Human Diseases Spelled Doom For Neanderthals

Homo sapiens passed on tropical diseases, ringworm, tuberculosis, tapeworms and stomach ulcers to Neanderthals, which may have contributed to the latter's extinction, according to recent reports. In the past few years, researchers have found that humans and Neanderthals interacted more closely than previously thought, and inter-species mating also took place.

As per a study published in the American Journal of Physical Anthropology, Homo sapiens shifting from Africa to Europe, a Neanderthal stronghold, passed along human 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," said Charlotte Houldcroft from the Biological Anthropology division of Cambridge University.

Earlier, it was assumed that the development of agriculture led to the evolution of numerous infectious diseases, owing to the close contact between humans and domestic animals. Recent studies, however, suggest that infectious disease genomes developed thousands of years earlier than previously estimated. In fact, the timeline can extend by millions of years too. Though scholars have found no direct evidence linking transmission of diseases between Homo sapiens and Neanderthals, the new timelines for the diseases could imply that there may be high chances of humans carrying them while migrating to Neanderthal land.

Researchers earlier thought that the stomach ulcer causing the bug, Heliobacter pylori, made its appearance 8000 years ago, at the onset of agriculture. However, a study of the bug's genome revealed it to be at least 88,000 years old. The study of Herpes Simplex 2, the virus that causes genital herpes, showed it was transmitted to Homo sapiens about 1.2 million years ago from an unknown hominid.

It has, however, been noted that unlike the instance of diseases transferring from Europeans to Native Americans, that caused colossal epidemics like small pox and killed millions in a short duration of time, the transfer of disease between humans and Neanderthals was a more localized phenomenon. Neanderthal Hunter-gatherers lived in small groups of 15 to 30; therefore, infectious diseases could probably affect only one isolated group at a time. Research suggests that cumulative factors over thousands of years, that may include death by human diseases, led to the extinction of Neanderthals.