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SEVEN hundred and forty centuries ago, give or take a few, the skies darkened and the Earth caught a cold. Toba, a volcano in Sumatra, had exploded with the sort of eruptive force that convulses the planet only once every few million years. The skies stayed dark for six years, so much dust did the eruption throw into the atmosphere. It was a dismal time to be alive and, if Stanley Ambrose of the University of Illinois is right, the chances were you would be dead soon. In particular, the population of one species, known to modern science as Homo sapiens, plummeted to perhaps 2,000 individuals.

This survey will ... ask how these apes not only survived but prospered, until the time came when one of them could weave together strands of evidence from fields as disparate as geology and genetics, and conclude that his ancestors had gone through a genetic bottleneck caused by a geological catastrophe.

Not all of his contemporaries agree with Dr Ambrose about Toba's effect on humanity. The eruption certainly happened, but there is less consensus about his suggestion that it helped form the basis for what are now known as humanity's racial divisions, by breaking Homo sapiens into small groups whose random physical quirks were preserved in different places.

The idea is not, however, absurd. It is based on a piece of evolutionary theory called the founder effect, which shows how the isolation of small populations from larger ones can accelerate evolutionary change, because a small population's average characteristics are likely to differ from those of the larger group from which it is drawn. Like much evolutionary theory, this is just applied common sense. But only recently has such common sense been applied systematically to areas of anthropology that have traditionally ignored it and sometimes resisted it. The result, when combined with new techniques of genetic analysis, has been a revolution in the understanding of humanity's past.

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in the Economist, http://www.economist.com/opinion/displaystory.cfm?story_id=5299220&no_na_tran=1

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Originally posted by maestro:
Unfortunately for this analysis, the differences between 'races' is swamped by differences between individuals. This has been shown to be true over and over, but for some reason fails to 'catch'.

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Your point (which was one of mine too) he calls a fallacy -- the extremes of variation exist in every large category of people, yes, but the correlations of traits do vary with the groupings we used to call racial. Which of course is common sense.

However, I don't think the theory starting this thread has anything to do with that.

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Originally posted by Yst:

You seem to have pretty much entirely distracted yourself from the thrust of the article and interview by instead reciting an irrelevant truism, accompanied by nothing to associate it with the linked story. I don't really understand the logic of this.

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I had just read the obituary of William W. Howells, who had spent a lifetime measuring differences of local homogenous populations.

I was responding to this paragraph in the posted article:

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Not all of his contemporaries agree with Dr Ambrose about Toba's effect on humanity. The eruption certainly happened, but there is less consensus about his suggestion that it helped form the basis for what are now known as humanity's racial divisions, by breaking Homo sapiens into small groups whose random physical quirks were preserved in different places.

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According to Howells, whose research is cited to this day:

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His data came from specimens representing local populations of unusual homogeneity, and his analysis of the measurements he collected indicated to him that the variations within these groups far exceeded the variations distinguishing group from group.

The evidence from his research bolstered the proposition that all modern humans are of one homogeneous species, whereas earlier humans, even very recent relatives like the Neanderthals, differed from them as distinctly alien species.

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In other words, those 'random physical quirks' which the original post says were 'preserved in different places', and which are cited as being the basis for 'humanity's racial divisions' are swamped by differences between individuals.

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Originally posted by bigcitygal:
Um, Makwa, I don't think I've said this for a while but: you rock and I love ya, dude!

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organ rejections by different individuals of various racial groups are not socially constructed -- they are medically constructed, an element of physiology

this complicated picture will rarely be resolved by preconceptions a la babble

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Originally posted by Geneva:
let me interrupt this love-in to add:
thousands of centuries of physical separation may reasonably have produced ethnic physical differences;
ethnic particularities may well be socially constructed ; but no analysis to date is conclusive

organ rejections by different individuals of various racial groups are not socially constructed -- they are medically constructed, an element of physiology

this complicated picture will rarely be resolved by preconceptions a la babble

any medical/physiological experts around?
none I can see ...

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The person I mentioned William W. Howells was exactly the expert you were asking for.

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Originally posted by maestro:
Unfortunately for this analysis, the differences between 'races' is swamped by differences between individuals. This has been shown to be true over and over, but for some reason fails to 'catch'.

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... and sometimes differences between large ethnic groups (races) swamp individual differences, with life and death consequences:
http://www.shareyourlife.org/africanamerican/

Transplant success rates increase when organs are matched between members of the same ethnic and racial group. For example, any patient is less likely to reject a kidney if it is donated by an individual who is genetically similar. Generally, people are genetically more similar to people of their own ethnicity or race than to people of other races. Therefore, a lack of organs donated by minorities can contribute to death and longer waiting periods for transplants for minorities.

... hence the much longer waiting times for African Americans to get some transplants, because the rate of organ donation is lower in that group and hence fewer acceptable transplants;

so, for some concrete medical situations, people are quite distinct in key ways from other ethnic, whatever, lineages

this is not "socially constructed", au contraire, it is an intrinsic genetic difference that probably evolved over time between large discrete groups of people

.

[ 06 January 2006: Message edited by: Geneva ]

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Originally posted by Fidel:
Or wrt Lucy, meet my black mama ?. ha ha

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Originally posted by Geneva:

... and sometimes differences between large ethnic groups (races) swamp individual differences, with life and death consequences:
http://www.shareyourlife.org/africanamerican/

Transplant success rates increase when organs are matched between members of the same ethnic and racial group. For example, any patient is less likely to reject a kidney if it is donated by an individual who is genetically similar. Generally, people are genetically more similar to people of their own ethnicity or race than to people of other races. Therefore, a lack of organs donated by minorities can contribute to death and longer waiting periods for transplants for minorities.

... hence the much longer waiting times for African Americans to get some transplants, because the rate of organ donation is lower in that group and hence fewer acceptable transplants;

so, for some concrete medical situations, people are quite distinct in key ways from other ethnic, whatever, lineages

this is not "socially constructed", au contraire, it is an intrinsic genetic difference that probably evolved over time between large discrete groups of people

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[ 06 January 2006: Message edited by: Geneva ]

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Well, I suppose I could ask you to define what is meant by 'race', but what would be the point. You already believe the hogwash about 'large discrete groups of people'. Where are these large groups of discrete people you're speaking of. Certainly not in the US, where 'racial' mixing has been going on for three hundred years.

The issue of organ transplants and ethnicity has nothing to do with 'race'. It has to do with tissue type. The closer someone is to you in tissue type, the more likely an organ transplant will work.

Obviously, the best chance of having a transplant take is if the donor is in the immediate family. The further from that immediate family, the less likely the transplant will work.

Given there are groups around the world that are relatively isolated, it is no surprise that matching tissue type would be easier with someone in that isolated group.

The thing to remember is that just because someone is of a particular ethnic group, that doesn't mean they will automatically be able to match tissue with another of that group. As well, just because two people are of different ethnic groups doesn't mean they can't match tissue type.

In other words, there is no hard and fast ethnic or racial demarcation point which guarantees a tissue type match.

Here's a good article on tissue matching and ethnicity:

Code of Many Colors

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Subspecies, or races, exist for many animals—for example, the alleles in some populations of grey wolves score up to 70 percent on the F-statistic scale. However, the groups of people considered to be of different races have allelic differences of at most 15 percent, too little to constitute subspecies.

...In tissue matching, a bastion of genetic differences between people, Dunston finds that race is not the determining factor. "We have this thinking in America that there are some deep differences in biology between whites and blacks, that tissue in whites is more similar to [tissue in] whites than tissue in blacks," she says. "But when we look at the genetics, because of the tremendous variation in all groups, and especially in the group called 'black,' it's not uncommon at all to find two blacks who could be very different from each other."

In some cases, a black organ donor, Dunston adds, can better match a white recipient than a black one.

...Rather than there being clear racial lines, says Shriver, "there's really a continuum of variation across the globe." If researchers sampled only people in Africa and Sweden, the genetic differences between the two groups would be striking. However, a sampling of people from Africa, Sweden, and everywhere in between would reveal only small differences between each population and its neighbors. "You won't see a place where you'll say, 'There's the racial divide,'" says Shriver.

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