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Age of Our Ancestors-How Our Genetic Adam Is Much Younger than Genetic Eve
abcnews.go.com ^

Posted on 02/02/2004 12:31:53 AM PST by chance33_98

Age of Our Ancestors

How Our Genetic Adam Is Much Younger than Genetic Eve

Commentary By John Allen Paulos

Feb. 1 — A new book, The Journey of Man, demonstrates how recent advances in genetics, particularly those involving the Y-chromosome, allow us to follow the arc of human migration out of Africa, our ancestral home.

Although Neanderthals and other hominids related to Homo sapiens date back hundreds of thousands of years, the book's author, geneticist Spencer Wells, shows that our origins are much more recent. Presenting the work of Luigi Luca Cavalli-Sforza, Richard Lewontin, and other eminent researchers, Wells argues convincingly that all men on earth (the Y-chromosome is passed only from father to son) can trace their roots to a particular male who lived in Africa, almost 60,000 years ago.

Likewise, all humans on earth can trace their lineage through our maternally inherited mitochondrial DNA back to a particular woman, who lived in Africa roughly 150,000 years ago. This "Adam" is my great-grandfather roughly 2500 times removed and this "Eve" my great grandmother roughly 6500 times removed. (Yours too, so we're all distant cousins.)

In coming to these conclusions, Wells relies upon a variety of mathematical techniques, ranging from statistical tests to measure the similarities between and among the genomes of present-day populations to carbon dating and other methods commonly employed at archeological sites.

The probability of branching processes lends additional support as does empirical research on the world's various ethnic groups. Most revealing is the use of the rate at which random mutations naturally occur to infer the paths of our ancestors around the globe.

Family Recipes as a Metaphor

Wells employs a culinary metaphor to clarify the notion of a genetic Eve, whose existence was long disputed by those who believed that mankind developed independently in several locations around the world. Altering Wells' metaphor a little, let's imagine a small village that has been inhabited for millennia. Imagine further that we go way back in time and note that the few families in the village use different recipes for their primary meal, and that the recipes are handed down from mother to daughter only.

Very complex, the recipes can be modified in hundreds of ways — a different ingredient here, longer cooking time there, etc. — and every once in a while a daughter makes a tiny change in her mother's recipe, which she then passes down to her daughter(s). Sometimes because of accident, disease, or simply a line's not having any daughters, a family's recipe and its variants die out. In fact, let's assume that all but one of the original recipes and their variants disappear. Thus in the village we can now find only one of the dozen original recipes, dating back X thousand years, and its many variants.

If for the village we substitute Africa, and for recipes we substitute the human genome, the surviving original recipe is analogous to the genetic makeup of African Eve since all the surviving recipes derive from it just as we all can trace all our mitochondrial DNA back to a particular woman who lived 150,000 years ago.

And just as our mitochondrial DNA is inherited only through our mothers, the male Y-chromosome is passed only from fathers to sons. So let's invent another just-so story about, say, elaborate hunting rituals that are passed down from father to son with very rare changes. We again go back to a time when there were very few families and hence few different hunting rituals.

Once again, each of these elaborate hunting rituals changes very slowly. Furthermore, because of famine, disease, or not having any sons, a family's hunting ritual and its variants die out. Let's assume that all but one of the original rituals and their variants disappear. Thus in the village we can find only one of the few original rituals, dating back Y thousand years, and its many variants, and thus conclude that all existing rituals derive from the original one, the analogue of a genetic Adam.

The Paths We Took

Note that X and Y need not be equal since recipes and hunting rituals will no doubt change and die out at different rates, so our genetic Eve did not meet our genetic Adam (and both, of course, had parents, grandparents, and other progenitors).

There is, however, much more in Journey than this absence of a prehistoric romance. As mentioned, the bulk of the book examines how geneticists study small changes in the DNA of our Y-chromosomes and use the rate at which they naturally occur as a sort of molecular clock to determine when and where various groups and clans of our prehistoric ancestors split off and spread over the earth (along the coast of India to Australia, later into Eurasia, and then down to the Americas across the Bering Sea).

If we know where we originated, and if a distinct recipe or ritual and its descendants, to revert to our metaphor, appears only in a neighboring village, then this (along with much other evidence) indicates that these people left the original village at a certain time. And if their descendants' recipes and rituals appear only in an even more distant village, then these others left still later.

The common childhood game in which we change, a letter at a time, one sequence of letters into another — say GENE to GONE to GORE to MORE to MARE to MARS — also sheds some light on what geneticists do when analyzing the branching changes in the very long sequence of "letters" that constitute our DNA. If each of the changing sequences of letters also gave rise to other changing sequences of letters and if some of these sequences split off and moved to different physical locations, we would be led to the sort of considerations and methods that are described in The Journey of Man.

We've come a long way, and the fascinating, sometimes counterintuitive details of the trip are finally becoming a little clearer.


TOPICS: Miscellaneous
KEYWORDS: archaeology; dna; genetics; ggg; godsgravesglyphs; history
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To: Cronos
Maybe he traveled in "Dream Time"? Just ask "the people" (Australian Aborigines).
61 posted on 02/02/2004 10:57:22 AM PST by Woodman ("One of the most striking differences between a cat and a lie is that a cat has only nine lives.")
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To: Old Professer
Simple.

Women were hatched until approximately 60,000 years ago.

At that time, males were created, and contributed the 'brain'.

Unfortunately, the species only passes them only to the male offspring.
62 posted on 02/02/2004 10:59:20 AM PST by Stallone (Socialism is a women's disease)
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To: Stallone
What else explains Socialism?
63 posted on 02/02/2004 11:00:18 AM PST by Stallone (Socialism is a women's disease)
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To: msdrby
ping
64 posted on 02/02/2004 11:00:58 AM PST by Professional Engineer (Spirit/Opportunity~0.002acres of sovereign US territory~All Your Mars Are Belong To US)
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To: CobaltBlue
all that tells us is that that part of DNA was less in need of change over time than the other parts of DNA.

I am not being stubborn. I am just stating that if it worked there was no reason to fix it.

I am also stating the ABCnews article does employ some PC spin.
65 posted on 02/02/2004 11:02:02 AM PST by longtermmemmory (Vote!)
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To: longtermmemmory
I am baffled by your assertion that politics has anything to do with this. It has nothing to do with feminism, nor PC.

I do geneaology as a hobby. Some people don't have children, and so their branch on the genetic tree dies off. Maybe they died young. That doesn't mean that the ones who have children are better people.

We're all descended from a long, long line of people who survived long enough to procreate. If you trace the genes back far enough, they're all related to one woman who lived about 120,000 years ago, probably in Africa, and one man who lived about 60,000 years ago, probably also in Africa.

The disparity in time suggests that human beings almost died out for some reason we can only imagine.
66 posted on 02/02/2004 11:06:26 AM PST by CobaltBlue
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To: longtermmemmory
Your buddy Stallone just posted a theory that the article shows that men are better than women. That should make you happy, and you can stop pouting.
67 posted on 02/02/2004 11:09:13 AM PST by CobaltBlue
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To: CobaltBlue
piddle.

Such who is more entitled to the remote is useless. The real issue here to me is the fact ABC is taking some other article and misusing it.

This is no differnt than saying portions of our brain are reptilian.

I have seen journal articles which purported that the Y chromosome was subject to very little change. This lead to arguments and spin in some "other" direction. All piddle.

My background includes hard science biology. The media usually gets it wrong based on their personal agenda. One should not just be sceptical about such articles one should disbelieve them FIRST and then have them proven correct. They are just trying to sex it up.
68 posted on 02/02/2004 11:17:19 AM PST by longtermmemmory (Vote!)
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To: longtermmemmory
Astonishing. Words fail me. Well, not for long, words never fail me for long. -g-

So, if the shoe were on the other foot, and "Adam" were 120,000 years old and "Eve" were 60,000, would that make you happier?

Because what bothers you are the facts. The article is relating the facts as they are presently known to exist.
69 posted on 02/02/2004 11:22:27 AM PST by CobaltBlue
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To: Ichneumon
That's always the hard part; agreeing on what someone said when there are two or more ways of looking at it.
70 posted on 02/02/2004 11:36:22 AM PST by Old Professer
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To: longtermmemmory
Some links for you - you can probably get these books from your library.

http://www.amazon.com/exec/obidos/tg/detail/-/0393020185/ref=pd_sim_books_1/002-0045269-8427250?v=glance&s=books
http://www.amazon.com/exec/obidos/tg/detail/-/0201407558/ref=pd_sim_books_5/002-0045269-8427250?v=glance&s=books
http://www.amazon.com/exec/obidos/tg/detail/-/0618091572/ref=pd_sim_books_2/002-0045269-8427250?v=glance&s=books

Scientific American special on the topic:
http://www.sciamdigital.com/browse.cfm?sequencenameCHAR=item2&methodnameCHAR=resource_getitembrowse&interfacenameCHAR=browse.cfm&ISSUEID_CHAR=4162B5FD-F647-054F-1EE56488B04DB853&ARTICLEID_CHAR=41743B46-FEB5-AA86-1A2D5EF0BA284305

Recent articles in Nature:
http://www.nature.com/cgi-taf/DynaPage.taf?file=/ejhg/journal/v11/n3/abs/5200949a.html
http://www.nature.com/cgi-taf/DynaPage.taf?file=/ejhg/journal/v8/n9/abs/5200514a.html
71 posted on 02/02/2004 11:38:53 AM PST by CobaltBlue
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To: CobaltBlue
If you trace the genes back far enough, they're all related to one woman who lived about 120,000 years ago, probably in Africa, and one man who lived about 60,000 years ago, probably also in Africa. The disparity in time suggests that human beings almost died out for some reason we can only imagine.

It may not indicate a bottleneck. It may just mean that male lines are more subject to being snuffed out, as in warfare. When one tribe conquers another, the defeated men may be killed (or perhaps castrated). The women may be kept alive, as they are less of a threat and otherwise good to have around. Therefore, an unbroken female line can be very long indeed, compared to most -- if not all -- male lines.

72 posted on 02/02/2004 11:58:07 AM PST by PatrickHenry
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To: CobaltBlue
"Mankind may have evolved independently in several locations, but the DNA doesn't lie - if there was independent evolution, there was also convergence. So you've got to come with a theory that fits the evidence."

I was watching a documentary about the Super Volcano Toba and they explained that as few as 2,000 people worldwide survived the explosion 75,000 years ago.
Now, it wasn't a week later while watching another documentary that I saw a female archaeologist excavating a human site in Indonesia that was just above the volcano ash layer...to soon for another group to walk from Africa.

I understand that these people could have (somehow) gone extinct...But, I don't think so. Something is going on with the DNA that we don't understand....and then, there's Mungo Man in Australia.

73 posted on 02/02/2004 12:07:04 PM PST by blam
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To: blam
The most recent research I am aware of on Mungo Man shows that he's only about 40,000 years old, which certainly gave him time to have migrated from Africa.
http://www.iol.co.za/index.php?click_id=143&art_id=qw1045634408844B223&set_id=1
74 posted on 02/02/2004 12:16:27 PM PST by CobaltBlue
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To: CobaltBlue
Okay. (Boy, you're tough today, lol)

I think there are some rock painting in Australia that have been dated to 60k+ years ago. I did a search and could find anything on the net. (It's nap time for me)

75 posted on 02/02/2004 12:29:10 PM PST by blam
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To: blam
I don't doubt for a minute that human beings or something very much like them roamed the earth longer ago than 60,000 years. They were certainly in Europe before the last glacial maximum, but appear to have all been pushed back or killed off. Maybe pockets hung on for a long time, and then died off, dead ends on the gene tree.

Sorry if I am coming across too tough. I am feeling rather grumpy today. I'll try to be more polite. ;^)
76 posted on 02/02/2004 12:49:41 PM PST by CobaltBlue
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To: longtermmemmory
In the end this will be re-re-re-re-re-re-revised.

I agree with this part. Plus the article was poorly written. Common sense tells me the 60,000 year-old man had a father and inherited his DNA.

77 posted on 02/02/2004 1:21:22 PM PST by <1/1,000,000th%
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To: <1/1,000,000th%
True. These aren't the ur-parents. These are just nexi throuth which all lines of descent pass.
78 posted on 02/02/2004 1:38:26 PM PST by Doctor Stochastic (Vegetabilisch = chaotisch is der Charakter der Modernen. - Friedrich Schlegel)
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To: Doctor Stochastic
"Throuth" should be "through."
79 posted on 02/02/2004 2:49:11 PM PST by Doctor Stochastic (Vegetabilisch = chaotisch is der Charakter der Modernen. - Friedrich Schlegel)
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To: TheGeezer
I know Catholics don't worship Bones (I am Catholic) but there are many chapels that have the bones of Saints and their remains(bones,ect..) are treated as venerated objects.
80 posted on 02/02/2004 3:12:11 PM PST by KingNo155
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