have yielded a compound that could be used to treat pinworm, hookworm, and Giardia lamblia in humans. “Standard wisdom is that these [secondary compounds] are toxic or dangerous to animals,” writes Richard Wrangham. “But over the last fifteen or twenty years, a series of anecdotes has jelled into studies suggesting that animals can use those compounds to their own benefit, often turning the toxic effects against their own internal enemies.” So much for standard wisdom.

  Take Two Leaves

  Another clue to the puzzle showed up a few miles from Huffman’s post, in the Gombe Stream National Park in Tanzania. A troop of chimps living in Gombe are among the most scrutinized animals in animal behavior history. For more than three decades, primatologist Jane Goodall has trained many an observer there, including Harvard anthropologist Richard Wrangham. Wrangham says he became a believer in animal self-medication when he witnessed something one early dawn, before any of the other researchers were on their “beat.”


  “A chimp I was observing had woken up sick,” he tells me, “and instead of rolling over for more sleep, she got up and began walking, making a beeline really. I had to hustle to keep up with her. Twenty minutes later she stopped at an Aspilia plant [a cousin of the sunflower that grows as high as six feet] and began a most unusual ritual.” The chimp began carefully inspecting certain leaves, even holding them in her mouth while they were still attached to the shrub, abandoning those that didn’t suit her. Finally, she plucked a small leaf and tucked it under her tongue, the way we might pop a nitroglycerin pill. She let it linger there, rolling it back and forth a little, but not chewing. Richard wondered if she might be absorbing something from the leaf through the mucous membranes under her tongue.

  From his hiding place, he watched in amazement as she puckered up her face and swallowed the hairy leaf, which must have been like swallowing a patch of fuzzy leather. He watched her swallow a dozen more leaves at a slow rate (five leaves per minute swallowed as opposed to the normal thirty-seven leaves a minute for leaves that are chewed) before she moved back to the troop.

  It was obvious from her grimace that this was not a taste treat, but Wrangham couldn’t automatically assume it was medicinal either. “Feeding studies are tricky,” says Wrangham. “It’s not enough to check ‘eating’ or ‘not eating.’ You have to catalog which chimp is eating which leaf from which plant, and then count exactly how many leaves it eats.” Even then, as Karen Strier, an anthropologist at the University of Wisconsin in Madison, reminds me, you may not have any useful information. “The digestive tract is a black box,” she says. “You don’t really know what the animal ‘makes’ of what it eats—whether compounds are absorbed or destroyed in their journey through the body. Your only clue is to analyze what’s left of the food—what comes out the other end in the feces.” Indeed, what remained in the feces after the strange leaf swallowing—a handful of nearly intact green leaves—become a signature clue for Wrangham. If the leaves were not digested, then what purpose were they serving?

  Though chemical analysis of the ingested leaves showed no conclusive proof of “medicine,” Wrangham began to see more and more of the strange leaf-swallowing behavior. One troop of chimpanzees in Kanyawara, a community of Kibale Forest National Park in western Uganda, seemed to be increasing their intake of leaves during certain times of year. Sure enough, when he looked over a sequence of months, he saw that the spike in leaf-swallowing behavior coincided with the months of heaviest tapeworm infection. This was the first time that leaf swallowing was correlated positively with a specific parasite infestation. Wrangham also noticed that the dungs with whole leaves in them also contained tapeworm fragments. It seemed as if the leaves, hairy and whole, might have caused a motile fragment of tapeworm to be shed from the gut and then carried off with the feces.

  Meanwhile, in the Mahale Mountains, Huffman was also finding spikes in leaf-swallowing behavior during the rainy season, when loads of parasitic nematode worms tended to be higher. Could it be that the chimps were downing more leaves at that time for the same reasons we buy more cold medicine during the cold and flu season?

  The latest theory is that the abdominal pain caused by nematodes or tapeworms causes chimpanzees to increase leaf swallowing, just as a tummy ache might cause your dog or cat to go out and eat grass. What researchers don’t yet know is whether the worm-purging effect is chemical (worms repelled by medicinal compounds) or mechanical (worms being combed out of the gut by the hairy leaves). Nevertheless, something about Aspilia seems to be affecting parasites, and the chimps know that.

  To find out what else they know, researchers are now looking for other plants swallowed whole by primates. In a chapter of the 1989 book Understanding Chimpanzees, Richard Wrangham and coauthor Jane Goodall report that Ugandan chimpanzees have been seen swallowing the leaves of the Rubia cordifolia. Of the 401 chimpanzee fecal samples he collected in Kibale, Wrangham found Rubia leaves in 16. All were whole and without tooth marks—signs of the same down-the-hatch fate that befalls Aspilia leaves. An analysis of the leaves uncovered a triterpene called rubiatriol, some bioactive anthraquinones, and most exciting of all, a cyclic hexapeptide that is “an extremely potent cytotoxic agent which is being investigated by the National Institutes of Health as a therapeutic agent for cancer patients.”

  Suddenly, with the verified connection to possible cancer-fighting ability, these compounds found in a far-off jungle were no longer molecular footnotes. And the grimacing feeding sessions were no longer anomalies. It was time to put the self-medication anecdotes to the laboratory test.

  First on the list was Ficus exasperata, which is thought to kill nematodes, an important intestinal parasite of chimps. The chimps concentrate on the young leaves, which have six times as much of the active compound (5-methoxypsoralen) as the old leaves. According to Eloy Rodriguez, a plant biochemist at Cornell University, the leaves and fruits of Ficus do a good job of killing the food-poisoning bacteria Bacillus cereus without harming Escherichia coli, the good bacteria that live in the gut. Many more leaves are waiting for chemical examination. Among the fifteen plants shown to be swallowed, not chewed, are Aneilema aequinoctiale, Lippia plicata, and Hibiscus aponeurus. Researchers are also collecting any plants that are eaten only on rare occasions or that are rubbed on the animal’s fur instead of being swallowed.

  Wrangham’s next big project is a study of diet differences between monkeys and apes such as chimps. As mentioned earlier in this chapter, monkeys can tolerate secondary compounds better than chimps can. Therefore, says Wrangham, “watching what monkeys eat and what chimps avoid may lead us to some interesting secondary compounds—possible drugs.” Plants that both species avoid are likely to be loaded with secondary compounds, substances that even local healers may not know about. The only problem with this approach, Wrangham tells me, is that it may have come too late for many species of plants. “Every time you take a leaf in to be analyzed,” he says, “you wonder if you’ll be able to find the species in the wild again.”

  Awash in Evidence

  Why have we waited until it is almost too late to start this quest? The early 1980s was the first time scientists speculated (in print at least) that primate leaf-swallowing behavior might be connected to self-medication. And yet we’ve known for a long time that rats “treat” themselves by swallowing clay after ingesting poisonous amounts of lithium chloride. In fact, experiments have shown that if the rat even thinks it was poisoned, it will eat clay, which is thought to absorb the toxic load. In the same way, as every pet owner knows, when a dog takes itself outside for an aperitif of grass, it is looking to purge what ails it.

  “Why we thought that hominids were the only ones who could discover the curative properties of plants, I don’t know,” says Wrangham. “We’re not the only animals in the jungle.” Wrangham also figured he was not the only researcher who had noticed animals self-medicating. When he and Eloy Rodriguez decided to hold a symposium at the 1992 American Association for the Advancement of Science (AAAS) meeting, scientists came out of the woodwork with their stories. The field of zoopharmacognosy was born.

  At that meeting, Jane Phillips-Conroy of Washington University in St. Louis gave an account of baboons near Awash Falls in Ethiopia that live in the ideal “controlled” experiment, set up by geographical differences in their home ranges. Two populations of the same species of baboon (Papio hamadryas) live near Awash Falls; one population feeds exclusively above the falls, the other below. The population below the falls is vulnerable to a snail-borne schistosome (Schistosoma cercariae), a fluke worm that causes a debilitating disease in primates, including humans. Above the falls, the snails are free of the fluke worms.

  Also distributed above and below the falls is Balanites aegyptiaca—a plant whose berries and leaves contain a steroidal saponin called diosgenin, a compound known to be active against the fluke worm. Native peoples have long used Balanites for controlling infections of schistosomiasis, and so, it would seem, do baboo
ns. In fact, although both populations of baboons have access to the healing plant, the only baboons that eat it are the ones that live with the infected snails. This led Phillips-Conroy to speculate that the plant was being sought out for something other than nutritional purposes, or else both populations would partake of it.

  Another tale was told at the meeting about two populations of mantled howlers, tree-dwelling monkeys that are habitually plagued by parasites. Researchers in Costa Rica were surprised by the stark contrast in parasite loads between two populations living in different parts of the tiny country. Howlers in Hacienda La Pacifica were heavily parasitized, while howlers from Santa Rosa National Park carried surprisingly light loads. Searching for reasons, the researchers noticed that Santa Rosa, with light parasite loads, had plenty of fig trees (Ficus spp.), while La Pacifica had none. Knowing that humans use the latex in fig trees as an antiworm medicine, researchers at the conference theorized that a compound in fig leaves or fruits may be keeping worm loads under control in the Santa Rosa howlers.

  Another unusual finding was the howlers’ utter lack of gum disease or tooth decay. Could howlers be brushing and flossing regularly? More likely, say researchers, it has something to do with the pedicels (stalks) from the cashew (Anacardium occidentale) that they are known to eat. An analysis of the pedicels showed high amounts of the phenolic compounds anacardic acid and cardol, both of which kill gram-positive bacteria such as Streptococcus mutans—the critters that cause tooth decay in humans.