Posted on 06/05/2006 1:11:24 PM PDT by PatrickHenry
By recovering and sequencing intact DNA from an especially ancient Neandertal specimen, researchers have found evidence suggesting that the genetic diversity among Neandertals was higher than previously thought. The findings also suggest that genetic diversity may have been higher in earlier Neandertal periods relative to later periods that approached the arrival of humans in Europe. Changes in genetic diversity over time are thought to reflect population events, such as low-population bottlenecks caused by disease or environmental change, as well as the influence of random genetic change. The findings are reported in the June 6th issue of Current Biology by a group of researchers including Ludovic Orlando and led by Catherine Hänni of Ecole Normale Supérieur in Lyon, France.
Neandertals were the only representatives of the genus Homo in Europe during most of the last 300,000 years, becoming extinct shortly after the arrival of modern humans on the continent around 30,000 years ago. Traces of mitochondrial DNA (mtDNA) sequences still present in fossilized bones have been used in past studies in an effort to identify and track the potential genetic legacy of Neandertals among modern Europeans. Though such genetic continuity would have been the hallmark of interbreeding between modern humans and Neandertals at the time of their European coexistence, the mtDNA sequences from the nine neandertal specimens that have been analyzed to date – and that lived around the time of the cohabitation period – do not match those found among modern humans, suggesting that little, if any, interbreeding took place.
In their new work, Dr. Hänni and colleagues now report the oldest Neandertal mtDNA sequence ever recovered. The Neandertal specimen analyzed consists in a molar of a 10-12 year-old child that lived in the Meuse valley (Scladina cave, Belgium) around 100,000 years ago. The specimen yielded 123bp of mtDNA – a very short section of DNA by modern sequencing standards, but a technical feat considering the very ancient source of tissue. The reason for choosing such an old specimen was simple: it unambiguously predates the period when Neandertals cohabited with modern humans. By comparing this sequence with already published – and considerably younger – Neandertal sequences, the researchers sought to reveal whether the Neandertal mtDNA pool exhibited long-term stability or drastic modification around the time of cohabitation with modern humans. There was a second reason to pay attention on the Scladina molar: it has only been discovered very recently. This means that all individuals who have been in contact with it are known, and their DNA could be sequenced to detect any possible contamination of the Neandertal sample by modern human DNA.
The Neandertal sequence from Scladina confirms that Neandertals and modern humans were only distant relatives – Neandertal sequences are all closer to each other than to any known human sequence. But the study also reveals that the genetic diversity of Neandertals has been underestimated. Indeed, the mtDNA from the Scladina sample is more divergent relative to modern humans than is mtDNA from recent Neandertals, suggesting that Neandertals were a more genetically diverse group than previously thought.
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Hmm ... this sound interesting. Thanks for the post. I will read it later.
"genetic diversity among Neandertals was higher than previously thought.."
So why are they extinct?
They were out-competed. Genetic diversity is no guarrantee of evolutionary success.
This could be explained if Neanderthal women were exceedingly unappealing, and the only interbreeding that took place was between Neanderthal men and HS women.
No Howard Dean jokes yet?
:)
Because Cain killed Abel ...
"Because Cain killed Abel ..."
Interesting. Are you suggesting a the Bible story is a metaphor for the actual event of Homo Sapiens killing off Neandertal?
Not sure it means they were all that diverse near the end of their walking-around time.
I think it refers more to the overall diversity across their entire era as it were. This sample was an early specimin. Indeed a bottleneck toward the end of their era might still have been a problem. Much like the present day cheetah story where they have almost no diversity among the immune response genes (and common cat viruses can wipe them out).
Maybe they will be able to squeeze a bit more out of that tooth in time. The techniques are improving very quickly.
Yes, just suggesting that it might be.
> So why are they extinct?
Compare a "diverse" group of street thugs against a non-diverse group of, say, all-white Navy SEALs or all-black Army Rangers or all-Innuit Delta Force.
Or a truckload of chihuahuas, pomeranians and other fishbait dogs against a pack of wolves.
Diversity does not necessarily mean strength. Nor does it mean weakness.
"Yes, just suggesting that it might be."
I had never heard that before. Very interesting.
Cain slew Abel Seth knew not why
For if the children of Israel were to multiply
Why must any of the children die?
So he asked the Lord
And the Lord said:
"Man means nothing he means less to me
than the lowiliest cactus flower
or the humblest yucca tree
he chases round this desert
cause he thinks that's where i'll be
that's why i love mankind
I recoil in horror from the foulness of thee
from the squalor and the filth and the misery
How we laugh up here in heaven at the prayers you offer me
That's why i love mankind"
The Christians and the Jews were having a jamboree
The Buddhists and the Hindus joined on satellite TV
They picked their four greatest priests
And they began to speak
They said "Lord the plague is on the world
Lord no man is free
The temples that we built to you
Have tumbled into the sea
Lord, if you won't take care of us
Won't you please please let us be?"
And the Lord said
And the Lord said
"I burn down your cities--how blind you must be
I take from you your children and you say how blessed are we
You must all be crazy to put your faith in me
That's why i love mankind
You really need me
That's why i love mankind" God's Song -Randy Newman
Rather than metaphor, I would prefer to say the remnants of an older etiological myth.
Yeah, but that's giving our ancestors more credit than may be due. My personal guess is that disease wiped out the Neandertals when we arrived in their homelands, much like the arrival of Europeans -- and the diseases to which they had developed immunity -- nearly wiped out the native populations in the Western Hemisphere.
Arbeit macht frei...
If the cild was dead, then there was no chance for it to pass on its DNA.........
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