An extensive look at what chimpanzees consume each day reveals that many of the plants they consume aren't for nutrition but are likely ingested for medicinal purpose.
The findings, published in the journal Physiology & Behavior, indicate that the origins of medicine go way back, beyond the human species.
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"We conclude that self-medication may have appeared in our ancestors in association with high social tolerance and lack of herbivorous gut specialization," lead author Shelly Masi and her colleagues write.
Masi, a researcher at the National Museum of Natural History in Paris, and her team recorded the items consumed by a community of over 40 wild chimpanzees at Kibale National Park, Uganda. They also documented the availability of the foods, as well as the social interactions between the chimps.
They also documented the same information for about a dozen wild western gorillas in Dzanga-Ndoki National Park, Central African Republic.
Unusual food consumption in chimpanzees, meaning foods not normally associated with nutritional needs, was twice as high as it was for gorillas. Gorillas turn out to have more specialized guts that are better capable of detoxyifying harmful compounds, making them have have less of a need to self-medicate than chimps and humans may need to.
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Chimpanzees and people are extremely social and both learn from each other, including what to eat.
"Older and more successful individuals (such as those that are high ranking) are expected to be the best model to copy, and are mainly responsible for generating and transmitting food traditions," according to the authors.
Analysis of the mostly non-nutritional and sometimes slightly toxic foods consumed determined that most had medicinal properties. Based on the study, the chimpanzee medicine chest appears to include the following: Antiaris toxicaria leaves (anti-tumor), Cordia abyssinica pith (anti-malarial and anti-bacterial), Ficus capensis (anti-bacterial), Ficus natalensis bark (anti-diarrheal), Ficus urceolaris leaves (de-worming agent), and many more.
The primates seemed to strategically go for the medicinal parts of these plants, and would consume them even when other more nutritious and palatable foods were available.
While chimps and humans appear to be the world's most self-medicating animals, another new study, accepted for publication in the journal Small Ruminant Research, documents how both wild and domesticated herbivores also consume plants for medical reasons.
Juan Villalba of Utah State University's Department of Wildland Resources, and co-author Serge Landau of Israel’s Volcani Center explain how goats sometimes nibble on the anti-parasitic plant Albizia anthelmintica. This was "followed by expulsion of worms in the feces and alleviation" of the worm problem.
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Stacy Lindshield, an Iowa State University researcher, also identified a medicated body scratcher invented by wild spider monkeys.
"Spider monkeys have been observed rubbing crushed and chewed leaves on their bodies," Lindshield told Discovery News, explaining that "some primates select plants or invertebrates with chemical properties." In addition to medicinal purposes, she said the resulting smelly ointment might also facilitate olfactory communication.
Julio Mercader, a University of Calgary archaeologist, told Discovery News that he believes such medicinal and otherwise useful plant “tools” merit study via a new interdisciplinary field of primate archaeology.
He said, "We used to think that culture and, above anything else, technology was the exclusive domain of humans, but this is not the case."