The deliberate ingestion of soil, or geophagy, has important health benefits for chimpanzees, according to Sabrina Krief and her colleagues from the Musum National dHistoire Naturelle in Paris, France. Far from being a dysfunctional behavior, geophagy has evolved as a practice for maintaining health amongst chimpanzees. In this particular study (1), to be published online this week in Springers journal Naturwissenschaften, geophagy increases the potency of ingested plants with anti-malarial properties.
Although geophagy is widespread throughout the animal kingdom, in humans it is perceived as a curious behavior, even linked by some to mental health issues. The paper looks at the consequences of soil ingestion on the health status of chimpanzees in the Kibale National Park in Uganda. These chimpanzees have been observed to ingest soil shortly before or after consuming plant parts, such as the leaves of Trichilia rubescens, which have anti-malarial properties in the laboratory.
The research team collected fourteen samples of soil eaten by chimpanzees as well as T. rubescens leaves from young trees in the same area. They designed a digestion model to replicate the digestive process of mastication, gastric and intestinal digestion in the laboratory. The samples were then analyzed for bioactive properties. The soil and leaves were examined both individually and as a mixture.
Before being mixed with the soil, the digested leaves showed no significant anti-malarial activity. However, when the leaves and soil were digested together, the mixture had clear anti-malarial properties.
The researchers also compared the composition of the soil eaten by chimpanzees with the content of soil used by the local healer to treat diarrhea amongst his patients. All the soil samples were rich in the clay mineral kaolinite, the principal component of some anti-diarrheal medicines. Furthermore, samples used by chimps and humans had exactly th
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