Gene Expression

After reading Genetic Discontinuity Between Local Hunter-Gatherers and Central Europe’s First Farmers I’m left scratching my head a bit. Cut-out black & white models really benefit from lack of data, and now that there’s some serious data I think perhaps that we need to think about starting from a clean slate in many ways. The title of the article is rather justified in the local contexts: on the mitochondrial DNA (female lineage) there is an enormous difference between farming and non-farming populations. Here are the locations of these samples:

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The genetic disance seems to have been 5-6 times greater than between modern European populations. Additionally, modern Europeans are very different from both these prehistoric samples (though somewhat more distance from the hunter-gatherers than farmers).

One of the major reasons for this difference is the very high frequency of haplogroup U among the hunter-gatherers, in particular the subclade U5. This lineage is still around, in fact it was labelled “Ursula” in Bryan Sykes’ The Seven Daughters of Eve: The Science That Reveals Our Genetic Ancestry, the earliest European lineage. It would seem though that this lineage was far more frequent after the Ice Age than Sykes’ model would have predicted. In The Real Eve: : Modern Man’s Journey Out of Africa the author asserts that most of the genetic variation we see around us was already fixed by the Last Glacial Maximum, and these data would strong suggest that that extreme model is falsified.

Today the frequency of U5 exhibits a south-north cline in increased frequency in Europe, as noted in the text of the paper:

Europeans today have moderate frequencies of U5 types, ranging from about 1-5% along the Mediterranean coastline to 5-7% in most core European areas, and rising to 10-20% in northeastern European Uralic-speakers, with a maximum of over 40% in the Scandinavian Saami.

Does this then mean that the Uralic peoples of northern Europe, in particular the Saami, are the exemplars of Ice Age European man? Perhaps. But it is also true that populations change over time, so even if the Saami have more in common in terms of their ancestry with the pre-Neolithic peoples of Europe, they may have changed a great deal in terms of their traits over the past 10,000 years. Finally, it may be that a particular non-agricultural lifestyle may select for particular mtDNA lineages! Or, perhaps the U haplogroup confers advantages in colder climates, selective pressures which were naturally relaxed after the last Ice Age. These sorts of muddled confounds have to be entertained, especially in light of the fact that the farmers who were contemporaneous with the European hunter-gatherers seem different from modern Europeans.

That leaves us with the reality that a parsimonious model with a few simple historical-demographic parameters may not explain the variation of genes in modern Europe, or in much of the world. But why should we expect such simplicity in the past when we don’t have it today? Consider this map of China, which greatly simplifies, but illustrates that as the Han spread south of the Yangtze they settled the bottom-lands first and left the less arable regions for native peoples. Farming does not spread on a wave of advance as the crow flies, but rather percolates like water, seeking out rich soils and favorable climates. This would especially be the case as one pushes in new lands where one’s crop toolkit may not be optimized in the first place. The archaeology in Europe suggests this occurred as farmers pushed north of the Alps and up the Danubian river systems, pockets of agriculture slowly expanded outward into less favored lands. This sort of spatial topology does not lend itself to succinct verbal treatments, or perhaps even elegant mathematical ones.

Cite: Science DOI: 10.1126/science.1176869

Comments

  1. #1 frog
    September 4, 2009

    “This sort of spatial topology does not lend itself to succinct verbal treatments, or perhaps even elegant mathematical ones.”

    Depends on your manifold — you can make the treatment simple if you bury it as part of the underlying surface. Then the math can be simple — but with a nasty input.

    But nothing interesting lends itself to succinct verbal treatments.

  2. #2 razib
    September 4, 2009

    frog, i wondered if i would get a response like that in the comments. duly correct ;-)

  3. #3 Jean
    September 5, 2009

    The Uralic-speaking people arrived in northern Europe far later than the Mesolithic and may be linked to Y-DNA haplogroup N1c in the Saami. Their predominant mtDNA haplogroup is U5b1b1, which is similar to U5b1b found among Berbers, so we can guess that it spread both ways from the Iberian Ice Age refugium.

    I was amused by the scratching of heads that went on among the researchers when they realised that the present population of Europe is not a simple matter of Mesolithic + Neolithic input. Linguists have been saying for decades that the Indo-European languages spread across Europe in the Copper/Bronze Ages. Several geneticists have linked Y-DNA R1a1 with this. R1b1+ seems to be the other half of the story, as I argue in my online article: The Peopling of Europe.

  4. #4 Alan Kellogg
    September 5, 2009

    It’s really very simple…

    First the goblins out competed the ogres and drove them into extinction. Later the elves invaded with their brand new agriculture and drove the goblins into extinction. Finally, humans encroached on elven lands with new technologies and largely supplanted the elves. It all becomes so much easier to understand when you know of the secret history.

  5. #5 Otto1923
    September 6, 2009

    Otto finds new pastures to lie down in…

    ” 4 The Nephilim were on the earth in those days. That was when the sons of God went to the daughters of men and had children by them. The Nephilim were the heroes of long ago. They were famous men.”
    -And ye, the hunters and gatherers gazed down into the valley below and saw the farmers with their stores of food and their comely daughters, and realized they had found new prey.

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