Mongolian Spots
Posted on 01/08/2002 3:29:31 PM PST by blam
January 8, 2002
Genes Help Identify Oldest Human Population
By NICHOLAS WADE
Peering deep into the archive of population history that is stored in the human genome, a Stanford University biologist believes he has picked up a genetic signature of the ancestral human population.
The signature, a pattern of genetic changes on the male or Y chromosome, is apparent in some present- day Ethiopians and in the Khoisan, click language speakers who now live in South Africa.
The researcher, Dr. Peter A. Underhill of Stanford University, believes these people may include descendants of the ancestral human population that occupied the eastern region of Africa in the Paleolithic era.
"If you could go back in a time machine and sample Africa 30,000 years ago, there must have been a population continuum from Ethiopia to southern Africa, a sparse population because they were all foragers, but one that must have had a common ancestor," Dr. Underhill said.
The finding, which he and colleagues report in the December issue of The American Journal of Human Genetics, complements an earlier study based on mitochondrial DNA, which is inherited only through the female line.
This study, by Dr. Douglas Wallace of Emory University, indicated that the most ancient human populations are the Vasikela Kung of the northwestern Kalahari desert in southern Africa and the Biaka pygmies of Central Africa.
Most parts of the human genome are shuffled between generations, making it hard to sort out the pattern of inheritance. Two exceptions are the Y chromosome, which descends through the male line, and the DNA of mitochondria, the energy-producing organs of the cell, which are transmitted only through the mother.
These two segments of DNA have been inherited unchanged from the ancestral human population, except for occasional rare changes or mutations in the DNA caused by radiation, copying errors or other damage.
This makes it possible to draw up a human family tree based on the series of mutations that accumulated over time as people emerged from the ancestral human cradle in Africa and spread out across the globe. Such trees were drawn up by Dr. Wallace and others, based on mitochondrial DNA, and more recently by Dr. Underhill and his colleagues, based on mutations they found in the Y chromosome.
The deepest branches in these gene trees — the ones that join nearest to the point of origin — presumably represent populations that are closest to the ancestral human population.
Dr. Underhill finds that the earliest mutations in his Y chromosome tree are found at high frequency among the Khoisan and also among the Oromo and Amhara peoples of Ethiopia.
Many early lineages in the ancestral population are likely to have been lost, however, and it is a matter of chance which survive, Dr. Underhill said.
So it is not surprising that the earliest branches on his Y chromosome tree lead to a different set of populations than those in Dr. Wallace's mitochondrial DNA tree. Both trees point to the Khoisan, however, since Kung speakers are members of the Khoisan language family.
Archaeologists tracing the ancient distribution of the San people, part of what is now referred to as the Khoisan, believe that in Paleolithic times they occupied the eastern half of Africa from Ethiopia to South Africa. Dr. Underhill said this distribution matched that inferred from his Y chromosome studies.
These earliest Y chromosome lineages, he said, "are found only in Africa and seem to be associated with these hunter-gatherer-forager lifestyles." He believes the men carrying these lineages began to spread out in Africa from 130,000 to 70,000 years ago, based on the estimated rate at which genetic changes accumulate in the Y chromosome.
About 50,000 years ago, a new lineage arose and a population from this lineage migrated out of Africa to southern Asia and Australia. Then another lineage derived from the Asian population reached Europe 30,000 to 20,000 years ago.
The genetic changes studied by Dr. Underhill occur in regions of the Y chromosome that do not code for genes or their control regions, and have no effect in the people who carry them.
Probably worded this way for PC fears of referring to the Bushmen as either primitive or pure.
I'm having trouble framing this, too. We are all descended
from the same ancient population, else whence? Is this
a distinction without a difference, or is it a way of saying
they have found a profoundly primitive human genotype,
but lack the testosterone to say so?
Most of the DNA studies dealing with ancients is usually done using mtDNA (the female line), this study apparently was done using the Y chromosome (male line) and in doing so an ancient population 'popped' up that otherwise would not have using the mtDNA. Am I reading this wrong?
Thanks for the critical appraisal. Do you have anything informative to add to the discussion?
If this is science, then why all the presuppositions about the origins if we are trying to determine the origins?
For all the trash that has been produced over the past 100 years, isn't it a bit amazing how little of it ever remains more than about 20 years. Take this back a 1000 years and remarkably scant remains exist. Now attempting to extrapolate these features out to the point of having to produce exponential timelines simply to account for a forced presupposition that all humans were foragers, let alone claiming undeniable proof of their existence beyond about 5000-6000 years seems to borrow much more substance from present arrogance than from sincere truth searching.
I would like to be able to respect those who dedicate so much time to archeology and other methods of documenting ancient history, but I find way too much reliance on a presupposed timeline of exponential functions rather than proofs that no other answer is possible.
Considering the incredible lack of conscientiousness on the behalf of such researchers, I wonder what portion of that community even has members who are even capable of novel research. It's not the same scientific community I gre up with which was dedicated to truth, honesty, and honor for the sake of answering challenging questions. It seems much more like a contest to tickle each others ears and revel in intellectual arrogance. Just my third party viewpoint.
I don't use genes. The blue hair, big cars with AARP bumper stickers, wrinkled skin, and driving 30 miles an hour on the interstate are how I identify oldest population.
For example, Indian Brahmins result from Euro-Persian males impregnating South Asian females-their marriage and family customs have highly conserved the Y chromosome DNA but not so the mt-DNA.
Y-DNA and mt-DNA would only give the same information if matings between invader males and native females were equally likely as matings between invader females and native males-which cannot possibly be true.
Interesting stuff.
Some things I learned about the Bushmen:
*They are shy and retreating. They always run and hide, never fighting. They hide in the bushes and rocks when anyone approaches.
*They are very small (At least the 'real' Bushmen)
*They have the most primitive language on earth.
*They dance around fires all night in gay merriment
*They have pointed ears
*They are not black
*They have a Mongoloid spot at birth (as do most Asians at birth)
*The females have an 'apron' over the genetial area
*They have oversized buttocks (some tales say they function as a source of moisture storage, like camel humps)
*All other people in Africa call them the ancient ones
*Their presence is recorded in the Egyptian glyphics, including their physical uniqueness.
*There are no longer any 'pure' Bushmen, they are mixed with the Bantus (blacks)
I also came across the Fomorians as a source of the term 'black Irish' in Ireland. (The Spanish Armada was not the source of this term). But, this another whole story, for later.
So, unless both the Y-DNA and the mt-DNA are considered in any sample population, then you're not getting a true picture of that population? That would make The Seven Sisters/Daughters Of Eve stories BS, huh?
Mongolian Spots
I've been busy on the Governor Davis threads , he may be related to some of the ancient ones!
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