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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: CobaltBlue
"Sorry if I am coming across too tough. I am feeling rather grumpy today. I'll try to be more polite. ;^)"

I meant 'tough' in a nice way. You're making me back-up my statements today.

81 posted on 02/02/2004 3:44:17 PM PST by blam
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To: CobaltBlue
They've got ever larger pools of DNA from living people, and they use models of genetic drift to estimate the time it must have taken for the changes

So, much of this is based on the assumption the model is correct? Is it possible to create a model that points to 'adam' and 'eve' living 200,000, 500,000, or more years ago? Or possibly fewer then 60,000 years ago?

Just curious

82 posted on 02/02/2004 3:59:46 PM PST by yhwhsman ("Never give in--never, never, never, never, in nothing great or small..." -Sir Winston Churchill)
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To: KingNo155
The key word is venerated. Many do not understand the difference between venerated, when soemthing is used for inspiration in devotions, and adoration.

Regards.

83 posted on 02/02/2004 4:05:57 PM PST by TheGeezer
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To: rmlew; Clemenza; nutmeg; firebrand
btt
84 posted on 02/02/2004 4:49:17 PM PST by Cacique
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To: Brilliant
It does fit with the Biblical account. The "genetic Adam", the father of all male lines of descent still around, was Noah, since the only other males on the Ark were his sons. The "genetic Eve" was Eve herself, since Noah's sons brought their wives, and there were three of them.
85 posted on 02/02/2004 5:23:12 PM PST by A.J.Armitage (http://calvinist-libertarians.blogspot.com/)
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To: chance33_98
Bump for later perusal
86 posted on 02/02/2004 5:25:43 PM PST by carpio
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To: Doctor Stochastic
"Were tests to be done with other genetic markers (if any be available), other results may obtain."

I think that is not totally true, all genetic markers should follow the Y and mitochrondrial reults to some extent. given the Y and mitochondral results, should we not be able to recreate the entire makeup of Eve, and Adam?

87 posted on 02/02/2004 6:57:50 PM PST by FastCoyote
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To: FastCoyote
Not necessarily. This "Eve" lived about 90,000 years before this "Adam." Check out the links in post 37.

88 posted on 02/02/2004 7:02:45 PM PST by Doctor Stochastic (Vegetabilisch = chaotisch is der Charakter der Modernen. - Friedrich Schlegel)
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Comment #89 Removed by Moderator

To: yhwhsman
My understanding is that the only assumption is the rate of genetic drift.

It is a fact beyond peradventure that your mitochondrial DNA is inherited from your mother and only your mother.

Similarly, if you are male, it is a fact beyond peradventure that your Y chromosome DNA is inherited from your father and only your father.

It is also a fact that all humans today possess DNA which is a variation on a theme, and that theme is many thousands of years old.

The only question is how many thousands of years from the origin of the DNA to you.

200,000? Maybe. Less than 60,000? Maybe.
90 posted on 02/02/2004 8:13:30 PM PST by CobaltBlue
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To: PinkPunk
Is this to imply that Eve had an immaculate conception, with no Adam around at the time?

Nothing in the article implies that there were no men (or other women) alive at the time. See the links in #37.

91 posted on 02/02/2004 8:37:33 PM PST by Doctor Stochastic (Vegetabilisch = chaotisch is der Charakter der Modernen. - Friedrich Schlegel)
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To: Doctor Stochastic
True. These aren't the ur-parents. These are just nexi through which all lines of descent pass.

Enough of the discussion. When does the halftime show start?

;)

92 posted on 02/02/2004 9:03:29 PM PST by <1/1,000,000th%
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To: CobaltBlue
The DNA studies don't use bones. Certainly not for Y-chromosome DNA, it doesn't last long enough.

I was probably being unclear in my post. The poster I was responding to seemed to believe that just because the bones of the so-called "Adam" were found in Africa doesn't mean he was from there. I was trying to point out that the idea of a group of hunter-gatherers travelling hundreds if not thousands of miles while carrying the body of a deceased member of the group was ludicrous.

93 posted on 02/03/2004 10:17:34 AM PST by Modernman ("The details of my life are quite inconsequential...." - Dr. Evil)
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To: chance33_98
Mind-boggling to think about.
94 posted on 02/03/2004 10:26:15 AM PST by Ciexyz
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To: cajun-jack
"If i am going to err, it will most certainly be on the side of caution."

Then you are not walking in faith, you are walking in fear. Go see what the Boook says about this condition (I'll give you a hint: it's not recommended).
95 posted on 02/03/2004 10:31:03 AM PST by webstersII
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To: Modernman
No prob. Just wanted to make sure that you knew that there were no bones, no "Adam", it's a statistical hypothesis, but a very interesting one.

On a somewhat different but related topic, I was surprised to learn recently that DNA testing confirms that dogs are not actually related to coyotes or jackals. Wolves only.
96 posted on 02/03/2004 10:36:53 AM PST by CobaltBlue
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To: Doctor Stochastic
Not to mention the Gameboy.
97 posted on 02/03/2004 10:37:08 AM PST by T Minus Four
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To: T Minus Four
Probably powered by torsion of wound up animal skins.
98 posted on 02/03/2004 10:45:49 AM PST by Doctor Stochastic (Vegetabilisch = chaotisch is der Charakter der Modernen. - Friedrich Schlegel)
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To: webstersII
I know what i'm doing..just trying to make a softer landing for the "anti" crowd...but thanks for your concern.
99 posted on 02/03/2004 4:49:36 PM PST by cajun-jack
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To: cajun-jack
I don't really agree with that tactic, but that's your business.
100 posted on 02/04/2004 6:22:56 AM PST by webstersII
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