Although we know the HIV epidemic began in the 1980s and its origins go back to early 1900s Africa, researchers now believe that HIV-related retroviruses can be traced as far back as 60 million years, according to research led by Daniel Elleder of the Czech Academy of Sciences and published in Molecular Biology and Evolution.

HIV is a type of lentivirus—a virus with a long incubation period that causes a variety of chronic illnesses in mammals. According to a press release on the study, until Elleder’s findings, the oldest known lineages of lentiviruses had been traced back between 3 million and 12 million years. They were found in lemurs, rabbits and ferrets.

Elleder and his team looked at ancient genetic samples of Malayan flying lemurs, from which they sequenced lentivirus remnants and reconstructed viral genomes. The results mean that the oldest lentiviruses could have emerged as long as 60 million years ago.

Why does this matter in 2016?

“We hope that our findings will allow virologists to better understand how lentiviruses evolved and how their hosts developed defenses against them,” Elleder said in the press release.

In other words, the more pieces to this puzzle that we understand, the better our chances of fighting modern lentiviruses like HIV.