Scientists know that Neanderthals went extinct around 40,000 years ago, but they have struggled to understand why we survived and they didn’t. But thanks to a recent study of viruses in Neanderthals, they may finally have their answer.

But make no mistake, Neanderthals and humans are not the same. Neanderthals looked slightly similar to ancient humans, but their DNA was distinctly different.

They don’t know exactly how intertwined their lives were, but they do know that the two species would occasionally cross paths, spend time together, and even mate. But, somehow, every last Neanderthal died about 40,000 years ago while humans continued to thrive. 

Several theories have been presented over the past few decades, but none have been proven because scientists lack any physical evidence.

Additionally, some say humans were simply smarter and used weapons to defeat the less intelligent species.

From competing with a rival species to surviving a cold front or even fighting against humans, if Neanderthals were struggling to stay healthy, they could never have survived. 

A team of researchers studied the DNA of two Neanderthals, one adult and one child male, from the Chagyrskaya Cave in what is now Southern Siberia, specifically looking for the residue of viruses. And they found three different ones: adenovirus, herpesvirus, and papillomavirus.

Adenoviruses cause respiratory infections, such as the common cold and flu. Herpesviruses cause genital warts or cold sores, and papillomaviruses can cause certain cancers, including cervical cancer.

Additionally, many scientists believe that it proves the hypothesis that poor health was at least a part of the reason why Neanderthals went extinct. As Marcelo Briones, a co-author of the study, explained, “A cold does not have to be fatal to decrease hunting efficiency or reproductive ability.”

Some say that it’s likely because humans’ immune systems were stronger than those of their Neanderthal cousins. However, it’s almost impossible to say for sure. 

In fact, some scientists have all but dismissed the study, saying that a great deal more research would need to be conducted before they can finalize this theory. However, finding viruses in Neanderthals is certainly still exciting, even if it doesn’t prove the extinction theory.

Tasha Tabachnikova, a PhD candidate studying herpesvirus at Yale School of Medicine, explained, “[Viruses] have a huge impact on human health because they are long-lived infections.” Any additional information could improve how we treat and vaccinate against these often deadly diseases.