Monkeys, the first doctors! - Part 2

In 1987, Prof Michael Huffman happened to be watching a constipated chimpanzee called Chausiku in the dense rainforest of the Mahale mountains in western Tanzania.By seeing a noxious tree shoot that chimps would normally avoid, Chausiku peeled it and sucked its bitter pith. Within a day, her constipation was gone. It was the first time a scientist had seen a sick chimp select an unsavoury plant known by humans to have medicinal properties, and then recover.

 The pith, from the tree Vernonia amygdalina, has now given up its secrets. It contains compounds active against many of the parasites responsible for malaria, dysentery and schistosomiasis. Prof Huffman has found that nearly all of the ape remedies he has studied are also used by local people as medicine.

For more evidence, take a remarkable type of self-medication first seen among chimpanzees in Tanzania. Jane Goodall, the veteran ape watcher, spotted chimps swallowing leaves .What is remarkable is that leaf-swallowing of the chimps increases in many sites about two months after the rainy season has begun - about the same time as the peak of infection with Oesophagostomum stephanostomum, a nodular worm which is linked with bacterial infection, diarrhoea, severe stomach pain, weight loss, and weakness, resulting in high mortality. Later those leaves found to have some antidiarrhoeal properties.

Prof Huffman has shown that individual leaves from any of 34 different plants are swallowed whole by chimpanzees, bonobos and gorillas across Africa - but that it tends to be only the sick chimps that will swallow leaves, and that they do so on an empty stomach. He tested the fresh dengs of these animals and could find leaf particles with various medicinal properties.

But self-medication is not confined to chimps. At Bwindi Impenetrable Park and Mgahinga National Park in Uganda, mountain gorillas chew the bark of the nondescript Dombeya tree as a food.The bark is laden with active ingredients, including antibiotics that kill common bacteria such as E. coli, and there is anecdotal evidence that the presence of bugs in gorilla dung matches the ape's Dombeya-eating patterns. In southern Mexico, howler monkeys eat figs that can fight parasite infections.

It is not just curative medicine that was invented by our animal relatives, but preventative, too. Baboons living near the city of Taif, Saudia Arabia, are known to dig drinking holes in the sand directly adjacent to the algae-tainted watering sites of livestock.To ensure the water does not make them sick, they patiently wait for the filtered water to seep through the sand.