Neanderthals, a human subspecies, might have contracted tropical diseases from the humans migrating out of South Africa, leading to their end about 40,000 years ago, according to a new theory.
The earlier hypothesis for their supposed extinction, believed to be due to the spread of infectious diseases from livestock or owed to the agricultural explosion that happened 8,000 years ago, has been challenged by this new theory.
In a recent study, researchers from Cambridge and Oxford Brookes Universities have found genetic data indicating that many infectious diseases had been co-evolving with humans and our ancestors for tens of thousands to millions of years.
"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 ... 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." explained Dr. Charlotte Houldcroft, from Cambridge's division of biological anthropology. Houldcroft also studies modern infections at Great Ormond Street Hospital.
Potential evidence has been found supporting the probability that mating between the two species, Neanderthals and Homo sapiens, occurred. This in turn subsequently involved the transfer of genes associated with the diseases. There is also evidence pointing to the fact that the viruses were initially transmitted to the humans from other hominins in Africa through interbreeding.
Several infections that are likely to have been passed on to the Neanderthals from the humans include tuberculosis, tapeworm, stomach ulcers and types of herpes. These are all chronic diseases that might have weakened the Neanderthals' natural hunting skills, which invariably curbed their ability to find food, deteriorating their health. This in turn could have been responsible for the eventual extinction of the species.
Based on the latest evidence obtained from the review of pathogen genomes and DNA from ancient bones, it was concluded that some infectious diseases are thousands of years older than previously thought.
The paper has been published in the American Journal of Physical Anthropology.
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