Saturday, December 12, 2009

Asia populated in one migratory swoop

By David Cyranoski

Researchers mapping a massive array of genomes across Asia say they have found evidence that humans covered the continent in a single migratory wave, and share a common ancestry.

The findings were released by the Human Genome Organisation (HUGO) Pan-Asian SNP Consortium which looks at single-nucleotide polymorphisms (SNPs), or variations at individual bases that make up the genetic code. The results challenge the view that Asia was populated by at least two waves of migration.

"In Asia, we are all related," says Edison Liu, a lead author from the Genome Institute of Singapore. "It brings us closer together."

It is thought that a wave of humans emerged from Africa some 60,000-75,000 years ago and travelled along the southern coast of India, into southeast Asia and down to Oceania. But scientists struggled to explain some of the variation seen in Asia today - such as the obvious physical differences between Malaysian and Filipino Negrito populations and other Asians. Some researchers have postulated that a second wave, or series of waves, from a northern route largely repopulated the area, leaving the Negrito and others as relicts of the earlier migration.

The new study, a five-year examination of variation at some 55,000 SNPs in 1928 individuals, found that Negrito populations had a high level of genetic overlap with other southeast Asia populations, suggesting a common ancestry. East Asians, the analysis suggests, share a large degree of common genetic background with southeast Asians but very little with central Asians, seeming to preclude a peopling of east Asia through a northern route via the Eurasian Steppes. And genetic variation within local populations decreased from southeast to northeast Asia. The two observations suggest that diverse peoples living in southeast Asia migrated northwards.

"It's an impressive collection of samples, a huge amount of work and analysis, and it will contribute greatly to the field," says Mark Stoneking, an evolutionary geneticist at Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who was not involved in the study.

Asian unity

Merely organizing the work was a massive task. Researchers in 11 countries and regions took samples from 73 populations, requiring countries often at political or economic loggerheads to share ideas, technology and genomes. For countries lacking the technological capabilities to do the genetic analysis but loath to ship genetic samples to another country, Liu established a system by which researchers could bring the samples to host countries and do the studies themselves, in collaboration with their hosts. "The chain of custody was never broken," he says. "It was extraordinarily collegial."

The result is not a complete shock. While this study provides the most detailed analysis of genetic diversity among Asians to date, a 2005 study on mitochondrial DNA came to a similar conclusion2. Martin Richards, at the University of Leeds, UK, is a specialist in genetic variation in southeast Asia who led that study. "By and large, [the new study] is not surprising for fans of mitochondrial DNA, I think, but naturally it is very heart-warming," he says.

The new study also supports mitochondrial DNA evidence that challenges the customary "out of Taiwan" model, in which migration from mainland China through Taiwan led to the settlement of southeast Asia and the Pacific islands. Instead it seems Taiwan may have been largely settled from islands in southeast Asia.

But the results are not conclusive, as the authors admit. Stoneking says he was "very surprised that the Negrito populations were not more genetically distinct", and would like to see other supposed relict populations, such as those in New Guinea and Australia, studied in the same kind of detail. He argues that it is not possible to tell whether extensive genetic intermingling with surrounding populations might have obscured evidence for two waves of migration. He says he has evidence to support the two-wave theory in work yet to be published that looks specifically at mitochondrial DNA and Y-chromosomes of Negrito populations.

Liu says he is discussing plans for a second phase study with much higher resolution - based on 600,000-1 million SNPs. Possible extensions for the new project will be a look at copy number variation (duplications in sections of DNA), a resequencing of mitochondrial DNA and a focus on specific genetic components such as differences between enzymes that metabolize drugs, and human leukocyte antigen variations. It will be especially tantalizing, says Liu, to see if drug-metabolism genes show the same north-south variation in east Asia. "There would be implications for drug response and clinical trials," he says - although he adds that it will not be possible to link specific health information to genotypes across the continent.

Asia populated in one migratory swoop - SciAm
http://www.sciencemag.org/cgi/content/abstract/326/5959/1541
 

6 comments:

  1. There is a perfect correspondence with the haplotype picture of MNOPS expanding out of SEA, with P in Bengal and R as pan-indian with subsequent gypsy-like spread of R into the North. But our aryanwalas will never give up their fantasy life of S Asians and SE Asians as 'hybrids' between steppe herrenvolk and tropical "negritos". I suspect there is a trace of 'negrito hatred' at work here, in addition to the usual.

    A major pillar has fallen with both dark-Caucasoids and dark-Mongoloids (floabt)as ancestral to their northern derivatives. The herrenvolk have now even started roping in their G2 keeps to do some sepoy work (with the usual affected indignance, of course). I have nothing against the G2 keeps, but they should not assist the herrenvolk, especially after their 19th century "experience".

    As usual, enjoy the tamasha.

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  2. now these jokers have started to attack the significance of diversity. unfortunately, phylogeny is a brick wall.

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  3. They can't handle the truth. We'll see a lot more of this happening. DNA forums are very low in activity of late. Pretty soon they will be arguing about who belongs in which block of their neighborhood. Such is the way of misguided reductionism (albeit a very juvenile variety).

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  4. Boss, you will see these fellows suddenly mutate into agnostics. Silence will suddenly signify that the question itself is nonsensical, a la Buddha. Admission of defeat? nah never, we are beyond such silly considerations. Trivialization of the pursuit will replace trivialization of the colonized's experience and the colonized's feeble remonstrations. Much easier than ackowledging one's crimes, wrong nature, and bullheaded conjectures now etched in stone. Pan-eurasian Herrenvolk frolics? Not interested. Not me. We've previously penned umpteen tomes on euro supremacy, you say? Aha, but I am who I say I am, will to power y'know, and I say I'm uninterested. No thankee, you snake oil wala.

    But these civilizational scale sour grapes will not be digested easily. A new monotheism may even spring forth after a hitler type makes a desperate dash for renewed gravitas. It is quite possible. At least keep one's eyes open.

    But in the meanwhile, enjoy the flood of overnight agnostics and hermit babas

    Cheers

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  5. I see the trend of trivializing the pursuit already taking place. Like you've noticed - first it was frequency and now diversity doesn't matter anymore to them. 'Who cares about that, we're more interested in our unique haplogroup clusters' - I hear this very often,and - 'we might as well accept that we all came from Africa, we're not interested in South Asia'. I wonder why they're interested in DNA at all now! They might as well check out Botany Bay and Ellis island records and be content with that I say. Oh, and of course, let's not forget the whole unprovable argument of IE language origin - that's keeping them very very busy nowadays.

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  6. Boss,

    I think, with AIT, these guys overreached way beyond the capabilities of Monotheism.

    Monotheism is quite suited to appropriating a Buddha here, an Ashoka there, a Skanda as Alexander, or a Devadutta as Diodotus. It can be empirically distinguished from typical heathen cross-identification by the presence of imperialist impulses. Thus while the manufacture of Jesus' identity with the Emperor resulted in the desired emasculation of the Sicarii revolt, an Ayutthaya in SEA never elicited a threat perception from the 'natives' (if they can be so deemed in our heathen reality).

    But for the monotheist colonizer to (logically) maintain such point appropriations, it is also necessary (for some reason) to appropriate, or otherwise transform, whole 'histories' of peoples. Judaism was one such attempt in the case of Christianity, and AIT was another in the case of India. Judaism resulted in the target becoming a haggard shell, but AIT could never be similarly ramrodded through. It is our task to analyze why they failed in our case; and it has much more to do with our unique strengths than just heathens outfoxing the colonizer at its own game or the heathen memory surviving in numbers.

    We will see these guys increasingly assume a pseudo-heathen stance of 'indifference'. The fruit of five centuries of "academic" tamashagiri, stealing manuscripts, forging false narratives and interpretations, was to, in the end, become "sour grape heathens" affecting a culled attitude of indifference. What a bitter reward for an uber-ideologically-motivated "people," simultaneous rugged individualists and team players (by "principle", of course ------ 'as the situation demands' is way too heathen, too asiatic mode of production, too gypsy).

    As they say, to kill one person is 'murder' while to genocide off entire peoples is "liberation of the land". Monotheism is just the opposite: appropriation of one personality, ok, it can pass in most instances; but to appropriate entire peoples takes much more ingenuity than that displayed by the anglo heirs to the christist believers.

    And to think that, most of the time, these guys lose to their own fellows who are more honest in their "assessments" but who nonetheless swear by the sacred theory. To be done in by the naive and insufficiently socialized compatriot, hey, that is the heathen destiny, not our uber self blazened path of Individualist Empire.

    It was a good run.

    Yawn..

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