Humans invaded rainforests at least 20,000 years ago: Teeth found in Sri Lanka reveal tropical diet of our ancestors

They are some of the richest habitats on the planet yet also the hardest for humans to inhabit.
Now scientists have discovered that humans may have first begun living in the rainforest around 20,000 years ago – 12,000 years earlier than was thought.

Researchers at Oxford University found the evidence trapped inside human teeth discovered in the rainforests of Sabaragamuwa in southern Sri Lanka.

The study also notes that there are hints that humans may even have occupied rainforests around 45,000 years ago.
The findings contradict the idea that tropical rainforests were largely human-free environments until around 8,000 years ago.

Professor Julia Lee-Thorp, an archaeologist at Oxford University who helped lead the study, said: ‘The isotopic methodology applied in our study has already been successfully used to study how primates, including African great apes, adapt to their forest environment.

‘However, this is the first time scientists have investigated ancient human fossils in a tropical forest context to see how our earliest ancestors survived in such a habitat.’

The researchers, whose work is published in the journal Science, studied the fossilised teeth of 26 humans of a range of dates – from 20,000 to 3,000 years ago – found around Sri Lanka.
The areas where they were excavated from are all now dense rainforest but it was not clear what the landscape was like when the people were alive.

By examining the carbon and oxygen isotopes in the teeth, the researchers were able to see that the humans had a diet that matched those of people living in slightly open ‘intermediate rainforest’ environments.

Patrick Roberts, an archaeology student at Oxford University and lead author of the study, said: ‘This is the first study to directly test how much early human forest foragers depended on the rainforest for their diet.

‘The results are significant in showing that early humans in Sri Lanka were able to live almost entirely on food found in the rainforest without the need to move into other environments.

‘Our earliest human ancestors were clearly able to successfully adapt to different extreme environments.’
Professor Mike Petraglia, who also took part in the study at Oxford University, added: ‘Our research provides a clear timeline showing the deep level of interaction that early humans had with the rainforest in South Asia.

‘We need further research to see if this pattern was also followed in other similar environments in Southeast Asia, Melanesia, Australasia and Africa.’