A new study published on April 10 by the American Journal of Physical Anthropology suggests that Neanderthals in Europe could have been infected with several diseases, like tapeworm, tuberculosis, stomach ulcers and certain types of herpes, carried out by the modern human kind, the Homo sapiens from Africa, contributing to the extinction of the previous kind.
The anthropologists involved in this research, Charlotte Houldcroft, from Cambridge’s Division of Biological Anthropology, and Simon Underdown, a researcher in human evolution from Oxford Brookes University, found that since both were species of hominin, it was probably easier for diseases to be transmitted from on population to another.
“Humans migrating out of Africa would have been a significant reservoir of tropical diseases.” She also added: “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,” said Houldcroft.
The report, titled “Neanderthal genomics suggests a Pleistocene time frame for the first epidemiologic transition”, suggests that the Neanderthals had no natural immunity to these new diseases, which most likely led to their extinction 40,000 years ago.
The Neanderthal’s immune system
The researchers analyzed ancient DNA and pathogen genomes from fossilized bones, finding that Neanderthals carried genes that would protect them against bacterial blood poisoning or sepsis. Nonetheless, and since the species had no immunity, these infectious tropical diseases carried by the Homo sapiens may have weakened Neanderthal groups, leaving them vulnerable, when they began interacting and interbreeding, making them less fit and able to find food, which could have caused their extinction.
These infectious diseases are likely to be thousands of years older than people thought, and might have had a role in one of the most significant extinctions in human history. Houldcroft and Underdown said that they have been co-evolving with humans and our ancestors for tens of thousands to millions of years.
The diseases are considered different from the way smallpox wiped out the Native Americans when Columbus arrived in America. The researchers think that each small group of Neanderthals suffered their own infection, causing disasters within them and not making them able to survive.
Aside from the thought of these infectious diseases existing for a long time, it was also found that they expanded with the beginning of agriculture some 8,000 years ago, as the sedentary human populations coexisted with farm animals, creating a perfect atmosphere for the disease to spread.
“Hunter-gatherers lived in small foraging groups. Neanderthals lived in groups of between 15-30 members, for example. So disease would have broken out sporadically, but have been unable to spread very far. Once agriculture came along, these diseases had the perfect conditions to explode, but they were already around,” said the anthropologists.