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Date Posted: 16:36:33 10/06/04 Wed
Author: Lijdrec
Author Host/IP: ca-01.cinergycom.net / 216.135.2.28
Subject: Y-chromosome Adams vs Mitochondrial Eves - age differences.
In reply to: Lijdrec 's message, "Final Draft" on 21:58:15 08/24/04 Tue

Now comes a fascinating new paper in press at Molecular Biology and Evolution. Scientists at the University of Arizona suspected that some of the confusion over Adam and Eve might be the result of comparing the results of separate studies on the Y chromosome and mitochondrial DNA. One study might look at one set of men from one set of ethnic backgrounds. Another study might look at a different set of women from a different set of backgrounds. Comparing the studies might be like comparing apples and oranges. It would be better, the Arizona team decided, to study Y chromosomes and mitochondrial DNA all taken from the same people. Obviously, those people had to be men. The researchers collected DNA from men belonging to three populations--25 Khosians from Southern Africa, 24 Khalks from Mongolia, and 24 highland Papuan New Guineans. Their ancestors branched off from one another tens of thousands of years ago.

The results they found were surprisingly consistent: the woman who bequeathed each set of men their mitochondrial DNA was twice as old as the man whose Y chromosome they shared. But the ages of Adam and Eve were different depending on which group of men the scientists studied. The Khosian Adam lived 74,000 years ago, and Khosian Eve lived 176,500 years ago. But the Mongolian and New Guinean ancestors were both much younger--Adam averaged 48,000 years old and Eve 93,000 years.

You wouldn't expect these different ages if a single Y chromosome had been favored by natural selection, the Arizona team argues. Instead, they are struck by the fact that Khosians represent one of the oldest lineages of living humans, while Mongolians and New Guineans descend from younger populations of immigrants who left Africa around 50,000 years ago. The older people have an older Adam and Eve, and the younger people have a younger one. The researchers argue that some process has been steadily skewing the age of Adam relative to Eve in every human population.

Now here's where things may get a little sticky for the "one-man-one-woman-is-traditional-and-natural" camp. The explanation the Arizona scientists favor for their results is polygyny--two or more women having children with a single man. To understand why, imagine an island with 1,000 women and 1,000 men, all married in monogamous pairs, just as their parents did, and their grandparents, and so on back to the days of the first settlers on the island. Let's say that if you trace back the Y chromosomes in the men, you'd find a common ancestor 2,000 years ago. Now imagine that the 1,000 women are all bearing children again, but this time only 100 men are the fathers. You'd expect that the ancestor of this smaller group of men lived much more recently than the common ancestor of all 1,000 men.

Scientists have proposed that humans have a history of polygyny before (our sperm, for example, looks like the sperm of polygynous apes and monkeys, for example). But with these new DNA results, the Arizona researchers have made a powerful case that polygyny has been common for tens of thousands of years across the Old World. It's possible that polygyny was an open institution for much of that time, or that secret trysts made it a reality that few would acknowledge. What's much less possible is that monogamy has been the status quo for 50,000 years.

People are perfectly entitled to disagree over what sort of marriage is best for children or society. But if you want to bring nature or tradition into the argument, you'd better be sure you know what nature and tradition have to say on the subject.

Posted by Carl at 5:28 PM
Read the rest...

Trackback from The Panda's Thumb, Aug 23, 2004 6:16 PM
Of course even if Pres. Bush was correct in his claim that one-man/one-woman was how it was done, it would not follow that it is preferable. And that polygyny was common in the past does not mean that it is preferable now.

It is interesting that fundamentalists who argue one-man/one-woman must do it while ignoring polygyny was fully accepted in the Old Testiment. It is amazing how changable the fundamentalists unchangable laws are.

--
Anti-spam: replace "usenet" with "harlequin2"


Posted by Mike Hopkins on August 23, 2004 09:02 PM | Permalink to Comment
Actually, if we want to take reproduction back to its biological roots, then we really should consider cloning. I mean, it was good enough a billion years ago, and I suspect it remains so to this day for the majority of individuals contributing to the world's biomass. It's just a perverse minority that uses sex for children.

Posted by oliver on August 23, 2004 10:12 PM | Permalink to Comment
Really interesting. Polygyny doesn't require one man plus multiple wives at the same time, although that explanation may be the most likely. Other possibilities: if men tended to outlive women, then serial monogamy would produce the same result. So would "monogamy" where female infidelity occurs, and multiple women tended to choose the same outside male for the extra-pair relationship.

Posted by Brian on August 24, 2004 02:31 PM | Permalink to Comment
Tell that to Mrs. Coolidge....

Excerpt: An anecdote from The Red Queen: Learning that a cockerel could have sex dozens of times a day, Mrs. Coolidge said: "Please tell that to the president." On being told, Mr. Coolidge asked, "Same hen every time?" "Oh, no, Mr....

Read the rest...

Trackback from Gene Expression, Aug 24, 2004 5:32 PM

Why is polygyny the preferred alternative to natural selection? What rules out patrilocality?

This study says the difference can be explained by patrilocality, while polygyny a factor, not the norm.

"Genetic evidence for a higher female migration rate in humans"

"A higher female than male migration rate (via patrilocality, the tendency for a wife to move into her husband's natal household) explains most of this discrepancy, because diverse Y chromosomes would enter a population at a lower rate than mtDNA or the autosomes. Polygyny may also contribute, but the reduction of variation within populations that we measure for the Y chromosome, relative to the autosomes and mitochondrial DNA, is of such magnitude that differences in the effective population sizes of the sexes alone are insufficient to produce the observation."

This study indicates polygyny is a factor, but not normative.

Reduced Y-Chromosome, but Not Mitochondrial DNA, Diversity in Human Populations from West New Guinea

"We find that genetic variation in WNG is characterized by a reduced diversity of Y-chromosome DNA but not of mtDNA. This seems to reflect cultural features of these Papuan societies, such as their patrilocal residence, their patrilineal and exogamous social clan system, and the high frequency of polygyny. In addition, warfare, which existed until recently in WNG groups and mainly affected men but not women, may have contributed to a reduction of paternal but not maternal genetic lineages. Our data further provide evidence for primarily female-mediated gene flow within the highlands of New Guinea but primarily male-mediated gene flow between highland and lowland/coastal regions, both in WNG and PNG."


Posted by joel on August 24, 2004 06:10 PM | Permalink to Comment
This question may be naive but what about DNA variation in mitochondria within an individual (or cell). Presumably a mutagenic event (at the molecular level) effects only one of the thousands of mitochondria in a single cell and an oocyte contains a (mutated) copy of the population (or a subpopulation?) of the maternal mitochondria. Does this lead to different rates for the mtDNA and Y-DNA clocks and if so how accurately are these differences known.
It might be illuminating to study Y and mt-DNA ages in other great ape populatons whose sexual behaviour is known to be polygonous (Gorilla) or promiscuous (Bonobo, Chimp?).

Posted by Greyshade on August 24, 2004 09:16 PM | Permalink to Comment
If I argued for polygamy, my fiancee would kill me. I'd postulate that polygamy is more prevalent in relatively more chauvanistic societies, and from that perspective, it is progress that we've moved towards monagamy.

On a different note, has anyone attributed to chance the fact that we have common ancestors if we go far back enough in time? How similiar is human mitochondria similiar to other hominid mitochondria? If we could prove there was a time before this speciation occurred, that would irrefutably change everyone's views.

Posted by Nightmare on August 25, 2004 04:06 PM | Permalink to Comment
I am no expert on these points, but a couple well known historical facts bear on this discussion. (1) Until the 20th century childbearing age women died at a very high rate during pregnancy and labor. The result is a male might marry several women and bear children by several women frequently. (2) Until recently the usual state of society included intermitent war. In this condition, traditions often existed for the newly widowed women to either become impregnated by or marry the surviving men. Again creating a condition that led to many men having offspring from multiple women. (3) At one point, victors typically enslaved surviving women of the vanquished and at the same time as capturing them rape was normal. Again increasing the number of women a man might impregnate.

Thus, I would be hesitant to conclude whether "monogamy" was or was not the norm. I would conclude that a number of factors existed that increased the probability of men siring children by multiple wives. Also, I suspect the likelihood is that all the conditions I've highlighted and that the article underscores tend to (1) generally increase the likelihood and (2) especially increase the likelihood if social status was greater of fathering many children by mulitple mothers for the following reasons:

1) Higher ranking individuals had more wealth and power and could more easily support multiple wives or concubines.
2) Higher ranking individuals were more likely to be awarded more slaves in case of a victory.
3) Higher ranking more "heroic" individuals were likely to be more desired by surviving widows upon return from battle even if they did not marry them and they went on to other future husbands.
4) Higher ranking individuals had better access to better food and health care (rudimentary as it may have been) allowing them to continue procreating longer and increasing the chances of outliving multiple childbearing age spouses.
5) Higher ranking individuals offered better security to childbearage women increasing the possibility of continuing to have new children by
multiple spouses for a much longer span of years. On the other hand, less affluent individuals might tend to only have one spouse who upon reaching menopause effectively stopped addition to the line.

Finally, I believe the Bible offers a very good "ancient" narrative record of almost all these behavioral events occuring and their affect on procreation by men and women if carefully traced.

Posted by Blake Ratcliff on September 6, 2004 07:12 AM | Permalink to Comment
This is very intresting. But iam hearing that the mt DNA, now a yes or no question, is it true that the chance stand greater for this DNA stran to be trased back to one female in africa that maybe connected to the Anunnaqi name ninti.

Posted by JONAH MOSES on September 17, 2004 06:17 PM | Permalink to Comment
5 Jahre Erdgas Arena - JubilÄumsprty http://tickets.gelago.de/cat3396/Konzerte/Rock-pop/5-Jahre-Erdgas-Arena-JubilÄumsprty/

Posted by 5 Jahre Erdgas Arena - JubilÄumsprty on September 18, 2004 04:38 AM | Permalink to Comment
It seems more likely that a woman would evolve into a man than a monkey, and the idea that a woman would evolve into a man is ridiculous enough. GOD has designed the universe, and did not create anything by accident. Each hair on your head is numbered by GOD, and no doubt each thought is read by HIM. If each thought is read by HIM, then each man is accountable to GOD, and no amount of falty reasoning will release any from this fact. Don't believe the lie, GOD was in CHRIST reconciling the hell bound world to himself, but many have gone after vain imaginations, to thier own eternal peril.

Posted by Roussan on September 22, 2004 06:22 PM | Permalink to Comment

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[> [> [> [> [> [> Genetics, Evolution, Fertility and Gays -- Lijdrec, 22:54:58 10/25/04 Mon (ca-01.cinergycom.net/216.135.2.28)

Now just last night/early this morning in London comes news of a study by some Italian researchers into homosexuals and their families and how it might relate to fertility, evolution and the X chromosome --- and everything they hypothesize about seems to fit my ideas!! Here is a Google News archive of articles and the following is from the London Times Online....

http://www.timesonline.co.uk/article/0,,2-1306894,00.html

--------------------------------------------------------------------------------

Britain

October 13, 2004

So it is down to mother: gay gene survives because it boosts fertility

By Mark Henderson, Science Correspondent

London Times Online

THE biological enigma of how homosexuality evolved despite its obvious drawbacks for reproduction may finally have been resolved.

The genes that make men gay also help their female relatives to have bigger families, according to new research.


Scientists have discovered that gay men’s mothers, sisters and maternal aunts tend to have significantly more children than the norm — and that many of their nephews and male cousins are also gay.

The findings suggest that the same genes that trigger homosexuality in men also promote fertility in women, and that this could explain how they survive in the population when gay men themselves are unlikely to breed. The genes are instead passed on through the female line and the enhanced fertility they confer on these women ensures that they are inherited by plenty of children.

Some of these sons will grow up to be homosexual themselves. The study also revealed that gay men are more likely than heterosexuals to have a gay male relative, though only on their mother’s side of the family.

The results, from the University of Padua, in Italy, offer strong support for the theory that homosexuality is at least partly determined by a person’s genetic make-up, and is not just about personal choice or upbringing and environment. It also suggests an elegant solution to the biggest problem with this hypothesis — the “Darwinian paradox” that any genes that favour homosexuality ought to have died out through natural selection, as those that inherited them had fewer and fewer offspring.

Andrea Camperio-Ciani, who led the research, said: “Our data resolve this paradox by showing that there might be hitherto unexpected reproductive advantages associated with male homosexuality.”

The work also points to a likely location for the genes that have this effect: they almost certainly lie on the X chromosome, the package of DNA that men always inherit from their mothers.

In the study, published today in the journal Proceedings of the Royal Society, Dr Camperio-Ciani’s team interviewed 98 homosexual and 100 heterosexual men in detail about their extended families. In total, more than 4,600 individuals were thus indirectly involved. They found that both the mothers and maternal aunts of the homosexuals were significantly more fertile than those of the straight men: the mothers had an average of 2.69 children compared with 2.32, and the aunts 1.98 children compared with 1.51.

Fertility rates among paternal relatives and among male relatives on the mother’s side were similar for both groups.

All this points to genes that influence both male homosexuality and female fertility being passed down along the maternal line. “The results hypothesise that genetic factors, transmitted in the maternal line, increase both the probability of being homosexual in males and fecundity in females,” Dr Camperio-Ciani said.

The study did not investigate lesbianism. The notion that homosexuality has at least some basis in biology is not now seriously disputed by scientists, though there is little consensus on what the causes might be. Some scientists think that genetics are critical, while others believe that conditions in the womb are all-important.

The question of what causes homosexuality has long divided both the gay community and social conservatives who regard same-sex partnerships as wrong. Many gay activists think that identifying biological factors that contribute to homosexuality will prove that their sexual orientation is perfectly natural and encourage tolerance. Others fear that it will lead to greater hostility, with the risk that being gay will again be seen as a disorder that might one day be “cured”.



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Wonder what this would mean to the world view of many religions?
...


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