Michael:

As I mentioned, I’ve been reading Spencer Wells’ book, “The Journey of Man: A Genetic Odyssey.” (You can buy it here.) In it he traces the probable routes and timetables by which anatomically modern humans ("AMHs") settled the world outside of Africa.

His main ‘tools’ in this analysis are family trees generated by mutations in mitochondrial DNA ("mtDNA")—which passes solely from mother to daughter—and by mutations in the Y-chromosome—which passes solely from father to son. Both of these show, by the way, that humanity’s most recent common ancestors—‘Adam’ and ‘Eve’, so speak—lived in Africa prior to the dispersal of humanity across the rest of the world.

Unlike the Biblical Adam and Eve, however, these two universal ancestors were by no means the first AMHs. Both of these figures had AMH ancestors of their own stretching back thousands of years; and each had many contemporary AMHs who were also busy having children. It is simply that all the other father-to-son-to-son and mother-to-daughter-to-daughter ‘lineages’ that were around at the same time as ‘Adam’ and ‘Eve’ have died out over the subsequent years.

Although for many purposes the two types of genetic data (that is, male-to-male and female-to-female) complement each other, there are instances where they show very interesting divergences. One of the most striking divergences is how much more geographically precise the information revealed by Y-chromosome mutations is. In the words of Mr. Wells:

When the Y was first studied as a marker of population affinity, one of the results that kept popping up again and again is that it connected people to a particular location. With a few DNA polymorphisms, it was possible to achieve incredible geographic resolution—there were even Y –chromosome polymorphisms that were limited to particular villages. If you imagine population genetics as a game of twenty questions, most genetic systems, including blood groups and mitochondrial DNA, needed all twenty to identify even the coarsest pattern, such as which continent the individual came from. In contrast, the Y could typically identify subcontinental regions with a few questions. The observation, then was that Y-chromosome lineages were geographically localized—they tended to define people as coming from a particular place.

While this was fabulously useful to people studying population movements and origins genetically, why it was so was a puzzle. A hypothesis explaining it was suggested in 1998 by Mark Seielstadt, then a student working with Professor Cavalli-Sforza:

Seielstad’s interpretation of these two patterns was that women moved more than men, dispersing their mitrochondrial lineages among neighbouring populations, producing a relatively homogenous mtDNA distribution. The men, meanwhile, stayed at home…

The extent of this ‘staying at home’ is underlined by the fact that some 70 percent of human societies (constituting far more than 70% of the world’s population) practice patrilocality. This means group membership follows the male line; when a woman marries she goes to live with her husband and adopts his clan identity. As a result, a man’s position in a patrilocal society has more to do with who his father was than who his mother was, while a woman’s position has more to do with whom she marries than who either of her parents is. A variety of genetic studies of patrilocal societies have confirmed Mr. Seielstad’s hypothesis that men in these societies inherit a fairly fixed geographic and social position while women have far greater social and geographical mobility. As Mr. Wells notes:

Hindu castes show clear evidence of this pattern, with much greater Y-chromosome than mtDNA divergence between the castes, suggesting that women could move between castes while men were locked into theirs. [emphasis added]

Well, this is a tidy theory and makes sense. However, the male-female differences go beyond this. For example, Y-chromosome markers are not merely geographically localized, they also tend to be quite uniform within a geographical locality. In other words, men in one region will show significantly different Y-chromosome genetic patterns to men from other geographic regions, but they will tend to show very similar genetic patterns to men from their own geographic regions. In other words, a dominant lineage of father-to-son-to-son inheritance in any given locale tends to drive other male-to-male lineages to extinction within a given area.

The same tendency, while observable in women, is weaker. For example, the most recent common female ancestor of humanity—‘Eve’—lived some 160,000 years ago, while the most recent common male ancestor of humanity—‘Adam’—lived only some 60,000 years ago. (Both measures agree on a number of other ‘turning points’ in human history, so this isn’t an artifact of using two different ‘clocks,’ so to speak.) . In short, the dominant lineage of our ancestral Adam wiped out those of other men in 100,000 fewer years than Eve’s lineage accomplished the same trick vis a vis other female-to-female lineages.

It appears that there is a greater tendency for ‘dominant’ male lineages to drive other male lineages out of the game than for dominant female lineages to drive other female lineages out of reproductive existence. Why would this be the case? It would appear that the difference derives from the greater investment of women than men in each child. It is far easier for men to out-reproduce other men than it is for women to out-reproduce other women.

Another way of putting it is that it appears that only a fraction of the male population does all of the reproducing. While this is also true of women, it appears that the ‘active’ fraction of men in reproductive terms is smaller than the ‘active’ fraction of women. According to Mr. Wells:

If there are fewer men than women in a population, then the rate at which Y-chromosome lineages are lost will be greater. But this can’t be true, you might be saying—the birth ratio is 50:50. Surely there are the same number of men and women in every population? Surprisingly, while this is true in terms of numbers [of people], it is not true for the number that pass on their genes by leaving offspring…What we are interested in, then is what is known as the effective population size—the number of breeding men and women. This is where we see the difference.

In short, some men father more children than other men (openly as a result of greater prestige and resources or covertly via adulterous assignations) and if this pattern is repeated over generations the lineage of these over-reproducers will eventually crowd other lineages out.

Unfortunately, Mr. Wells doesn’t offer any data—and he may well not have any—about how long such ‘crowding out’ actually takes, which would allow us to see what percentage of men are actually responsible for society’s reproduction. (Possibly, of course, this could be derived mathematically out of the data he does provide, and I’m just too dumb to be able to work it out.) If it took the full 60,000 years, or 2,500 generations since ‘Adam’ to drive every other lineage out of existence, then the percentage of active reproducers in the male population as a fraction of the total male population must have been quite high. But if it occurred more rapidly than that, then the percentage of the male population reproducing in each generation might be a whole lot less than 100%.

I seem to recall a news story that indicated that huge numbers—literally, tens of millions—of East Asian men are lineally descended from Genghis Khan a mere seven centuries (or 35 generations) ago. That would certainlysuggest that the crowding out of other male lineages by a dominant lineage may occur at a relatively rapid rate.

In any event, all this suggests one more reason why men and women may not see, er, eye-to-eye on social issues. Men (or more properly, their Y-chromosomes) appear to be locked into a reproductive ‘arms race’ with other Y-chromosomes, using wealth, social status, looks, charm, whatever, as weapons. The penalty for failing to outbreed other Y-chromosome lineages into extinction is, of course, that in turn those lineages will outbreed yours into extinction. Hence, men—especially those who are currently ‘winning’ the competition, would see no reason not to drive other men to the wall. As in all forms of mortal combat, notions of ‘fair play’ would be essentially suicidal.

Women (or more specifically, women’s X-chromosomes) on the other hand, seem less invested in such competition, and are able to get by under any regime, so to speak. As a consequence, women, under the guidance of those same X-chromosomes might prefer a social welfare policy that redistributes wealth and makes sure that even those women who marry low-status males will successfully be able to raise their (female) children.

Just in passing, of course, that doesn’t necessarily mean that the women intend to breed with their low-status husbands. Remember that hospital studies of paternity seem to show that at least 10% of children and possibly more are not actually sired by their ostensible father. Not all of the ‘Genghis Khan’ effect comes from men running around forcing women to have children; women’s reproductive strategies would seem to play a role here as well. I suspect being able to say that their children were related to the family of the Great Khan was something a number of women might have considered would be a good move in East Asia 700 years ago.

Likewise, this same X- and Y-chromosome conflict of interest may explain the female-led preference for smaller families in the last 150 years. Women can’t easily run around out-breeding each other, so there may be very little they can do to promote the fortunes of their own descendants in the slower, gentler female reproductive contest. And, if you’re not in a reproductive arms race vis a vis other X chromosomes, and if you have access to contraception, why go to the hassle of mothering larger families?

After all, those extra children chiefly benefit the Y-chromosome in the family, which is locked in its own battle with the other Y-chromosomes in town. And what does an X-chromosome really care about that?

Cheers,

Friedrich

For the story on how Genghis Khan has perhaps 800,000 times more direct male line descendents than the average man alive at his time, here's my article:

http://www.upi.com/view.cfm?StoryID=20030205-100301-1566r

Posted by: Steve Sailer on April 21, 2004 12:53 PM

Thanks, I couldn't find any of those articles. Much appreciated. (I hope I'm remembering them accurately, of course.)

Posted by: Friedrich von Blowhard on April 21, 2004 12:59 PM

I hope this doesn't come across as a wise ass comment, but all my life I've been reading stories about how the dominant males drive the lesser males out of the competitive pool when it comes to all the goodies in life, first and foremost, females; yet when I look around it seems obvious that the overwhelming majority of the population, male (and female), is mediocre in mind and body.
You would think that by now, if the theory was true, we'd all be a race of supermen.
What gives?

Posted by: ricpic on April 21, 2004 5:27 PM

Maybe compared to our hominid ancestors, we are a race of supermen.

I mean, we're the most widely distributed large mammal on the face of the planet--quite a change from 60,000 years ago. We've doubled our average body mass and our lifespan over the past 150 years. I mean, it's not like we lack accomplishments. As regards your comment, I think it comes from having very, very high standards...just the sort of thing you'd expect from a super ape.

Posted by: Friedrich von Blowhard on April 21, 2004 5:34 PM

Uh, we haven't doubled the maximum age of life in the last 150 years--we simply drastically reduced infant mortality and this, in turn, pushed average life expentancy up. Threescore-and-ten still sorta prevails. (Okay, it doesn't quite, but it's close enough to the truth.)

The ratio of males to females at birth in modern societies is about 105 to 100. In grad school at Dear Old Penn they mentioned studies indicating a higher ratio towards conception that was reduced by "wastage", as they put it. Following birth, male mortality rates at all ages are higher than those for females. I'd have to look up the present crossover point where females outnumber males, but in low-mortality countries it should be getting up around age 50.

50,000 years ago, who knows? Chances are, however, that the ratio of males to females at birth might have been 100 to 100 or perhaps 95 to 100, given the likelihood of higher wastage. And given high infant mortality under primitive conditions, females might have outnumbered males at all age groups, the disparity increasing with age.

On the other hand (there's ALWAYS another hand), it is possible that high levels of female mortality duting childbirth could have redressed this possible imablance. We do not know for sure.

End of demography lesson. Thanks for the really interesting article.

Posted by: Donald Pittenger on April 21, 2004 8:05 PM

"Unfortunately, Mr. Wells doesn’t offer any data—and he may well not have any—about how long such ‘crowding out’ actually takes, which would allow us to see what percentage of men are actually responsible for society’s reproduction."

I think about 3 guys I know are responsible for most of it. Ho ho ho.

Posted by: annette on April 22, 2004 2:36 PM

Annette:

Whoa...they sound like busy, busy guys. Do you know if they take anything...vitamin E...shellfish...you know, anything special?

Posted by: Friedrich von Blowhard on April 22, 2004 3:18 PM

Well of course Y chromosomes are able to achieve dominance much quicker than X: in the roughly year or so that it takes from conception to a woman being able to reasonably start another one in the oven, a man can father HUNDREDS of children, at least a couple/few a day if he's in his breeding prime.

A woman of course increases her X chromosome's survival chances by having the most loyal mate with the most resources (read: cash in today's world) that she can find. There are rational issues of genetic survival involved with hot women throwing themselves at even fat/ugly rich men.

It also explains cultures (such as many in Europe) where a woman doesn't care if you have a mistress, so long as we all play pretend that she doesn't exist and you eat dinner/sleep at home. That turns out to be a win-win with both partners genetic survival strategies.

And the Y mutates much more easily that X or mT-dna, which also makes sci-fi scenarios involving loss of fertility due to mutation more realistic. A Y chromosome monoculture with a disastrous flaw after an environmental change is a scary thought. But one that our distant ancestors (if we make it past the 21st Century!) will have to deal with.

Posted by: David Mercer on April 23, 2004 7:12 AM

Mr. Mercer:

I could kiss you. Finally I get somebody who's willing to discuss the heart of the matter. Do you also agree with my admittedly speculative conclusions, to wit:

(a) If we assume that Y's are fighting with other Y's to either dominate or go extinct in a more intensive fashion than X's are fighting with other X's, then it would seem to me that men will be more attached to status-enhancing differences in wealth and less interested in redistribution than women.

(b) If we assume that Y's are fighting with other Y's to either dominate or go extinct in a more intensive fashion than X's are fighting with other X's, then it would seem to me that the advent of widely functional contraception and the knowledge necessary to make it work would empower women to limit family sizes from the male-preferred norms of the 19th-century (7 births per woman) to current norms (of around 1 birth per woman).

It seems to make sense to me, at least as a hypothesis to be tested. (Assuming that someone smarter than me can figure out how to test it, of course.)

Posted by: Friedrich von Blowhard on April 23, 2004 7:42 AM

Well, if it's the desire to battle it out with other Y chormosomes that is behind tax cuts...then men are also the biggest bullshitters ever put on the planet. All this "economic growth for all" falderol. But I suppose being a good bullshitter is part of competing with other Y chomosomes, too. However, being a Democrat did not seem to hurt Bill or JFK's ability to exercise their Y chromosomes. If women want redistribution, then wouldn't it make sense for men who want to spread their Y chromosomes around, to take an interest in redistribution and score more with women??

Posted by: annette on April 23, 2004 11:28 AM

You X and Y theorists might enjoy this posting from Alex Taborrok about how gals and guys compete, here.

Posted by: Michael Blowhard on April 23, 2004 11:50 AM

Annette:

Of course being able to bullshit is a fabulous weapon in the Y vs Y game. I also note that advocating greater income equality on the parts of JFK and Mr. Clinton didn't seem to preclude them from either staying or getting rich. Ah, the fabulous odor of fertilizer.

Posted by: Friedrich von Blowhard on April 23, 2004 12:48 PM

To smudge the picture up a bit: what do y'all make of the fact that a guy who wants to have, er, a little fun with a gal had better learn how to say at least a few of the things a gal likes hearin'? And maybe he should learn how to sound like he means it too. Does this complicate the equations at all? I mean, I don't know too, too many guys who succeed with women via sword-waving, chest-pounding, and standing for things women don't approve of. Well, OK, that's been my personal, highly-successful method. But don't most guys learn that one way of proving their fitness is by showing that they're man enough to respect (and, to some extent, serve) a woman's needs and preferences? Plus, at the same time, show off a little incorrigible bad-boy charm?

Lordy, it ain't easy.

Posted by: Michael Blowhard on April 23, 2004 12:58 PM

Michael:

I didn't say that Y vs. Y competition is based on sword waving, chest thumping, and saying things women don't want to hear. (Although life might be a lot more entertaining if it were.) But I don't know too many women who regard a guy with bucks and a determination to make a lot more so as to have the wherewithal to raise a family as a liability...at least not women over the age of twenty. Not to be cynical or anything, but as I got a bit older and had some dough and started dressing like it I mysteriously got a lot better looking. Of course, burping less often, bathing regularly and complimenting women on their shoes helped too. Go figure.

Posted by: Friedrich von Blowhard on April 23, 2004 2:43 PM

FvB, I'd certainly agree with both of those propositions. If men were all fairly uniform financially due to redistribution, they would engage in other, perhaps more silly, displays to signal the suitability of their genes to women. They don't say "he's dressed like a peacock" for nothing!

And while The Pill (and other advanced contraception technology) might gain women more in reproductive genetic terms, it sure as hell let's men trick their glands into thinking they've reproduced a lot more often than they have (go team! :-)

Posted by: David Mercer on April 24, 2004 3:30 AM






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