Ancestors of Europeans and Asians, through interbreeding with Neanderthals about 50,000 years ago, resulted in a genetic “gift” that keeps on giving with humans today (non-African) being made up of about 1% to 2% of neanderthal DNA.
Go ahead and call your friend a neanderthal, there is some truth to it
Researchers believe that the two-way gene exchange and the fact that non-African humans could even suffer from depression and certain allergies owing to this neanderthal DNA.
According to a study published in Nature today, this gene exchange likely occurred in Siberia about 100,000 years ago which is odd. Scientists have largely postulated that the migration of what would now be ancestors of non-Africans only began about 50,000 to 60,000 years ago. This dating suggests that Neanderthals got their DNA give from an early migration of humans that to this day remains a mystery.
“I think at this point we’ve convinced everybody the observation is real,” said Adam Siepel, a geneticist at Cold Spring Harbor Laboratory and a co-author of the new study. “But the story behind the observation is still very much in dispute.”
In 2010, scientists at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, were able to construct about 60% of the Neanderthal genome from fossil remains found in a cave in Croatia. The recovery of the genome showed that Europeans and Asians share some Neanderthal genetic mutations but that Africans do not.
Fast forward to 2013, where the same team compiled the complete genome of a Neanderthal from a 50,000 year-old toe bone discovered in the Altai Mountains of Siberia.
By comparing this complete genome to our (modern) DNA allowed the team to confirm the aforementioned interbreeding.
Now lets compare Neanderthals
Sergi Castellano, a geneticist at Max Planck Institute was joined by Dr. Siepel and their colleagues to determine how isolated populations of Neanderthals were from one another. And true to form, the two along with the other researchers, using statistical models, determined that Neanderthal DNA did transfer to modern Asians and Europeans.
However, that was not all they found. The team discovered that the Altai Neanderthals shared DNA with living Africans but not Asians and Europeans. This suggested that an African lineage of humans bred with the ancestors of the Altai Neanderthal before the split of the Neanderthal population. Something that didn’t jibe with past migration theories and caused the team to believe they had made a big error, but they hadn’t.
“We poked and prodded and poked and prodded, and couldn’t get it to go away,” said Dr. Siepel.
While they checked and rechecked, they still couldn’t explain how these genes would have passed about 100,000 years ago. Another co-author of the study, Bence Viola, a paleontologist at the University of Toronto expressed his skepticism, “It’s really weird, that’s my main impression.”
While it took some doing, Dr. Castellano finally convinced Dr. Viola that his data was spot on much to the consternation of the latter.
In the 1930’s, scientists found 120,000-year old fossils in the Middle East that approached the appearance of today’s humans leading many to believe that a failed migration from Africa may have occurred earlier than once thought.
Last year, Chinese scientists found nearly 50 teeth (again in a cave, always a cave) they estimate to be between 80,000 and 120,000 years old that belong to modern humans, though Dr. Viola doubts this find. He postulates that humans expanded into the Middle East and there interbred with Neanderthals. From there the Neanderthals found their way to Siberia.
“There’s going to be a lot more data really soon,” said Jonathan K. Pritchard, a geneticist at Stanford University who was not involved in the study. “I would expect in the next few years we’ll have much, much more of the jigsaw puzzle, and it will be possible to piece this all together.”