Despite our advances in technology and medicine, we seem to be fighting a never-ending battle against a number of diseases and ailments. As viruses become more complex and bacteria become resistant to antibiotics, it seems that the lab-made drugs we have become so dependent on may no longer provide the cures we need. Perhaps this is why we are now turning to nature  in the hope that there may be a remedy tucked away somewhere in a remote tropical rain forest.
It could be that our closest living relatives, non-human primates, hold some of the answers we seek. Many species including chimpanzees make use of the natural resources in their habitats to self-medicate and improve their own health. This behaviour, known as zoopharmacognosy, typically involves ingestion or topical application of plants, soils, insects or even psychoactive drugs in order to treat and prevent diseases .
One of the most well known examples are domestic dogs and cats eating grass in order to induce vomiting if they have an upset stomach or internal parasite. However, most studies of animal self-medication are in non-human primates. One of the first documented cases was in 1983, when researchers observed chimpanzees in Tanzania folding and swallowing Aspilia spp leaves  without chewing them. Other scientists noted the same behaviour  in chimp colonies in Uganda and Nigeria. This is quite unusual, not only because there is no nutritional benefit in swallowing these leaves whole, but also because the leaves themselves have a rough and bristly surface. So what is the purpose of doing this?