Self-Medicating Chimps

The master of self-medication | The Chimpanzee | Pan troglodytes

[This one came from The Browser, a newsletter curation of good reading on the Internet. More on that later. SB SM]

These great apes are primates, like us. Sure, they’re a little hairier, but they’re hominids. Like us, these creatures are amazing. Like us? It’s a risky comparison. In many respects, chimpanzees are more accomplished. One talent they possess would benefit us, too: they know how to take care of themselves. Since the 1970s, researchers have known that chimpanzees — especially those in Tanzania or Uganda — use medicinal plants. They consume fruits with antimicrobial properties; sometimes they combine them with other substances to reduce the toxicity. Other chimpanzees eat flowers with antibiotic properties or leaves with antiparasitic ones, which act as laxatives or even induce uterine contractions. Chimpanzees also tear off bark and lick the resin to kill internal worms; the compounds, tests in vitro have shown, slow the growth of cancerous cells.

Significantly, practices of self-medication vary between chimpanzee populations. When chimpanzees feel sick, they seek out a particular tree and ingest a few leaves. The bitter leaves contain molecules that are quite effective against plasmodium parasites, which cause malaria. But chimpanzees also consume about ten other kinds of plant to combat these organisms. Thus, in contrast to human beings (who use a small number of substances for warding off malaria), chimpanzees diversify their medical arsenal. What’s more, when making their bed for the night, chimpazees in Uganda do so in areas where there are fewer mosquitos. Do they choose plants based on their potential for repelling pests, or is softness — and resulting comfort — decisive? We’ll see.

For some time now, chimpanzees’ pharmacopoeia has been the object of study. Indeed, research by Jane Goodall in the 1960s even prompted scientists to reexamine traits thought to be exclusively human. In fact, chimpanzees use an array of tools for different purposes: branches for digging out termites, honey, or marrow; sticks and stones for cracking nuts; and sharpened pieces of wood for spearing galagos (bushbabies); they even make “shoes” to protect their feet when climbing thorny trunks. Using these tools can be complex and require training; some mothers actively show their young the right way. Pedagogy, then, is a practice we share with chimpanzees. Another exciting finding: techniques differ from one population to the next (Uganda, Ivory Coast, Guinea, etc.). Many writers on the subject don’t hesitate to speak of “traditions” and “cultures.” This observation raises another set of questions. Do chimpanzees invent? In Tai National Park, Ivory Coast, generations of chimpanzees were known to use branches to break extremely hard nuts (dura laboriosa). One day, a female member of the group, Eureka, employed a stone for the same purpose and continued to do so in the presence of her companions. And then? Other chimpanzees started doing the same. After a few generations, the entire population had switched tools for cracking nuts, from sticks to stones.

Chimpanzees devise tools, but they’re even better at something else: memorization. The same chimpanzees in Ivory Coast have a geometrical understanding of their territory, which spans twenty-five square kilometers; they move from one spot to another in straight lines, more or less. Even with a limited range of vision — thirty meters, at most — they know where to go to find ripe fruit and avoid danger (including rival chimpanzees!). By remembering topographical features of the landscape and picturing abstract space, they can calculate distance and direction, no matter where they are.

This article is excerpted from Emmanuelle Pouydebat’s book “Atlas of Poetic Zoology.”

And that’s not the only proof of chimpanzees’ cognitive abilities. In a computer-based test of spatial memory, researchers compared young chimpanzees and university students. The experiment involved clicking numbers one by one, in the right order. At an ulterior stage, the task became more complicated: as soon as subjects clicked the first number, a white square blanked out the other ones; the point was still to press the right series, in order to receive a reward. And the results? The chimpanzees pulled it off 80 percent of the time — that is, twice as often as the students. From an early age, these animals demonstrate highly developed visual memory; it’s almost photographic. This is what enables them to memorize where the best fruit is growing and determine the best path to take. Whenever they don’t prefer to break our cameras, instead — or throw all kinds of stuff at us.

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