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Herbal medicine: Rx for chimps?

Herbal medicine: R(x) for chimps?

Dawn breaks on Tanzania's Gombe National Park, and several chimpanzees depart their tree-borne nests in search of an unusual breakfast. They pass up nearby fruit trees and take a 20-minute trek to a patch of grassland where they swallow--without chewing--the leaves of a shrub known as Aspilia.

Are the leaves a tasty addition to ape diets on the African savanna? Probably not. It appears that the chimps seek out a recently identified substance on the leaves that kills disease-causing bacteria, fungi and parasites, reports anthropologist Richard Wrangham in the latest ANTHROQUEST, the newsletter of the L.S.B. Leakey Foundation. Last year, Wrangham, of the University of Michigan in Ann Arbor, and two colleagues visited botanical research centers in East Africa and found that several African tribes similarly use the leaves, often swallowing them to ease stomachaches or rubbing them on surface wounds or cuts.

If the chimps are aping humans by intentionally medicating themselves to fight disease or reduce pain, says Wrangham, "we can envision a slowly growing use of [herbal medicines] by human ancestors over millions of years.'

Wrangham has observed more than 100 instances of Aspilia swallowing at Gombe and at another nearby site, Mahale Mountains National Park. Upon locating the 6- to 10-foot-tall shrubs, a chimp typically puts its lips around a single unplucked leaf, perhaps touching it lightly with its tongue. Several leaves are tried in this way before one is pulled off the stem. The animal rolls the leaf around in its mouth rather than chewing it. Within 15 seconds the leaf is swallowed, occasionally with a grimace. No more than 30 leaves are consumed over the next 10 minutes.

Chimps of all ages engage in this behavior, says Wrangham, but for some reason females use Aspilia about once every 10 days, while males use it an average of once a month. There are other mysteries: It is not known, for instance, why Gombe chimps swallow the leaves at dawn while Mahale chimps consume them at any time of day. Also, humans and chimps use the same three species of Aspilia and neglect a fourth species. The distinguishing qualities of the neglected species are unclear, notes Wrangham.

For many years, he says, chimp researcher Jane Goodall noticed that chimp dung at Gombe often contained one type of leaf that was never chewed.

But the function of the leaves, now known to be Aspilia, is just beginning to come to light. In April 1984, Eloy Rodriguez of the University of California at Irvine identified a red oil in the leaves, which he dubbed thiarubrine-A. A few weeks earlier, Neil Towers of the University of British Columbia at Vancouver isolated the same chemical from Canadian plants. He found that thiarubrine-A kills common disease-causing bacteria, fungi and nematodes, a type of parasitic worm.

In an electron microscope analysis of leaves retrieved from chimp dung, the two scientists jointly observed that surface cells containing thiarubrine-A were ruptured, probably during passage through the gut.

At that point, Wrangham and the two investigators visited East African research centers, where they found that some African peoples use Aspilia to treat a number of medical problems.

Chimps and people may have similar ideas about Aspilia, says Wrangham, but it is not clear what the leaves actually do. Perhaps they control owrms in the gut. Or, he notes, since chimps sometimes eat more after swallowing Aspilia, the plant might be an intoxicant. Animals in many areas of the world "get high' by consuming naturally occurring drugs (SN: 11/5/83, p. 300).

Wrangham and his colleagues plan to monitor in the laboratory the physiological reactions of chimps and other animals to Aspilia and thiarubrine-A. They also want to compare physiological measures in chimps who swallow leaves with those of abstaining chimps.

Wrangham's observations add to other recent findings concerning the eating habits of primates, points out anthropologist Randall Susman of the State University of New York at Stony Brook. Several primate species, for example, eat certain plants only when toxins are not present, such as early in the morning before the sun activates dangerous chemical compounds.

"The Gombe chimps appear to be actively seeking out certain plants, not just reacting to them,' says Susman. "I would expect similar behaviors to turn up among other apes.'

Baboons, which are not apes, do not swallow Aspilia leaves in Gombe, says Wrangham, although they occasionally eat foods that are poisonous to many other mammals. "When a baboon eats a fruit that would be toxic to people, it may merely be having a snack, rather than dosing itself with a drug,' says Wrangham. "It's exciting to find a case where curious behavior suggests deliberate intake of a powerful drug.'
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Title Annotation:chimpanzees seem to chew leaves for their medicinal value
Author:Bower, Burce
Publication:Science News
Date:Jan 18, 1986
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