Increasingly, scientists are becoming aware that our conceptions of human-Neanderthal relations during the time the two species shared the Earth were not as accurate as once thought. Advances in genetic analysis have led to new understandings of the interactions between the two species, and the overwhelming consensus is that they knew each other long before scientists initially estimated.

According to a report from Smithsonian Magazine, a recent study adds to our understanding of the relationship between early humans and Neanderthals with the revelation that humans were likely responsible for spreading a number of diseases to our ancient hominid cousins.

The study suggests that the mass migrations of early Homo sapiens from Africa into European regions facilitated the transmission of a number of nasty diseases including herpes, tuberculosis, tapeworms, and stomach ulcers to Neanderthal populations.

According to the study’s head author, Charlotte Houldcroft from Cambridge University’s Division of Biological Anthropology, “Humans migrating out of Africa would have been a significant reservoir of tropical diseases. For the Neanderthal population of Eurasia, adapted to that geographical infectious disease environment, exposure to new pathogens carried out of Africa may have been catastrophic.”

Previously, many scientists believed the proliferation of infectious diseases didn’t begin until well after the development of agriculture, which resulted in more and more people living together in tight quarters and coming into contact with domesticated animals.

But genetic analysis reveals that this is far from the case. Analysis of Herpes Simplex 2, the bug that causes genital herpes, reveals that the disease was transmitted more than 1.2 million years ago.

“Our hypothesis is basically that each band of Neanderthals had its own personal disaster and over time you lose more and more groups,” says Dr. Houldcroft. “I don’t think we’ll ever find a single theory of what killed the Neanderthals, but there is increasing evidence that lots of things happened over a period of a few thousand years that cumulatively killed them off.”

The study, published in the American Journal of Physical Anthropology, can be found here.