Anthropology professor Mitch Irwin participated in international research that shed light on primate lifespans.

Irwin and his wife, biology professor Karen Samonds, have spent the last 14 years studying lemurs in Madagascar, according to NIU Today.

Their research was combined with the study of more than 17 other species of primate and published in the “Proceedings of the National Academy of Sciences.”

The research concluded that the primates that were studied burn half as many calories a day compared to other mammals, leading to a slower metabolism.

These results suggest there is a connection between slower metabolisms and lifespan among primates, including humans, according to NIU Today.