By CrowdScience – BBC World Service

Something strange happened 35 years ago, when primatologist Mike Huffman was studying a group of chimpanzees in western Tanzania.

Chausiku, one of the females, left her young baby with other animals of the species, climbed a tree and lay down in a nest.

“It is unusual for chimpanzees to sleep during the day,” explains Huffman.

Then something extraordinary happened.

Chausiku came down from the tree, picked up his son, walked slowly and with difficulty, followed by the group, until she sat down in front of a bush.

“The name of the bush is mjonso,” explained Mohamedi Seifu Kalunde, Huffman’s research assistant.

Kalunde is a renowned expert in the local jungle. He was trained by his parents and grandparents in the art of herbal medicine, the study of medicinal plants. “It is a very powerful and important medicine for us,” he says.

Listen to Mike Huffman’s full podcast at https://www.bbc.co.uk/sounds/play/w3cszv77