Humans helped kill off Neanderthals with STDs and other diseases, study shows

Research published earlier this year suggested that Neanderthal genes might have boosted our immunity and given us allergies, and now new research suggests that we may have returned the favor by infecting them with diseases we transported from Africa to Europe.

In the new study, which was published in the American Journal of Physical Anthropology this weekend, researchers from University of Cambridge and Oxford Brookes University reported that Neanderthals throughout Europe may have been infected by diseases that were brought there by Homo sapiens, and that said diseases may have contributed to their eventual demise.

Since both species were hominids, the researchers explained, it would have been easier for these pathogens make the jump from one species to another. Infections passed from modern humans to Neanderthals could have included tapeworm, tuberculosis, stomach ulcers, and herpes – all of which are chronic conditions that would have weakened the Neanderthals and made them less able to find food, thus harming the overall fitness of the species.

“Humans migrating out of Africa would have been a significant reservoir of tropical diseases,” Dr. Charlotte Houldcroft with the Cambridge Division of Biological Anthropology said Sunday in a statement. “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.”

Research suggests that disease transmission predates agriculture

Dr. Houldcroft and her colleagues reviewed evidence from recent research into the genomes of various pathogens and DNA from ancient skeletal remains, and found that some of the pathogens that currently affect humans could be several thousand years older than previously believed.

As genomic analysis has confirmed that modern human ancestors interbred with Neanderthals and that the two species exchanged genes associated with diseases, and in light of evidence that viruses moved into humans from other hominins while still in Africa, the study authors believe that it is safe to assume that Homo sapiens could – and probably did – pass diseases onto their ancient relatives.

“However, it is unlikely to have been similar to Columbus bringing disease into America and decimating native populations,” explained Dr. Houldcroft. “It’s more likely that small bands of Neanderthals each had their own infection disasters, weakening the group and tipping the balance against survival.”

She and co-author Dr. Simon Underdown, a researcher in human evolution from Oxford Brookes University, reported in their study that several infectious diseases may have been evolving along with humans and other hominids for at least tens of thousands of years. This would run contrary to the long-held view that infectious diseases exploded about 8,000 years ago, when agriculture began to supplant the hunter-gatherer way of life.

The researchers believe that diseases actually pre-date agriculture, and that many diseases that have long been thought to have originated in herd animals (including tuberculosis) actually had been originally transmitted to those creatures by humans. While Dr. Houldcroft and Underdown said that they have yet to find any concrete evidence of infectious disease transmission between humans and Neanderthals, they are convinced that, based on the overlap of time and geography and the evidence of interbreeding, that such transmission most likely took place.

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Image credit: University of Utah

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