Posted on 02/03/2003 1:02:30 PM PST by vannrox
In July of 1997 the first ever sequencing of Neanderthal DNA was announced in the Jouranl Cell (Krings, et. al., 1997), a breakthrough in the study of modern human evolution. The DNA was extracted for the type specimen and the mitochondrial DNA sequence was determined. This sequence was compared to living human mtDNA sequences and found to be outside the range of variation in modern humans. Age estimation of the Neanderthal and human divergence is four times older than the age of the common mtDNA ancestor of all living humans. The authors suggest that the Neanderthals went extinct without contribution to the present mtDNA of modern humans.
The Neanderthals inhabited Europe from about 300,000 to 30,000 years ago. Previous hypothesis that Neanderthals were replaced relied on mtDNA study of existing populations. Directly analyzing the remains of the Neanderthal type specimen has affirmed this view.
The researchers removed a sample from the humerous specimen. They analyzed the extend of amino acid racemization to determine suitability for analysis. It was determined that the amino acid levels were at 20% to 73% of those in modern bone, evidencing DNA survival. This and other tests indicated the remains might contain amplifiable DNA. Amplification products were cloned. Twenty seven clones of obvious non-human origin were produced. The entire sequence of hypervariable region 1 was determined, 387 positions. This was accomplished with overlapping segments.
In comparison to modern DNA 27 differences are seen. The Neanderthal sequence was compared with 2051 human and 59 chimpanzee sequences over 360 base pairs. Twenty five of the 27 variable base pairs coincide with positions that vary in at least one of the human sequences. The sequence was compared with 994 human mtDNA lineages. While these lineages differ among themselves by eight substitutions on average, the range of difference with the Neanderthal sequence is 22-36. The Neanderthal sequence has 28.2 ±1.9 substitutions from the European lineage, 27.1 ±12.2 substitutions from the African lineage, 27.7 ±2.2 substitutions from the Asian lineage, 27.4 ±1.8 substitutions from the American lineage, and 28.3 ±2.7 substitutions from the Australian/Oceanic lineages. This indicates no closer a relationship with Europeans.
The comparison to chimpanzees with modern humans is 55.0 ±3.0, compared to the average between humans and Neanderthals of 25.6 ±2.2. these results indicate a divergence od the human and Neanderthal lineages long before the most recent common mtDNA ancestor of humans. Based on the estimated divergence date of 4-5 million years ago for humans and chimpanzees, the authors estimate the human and Neanderthal divergence at 550,000-690,000 years ago. The age of the common human ancestor, using the same procedure, is about 120,000-150,000 years ago.
These results do not rule out the possibility that Neanderthals contributed other genes to modern humans. However, the results support the hypothesis that modern humans arose in Africa before migrating to Europe and replacing the Neanderthal population with little or no interbreeding.
In March of 2000 the results of a second fossil Neanderthal DNA sequencing was announced in the Journal Nature (Ovchinnikov, et. al., 2000). The fossil specimen is an infant from the Caucasus region dating to less than 30,000 years ago. A rib was used in the DNA isolation and 345 base pair sequence was produced. The specimen had 22 base pair differences, compared to 27 for the type specimen, over the 345 base pair sequence. The two Neanderthals share 19 substitutions. Although the two Neanderthals were separated by 2,500 km they are closely related in mtDNA lineages.
This second study estimates the most recent common ancestor of the Neanderthals at 151,000-352,000 years, while the human and Neanderthal divergence is placed at 365,00-853,000 years. The same model produces an age for the modern human divergence of 106,000-246,000 years.
Sources:
Krings, M., A. Stone, R. W. Schmitz, H. Krainitzki, M. Stoneking, and S. Pääbo. 1997. Neanderthal DNA Sequences and the Origin of Modern Humans. Cell 90:19-30.Ovchinnikov, Igor V., A. Götherström, G. P. Romanoval, V. M. Kharitonov, K. Lidén and W. Goodwin. 2000. Molecular analysis of Neanderthal DNA from the northern Caucasus. Nature 404:490-493.
That's got to be a typo. +/-2.2 would be much more in-family with the other lineages. Unless African DNA is inherently more diverse than non-African, which I have to doubt.
She's a drag!
Actually, it is; I believe there's more genetic diversity in Africa than the whole rest of the world combined. You've got a lot of odd groups there; what's left of the San Bushmen, the Pygmies, etc.
More variation between a South African and a Nigerian than between a Norwegian and a Greek....
Not true. My ex wife's family is still alive.
I believe you're right. Here's some data from another study:
"We observed this in our analysis—the average pairwise differences between the Neanderthals and 300 randomly selected Africans, Mongoloids and Caucasoids were calculated to be 23.09 +/- 2.86, 23.27 +/- 4.06 and 25.45 +/- 3.27, respectively."
Molecular analysis of Neanderthal DNA from the northern Caucasus
04/22/2001
Sunday Times - London
News International
1GW
12
(Copyright Times Newspapers Ltd, 2001)
ONLY a week after Anne Robinson was let off for pouring scorn on the Welsh, another group of oppressed Celts have come in for a pasting. Scientists at Oxford University have let rip at Scotland's most oppressed minority - the ginger. Experts at the Institute of Molecular Medicine have confirmed the views of playground bullies and declared that carrot-tops are genetic throwbacks, descended from Neanderthal man. The Neanderthals were aggressive thugs who hung about Europe 50,000 years ago. It had been assumed their genes had all died out as clever homo sapiens took over their turf. But now scientists believe that Neanderthal genes live on in those who have red hair.
About 40% of Scots have ginger genes and 10% have red hair. But though Scotland's redheads haven't necessarily inherited the sloping brows and dragging knuckles of their great great great-grandpas, the Oxford scientists maintain that the flame-haired have inherited a fiery temper and tendency to be unruly. But only a few months ago another set of scientists were explaining that ferrous follicles were a genetic gift, ensuring redheads were prized above all others. At the time a scientist declared "red hair has been a sign of beauty for generations". This must come as a consolation to redheads who have hidden their shining glory under such euphemisms as "russet", "auburn" and "flame". And what of Archie MacPherson, Jackie Bird, and Charles Kennedy, apparently peace-loving, but bedecked with Irn-Bru colouring? How will their public profile be affected by news that the heart of savage man beats within them?
Exactly where do you think they were on the chart?
Serious query. Do you think it might once again be re written in the next 30 years? What are the possibilities for new discoveries?
My own thoughts are that we have only scraps of possible evidence...who knows what new technologies might reveal.
I can't vouch for the exact number, but African DNA IS much more diverse than that of the rest of the world. Time and additional research may alter the picture, but the current thinking is that all Europe, Asia, Australia, and the New World are descended from one small group of Africans that crossed over into the Middle East and expanded explosively into the vast empty Eurasian habitat.
Another potential explanation for the diversity of African DNA is that, for much of human history, Africa simply had a much larger population and therefore more opportunity to accumulate mutations. This would suggest a center of origin at East Africa or the Middle East, where the lineages link to the rest of the planet.
Whatever the explanation, African DNA is much more diverse than the rest of the world.
The Bible gives a brief glimpse into the past where man existed before Adam. This tends to validate it.
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