Researchers tested the teeth of early human ancestors found in Ethiopia using isotope analysis. The tests show us what these early humans ate because their teeth still contain chemical traces of the food sources. 

It turns out human ancestors switched to a proto-paleo diet 400,000 years earlier than previously thought – at about 3.8 million-years-ago.

Cleveland Museum of Natural History curator Yohannes Haile-Selassie is one of the authors of the study.

He says as the climate changed in Africa early humans adapted to eating newer drought resistant plants and the animals that lived off them:

“And we became much more generalists who could actually consume whatever was available and that’s what allowed this lineage of ours to thrive in different and varying habitats.”

He says other human-like primates that couldn’t adapt, went extinct. The study was published Monday in the Proceedings of the National Academy of Sciences.