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23
06, 2015
Early European Had Close Neanderthal Ancestor According to New Study
Early Modern European Humans Interbred with Neanderthals
The very last of the Neanderthals may have died out some 28,000 years ago but their legacy lives on as the modern human genome (Homo sapiens) contains traces of Neanderthal genetic material. The Neanderthals (Homo neanderthalensis) are the closest related species to our own, we share a common ancestor but this fact alone does not account for the one to three percent contribution to the genome of Eurasians, scientists believe that some time in the recent past these two species interbred. It seems that interbreeding between these two related species may have taken place much more recently than previously thought.
A new scientific paper published in the journal “Nature” reports on the study of an ancient human jawbone, this research suggests that interbreeding took place as recently as some 40,000 years ago.
The Ancient Human Jawbone Used in the Genetic Study
DNA analysis reveals a very recent Neanderthal ancestor.
Picture credit: Max Planck Institute for Evolutionary Anthropology/Svante Pääbo
Robust Human Jawbone
A robust human mandible was discovered in a cave system close to the town of Anina in south-western Romania back in 2002. The cave contains a huge amount of mammal bones including large numbers of Cave Bears (Ursus spelaeus) which probably used one of the chambers in the cave system as a hibernation den. The explorers found that a number of bones had been placed on nearby rocks, this suggested human activity and sure enough, the remains of early modern humans were found. A beautifully preserved human jawbone (mandible) and part of a skull were discovered.
Radiocarbon dating estimates that the jawbone is around 37,800 years old, making these fossil materials the oldest modern human bones to have been found in Europe. The cave, was called the “Peștera cu Oase”, which translates from the Romanian to mean “the cave of bones”.
Even if more conservative dating methods are used, the human remains come out at between 37,000 and 42,000 years old. The jaw is definitely H. sapiens as it shows a number of modern human morphologies including a prominent chin. However, a genetic analysis carried out by an international team of researchers which included scientists from Harvard Medical School, the Max Planck Institute of Evolutionary Anthropology and the Chinese Academy of Sciences, indicates that between six to nine percent of this person’s genome originates from Neanderthals. This is far greater than any other human sequenced to date.
Neanderthal Ancestor
As large segments of this individual’s chromosomes are Neanderthal in origin, it suggests that a Neanderthal was among this person’s most recent ancestors, perhaps just four to six generations back in this Romanian’s family tree. This new study provides substantial evidence that the first modern humans that arrived in Europe interbred with local Neanderthals.
Put simply, the person whose jawbone was found in the cave may have had a Neanderthal great grandparent!
A Researcher Carefully Extracts Fragments of Bone for the DNA Analysis
For their analysis the researchers used 35 milligrams of bone powder from the jawbone.
Picture credit: Max Planck Institute for Evolutionary Anthropology/Svante Pääbo
Homo sapiens bred with Homo neanderthalensis
A previous study had suggested that early modern humans migrating out of Africa mixed with Neanderthals in the Middle East between 50,000 and 60,000 years ago. Modern humans spread eastwards into Asia and westwards into Europe. Eventually, it was our species that spread to all parts of the world, the last of the Neanderthals dying out around 28,000 years ago.
One of the lead authors of the report Qiaomei Fu (Chinese Academy of Sciences), stated:
“The data from the jawbone imply that humans mixed with Neanderthals not just in the Middle East but in Europe as well.”
Svante Pääbo (Max Planck Institute for Evolutionary Anthropology), added:
“It is such a lucky and unexpected thing to get DNA from a human who was so closely related to a Neanderthal.”
Removing the Contaminating DNA
The research team had to very carefully sift out all the contaminating DNA before being able to assess the presence of remnants of Neanderthal genetic material. Most of the contamination was caused by microbial DNA in contact with the bone whilst it was in the cave, most of the hominin DNA recorded came from researchers who had handled the fossil bone.
Only a very tiny proportion of the genetic material analysed could be traced back to its Neanderthal origins.
The robust jaw and teeth do show some Neanderthal morphologies, this is to be expected given the close relatedness of this person to H. neanderthalensis. The scientists hope to continue their studies and identify more Neanderthal genetic material from ancient human remains. This will help them map potential Neanderthal/human interactions across Europe and Asia.
