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Neanderthals and modern H. sapiens crossbred over 100,000 years ago

There were at least two cases of cross-breeding between both species

Spanish National Research Council (CSIC)

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IMAGE: Over 100,000 years ago, anatomically modern humans ventured out of Africa for the first time. view more

Credit: IVAN HEREDIA / CSIC

A multidisciplinary team which included participants from the Spanish National Research Council (CSIC) has discovered that Homo neanderthalensis and Homo sapiens crossbred over 100,000 years ago. This puts back the previously first-known case of a hybrid produced by the two species by 50,000 years. This earlier genetic exchange, which may have taken place in the Near East, has not been detected in European Neanderthals. The results of the work appear in the latest edition of 'Nature' magazine.

A multidisciplinary team which included participants from the Spanish National Research Council (CSIC) has discovered that Homo neanderthalensis and Homo sapiens crossbred over 100,000 years ago. This puts back the previously first-known case of a hybrid produced by the two species by 50,000 years. This earlier genetic exchange, which may have taken place in the Near East, has not been detected in European Neanderthals. The results of the work appear in the latest edition of Nature magazine.

Analysed the genomes of a Neanderthal and a Siberian Denisovan, as well as the sequences of chromosome 21 of a Neanderthal found in the 'Sidrón' cave in Asturias, Northern Spain, and of another from Vindija, Croatia.

The CSIC researchers who took part in the study were Carles Lalueza-Fox (Institute of Evolutionary Biology) and Antonio Rosas (Spanish Natural Science Museum). Others who took part were the archaeologist, Marco de la Rasilla, along with other specialists in genomics, Tomás Marques-Bonet and Sergi Castellano, the latter being jointly responsible for the study.

Rosas explains that the work poses a brand new scenario. "Over 100,000 years ago, anatomically modern humans ventured out of Africa for the first time. These modern humans met and interbred with a group of Neanderthals, which later may have moved to the south of modern day Siberia, carrying the genes of H. sapiens."

What researchers have known since 2010, thanks to the study of the Neanderthal genome, is that around 50,000 years ago, following their migration from Africa, a group of modern humans- the predecessors of today's Europeans and Asians- interbred with Neanderthals. As a consequence of this gene flow, these non-African modern humans carry 2% genetic sequences from Neanderthals. In contrast, the Sub-Saharan modern human population, who never had any contact with Neanderthals, therefore do not carry this ancient gene (apart from very recent introgression).

Do all Neanderthals have H. sapiens DNA?

This history-making new research has discovered, therefore, that modern humans also passed their genes to the Neanderthal population. H. sapiens and Neanderthals cross-bred on at least two separate occasions, 100,000 years ago and 50,000 years ago.

The research analysed Neanderthal fossil remains from geographically distant European locations. "The sequences of chromosome-21 of (Neanderthal) remains found in the Sidrón cave in Asturias, Northern Spain, and in another cave in Vindija, in Croatia found that European Neanderthals did not have- in this chromosome at least- H. sapiens genes. In other words, perhaps these Neanderthal groups did not coincide with H. sapiens, or, if they did, they did not have any offspring" says CSIC researcher, Carles Lalueza.

The first migration from Africa

According to Rosas, "These discoveries have direct implications on the evolutionary model." For decades we have known that there was an early migration of H. sapiens out of Africa, because of the remains that were found at the archaeological sites at Skhul and Qafzeh in Israel. But without palaeontological data, this movement was seen as a failed attempt at migration, since it went no farther than the Near East.

The information presented now seems to coincide with recent archeo-paleontological evidence. Such as the recent announcement on the presence of Homo sapiens in China around 100,000 years ago. Likewise, stone tools found in the south of the Arabian Peninsula have been attributed to this early H. sapiens journey out of Africa. Both pieces of evidence could well tie in with those modern humans who passed their genes on to the branch of Neanderthals who migrated East.

According to the researchers, following the results of this latest study, the meaning behind -and the geographical reach of- the first H. sapiens to leave Africa has yet to be analysed, as does the extent to which this exodus contributed to today's genetic diversity.

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