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DNA reveals Neanderthal extinction clues

Neanderthals were already on the verge of extinction in Europe by the time modern humans arrived on the scene, a study suggests.

DNA analysis suggests most Neanderthals in western Europe died out as early as 50,000 years ago - thousands of years before our own species appeared.

A small group of Neanderthals then recolonised parts of Europe, surviving for 10,000 years before vanishing.

The work is published in the journal Molecular Biology and Evolution.

An international team of researchers studied the variation, or diversity, in mitochondrial DNA extracted from the bones of 13 Neanderthals.

This type of genetic information is passed down on the maternal line; because cells contain multiple copies of the mitochondrial genome, this DNA is easier to extract from ancient remains than the DNA found in the nuclei of cells.

The fossil specimens came from Europe and Asia and span a time period ranging from 100,000 years ago to about 35,000 years ago.

The scientists found that west European fossils with ages older than 48,000 years, along with Neanderthal specimens from Asia, showed considerable genetic variation.

But specimens from western Europe younger than 48,000 years showed much less genetic diversity (a six-fold reduction in variation compared to the older remains and the Asian Neanderthals).

In their scientific paper, the scientists propose that some event - possibly changes in the climate - caused Neanderthal populations in the West to crash around 50,000 years ago. But populations may have survived in warmer southern refuges, allowing the later re-expansion.

Low genetic variation can make a species less resilient to changes in its environment, and place it at increased risk of extinction.

"The fact that Neanderthals in Europe were nearly extinct, but then recovered, and that all this took place long before they came into contact with modern humans, came as a complete surprise," said lead author Love Dalen, from the Swedish Museum of Natural History in Stockholm.

"This indicates that the Neanderthals may have been more sensitive to the dramatic climate changes that took place in the last Ice Age than was previously thought."

Neanderthals were close evolutionary cousins of modern humans, and once inhabited Europe, the Middle East and Central Asia. The reasons behind their demise remain the subject of debate.

The appearance of modern humans in Europe around the time of the Neanderthal extinction offers circumstantial evidence that Homo sapiens played a role. But changes in the climate and other factors may have been important contributors.

"The amount of genetic variation in geologically older Neanderthals as well as in Asian Neandertals was just as great as in modern humans as a species," said co-author Anders Gotherstrom, from Uppsala University.

"The variation among later European Neanderthals was not even as high as that of modern humans in Iceland."

The researchers note that the loss of genetic diversity in west European Neanderthals coincided with a climatic episode known as Marine Isotope Stage Three, which was characterised by several brief periods of freezing temperatures.

These cold periods are thought to have been caused by a disturbance of oceanic currents in the North Atlantic, and it is possible that they had a particularly strong impact on the environment in western Europe, note the researchers.

Over the last few decades, research has shown that Neanderthals were undeserving of their brutish reputation.

Researchers recently announced that paintings of seals found in caves at Nerja, southern Spain, might date to 42,000 years - potentially making them the only known art created by Neanderthals. However, this interpretation remains controversial.

By Paul Rincon Science editor, BBC News website 27/2/12

Régine Zylberberg by jupiter869

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Replies to This Discussion

Permalink Reply by Joan Denoo on March 30, 2012 at 2:10am

This kind of research fascinates me. To be able to track the migration out of Africa, put time scale to the different migrations, and the interaction with Neanderthals captures my imagination. I played around a little bit in Mexico with the different linguistic groups that came into what is now Mexico/Texas, and learned how different pottery, foods, art, and those kinds of things help to understand history. But the thing that really enchants me is the realization we are all connected. We all evolved over time and space to have certain characteristic in common and some distinct differences. I enjoy these articles.

Permalink Reply by Napoleon Bonaparte on March 30, 2012 at 4:24am

You might like The Incredible Human Journery by Alice Roberts which is her story of how we colonised the planet.

The book was made into a television series which can be found on You Tube.

Permalink Reply by Napoleon Bonaparte on March 30, 2012 at 3:41pm

Dr. Alice Roberts (left) tells the story of our Incredible Human Journey from Africa to populate the world.

http://www.atheistnexus.org/video/dr-alice-roberts-the-incredible-h...

Dr. Alice Roberts presents her story of the Incredible Human Journey of our ancestors leaving Africa and populating the world. She retraces their steps in the direction of the rising sun in a 5-part series each being 1 hour episodes.

Permalink Reply by Steph S. on March 30, 2012 at 5:03pm

Is that a picture of Dr. Alice Roberts?

hehe

Permalink Reply by Tony Carroll on March 30, 2012 at 5:43pm

Yeah, that was kind of startling. Took me about 5 min. to get back to the post. Somehow uh, my computer froze. Yeah, that's it! It just quit. (LOL!!!!).

Permalink Reply by Steph S. on March 30, 2012 at 5:44pm

It's a good attention getter. Made me laugh. hehe

Permalink Reply by Napoleon Bonaparte on April 1, 2012 at 3:58am

It looks similar but I wasn't wearing my glasses at the time.

Permalink Reply by Nontheist Central on March 30, 2012 at 5:28pm

As George Takei would say "Oh myyy!" I don't think that's her. lol

Loved the Incredible Human Journey, though! Fantastic series!

Permalink Reply by Napoleon Bonaparte on March 31, 2012 at 4:48am

I remember George Takai from Star Trek but I didn't know he is an anglophile and likes all things British. He even likes British food. That's funny ! lol !

He has had a busy career as an actor so I'm off to Wikipedia and You Tube now.

Permalink Reply by Alex Barnham on April 2, 2012 at 9:34pm

As we can all plainly see, the DNA of this beautiful creation has allowed her (of course I say that because I can expect when she covers her mouth when she coughs, no doubt will linger) to not only survive, but to really enjoy her survival. From my experience, the best way to limit overpopulation is found at the end of our fingers. You could say that the end is at hand if we don't enjoy what we can do with our hands. Leaving all traditional taboos aside, the pleasures of existence are fully within our grasp, so to speak. I would say that humans are the masters of their fate if they could but learn to masturbate. Otherwise why would we have such beautiful organs.

Permalink Reply by Napoleon Bonaparte on April 18, 2012 at 9:12am