Men on the move, part n

By Razib Khan | November 1, 2011 3:28 am

Ancient DNA suggests the leading role played by men in the Neolithic dissemination:

The impact of the Neolithic dispersal on the western European populations is subject to continuing debate. To trace and date genetic lineages potentially brought during this transition and so understand the origin of the gene pool of current populations, we studied DNA extracted from human remains excavated in a Spanish funeral cave dating from the beginning of the fifth millennium B.C. Thanks to a “multimarkers” approach based on the analysis of mitochondrial and nuclear DNA (autosomes and Y-chromosome), we obtained information on the early Neolithic funeral practices and on the biogeographical origin of the inhumed individuals. No close kinship was detected. Maternal haplogroups found are consistent with pre-Neolithic settlement, whereas the Y-chromosomal analyses permitted confirmation of the existence in Spain approximately 7,000 y ago of two haplogroups previously associated with the Neolithic transition: G2a and E1b1b1a1b. These results are highly consistent with those previously found in Neolithic individuals from French Late Neolithic individuals, indicating a surprising temporal genetic homogeneity in these groups. The high frequency of G2a in Neolithic samples in western Europe could suggest, furthermore, that the role of men during Neolithic dispersal could be greater than currently estimated.

Some notes:


Otzi the Iceman is G2a.

– A continuity of local maternal lineages would not be so surprising. Recall that ~50% of Argentine mtDNA seems to be indigenous, even though they’re ~80% European in total ancestry, and ~95% European in the paternal line.

– This is not limited to Latin America. In South Asia the majority of the maternal lineages are non-West Eurasian, while the majority of paternal lineages are West Eurasian. Autosomal ancestry seems to be about half West Eurasian.

– There are now several instances of Neolithic settlements yielding relatively rare paternal lineages, which are almost certainly intrusive, but left little impact. The authors step forward with the most plausible, and frankly suprising, rationale:

The high frequency of G2a haplogroup in Neolithic specimens, whereas this haplogroup is very rare in current populations, also suggests that men could have played a particularly important role in the Neolithic dissemination that is no longer visible today. This would imply that intra-European migrations related to the metal ages may have strongly affected the modern
gene pool.

In other words, the European paternal lineage landscape may not be determined primarily by the hunter-gatherers or first farmers, but subsequent groups. The relative lack of the two dominant European haplogroups, R1a and R1b, is particularly notable. What’s going on? Perhaps male lineages were “winner-take-all,” and have a tendency to rise to near fixation and then shift toward extinction, more than female lineages? The Genghis Khan haplotype story may be less exceptional than we think. If this is right then we need to be very careful about the historical lessons we draw from mtDNA and Y chromosomes, because they may give us a skewed and unrepresentative picture of the demographics of the past.

CATEGORIZED UNDER: Agriculture, Genetics, Genomics
  • Eurologist

    Note, it said “intra-European”.

    My model has been such: much of LBK, and parts of Cardium, derive from the happenstance haplogroups present in the Balkans and middle Danube at the time. A smaller fraction (~10-20%?) is directly Anatolian, and some groups (like G2) are of course originally Black Sea/ Anatolia, except they were already present in the Balkans pre-neolithic, due to easy travel routes and established contacts. This explains the relative paucity of J and E.

    Then, at the fringes, other haplogroups got integrated. LBK was a furiously-expanding, thinly-populated “bubble,” and following its collapse, its haplogroups were largely (but not completely) replaced by those of the populations at the fringes. And those were R1b in the West, and R1a in the East. There is no need to involve any type of mass migrations, which became exceedingly difficult after agriculture, in any case.

    Of course, E1b1b1a1b is also centered around the northern Balkans…

  • Bob Dole
  • http://washparkprophet.blogspot.com ohwilleke

    The ancient DNA evidence may provide some approximation of the time depth of coherent population genetic communities in places like the Caucasus Mountains that still have relatively percentages of G2a.

    It also tends to establish that the Basque, who are 87% Y-DNA R1b-M269 and also have very high levels of the European version of the lactose tolerance gene. Both appear to have been intrusive to Southern Europe and Iberia vis-a-vis the first Neolithic populations (or in the case of R1b-M259, but not lactose tolerance, alternately indigenous but not incorporated in this Neolithic wave). This suggests that they are probably not appropriately associated with the Cardial Pottery Neolithic migration wave, and the high levels of lactose tolerance suggests that they did not arrive in their current refugia location until later than the Cardial Pottery culture (the Gascons, with low lactose tolerance are better candidates for Paleolithic descendants) although they seem to have obviously preceded the Indo-European migration into Iberia.

    This puts a moderately tight time band on this population and seems to disfavor linguistically driven Basque-Caucasian correlations. Although is does more to rule out points of origin for this cultural and linguistic community prior to its establishment in Iberia than it does to point out likely points of origins of connections to other known pre-Indo-European cultures.

    It is also worth noting that while we have a pretty good sense of the mtDNA makeup of Europe in the Upper Paleolithic, that we have virtually no Upper Paleolithic Y-DNA samples. We can be confident that they were somewhere a part of Y-DNA macrohaplogroup F and can rule out some of its descendants (e.g. H), but not much more.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    #3, i think lactose is a pretty bad locus to use to measure demographic processes, because it is under such strong selection.

  • http://www.astraean.com/borderwars/ Christopher@BorderWars

    European G2a represent!

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    There is no need to involve any type of mass migrations, which became exceedingly difficult after agriculture, in any case.

    this is my instinct too. and yet david reich’s lab does seem to indicate that the preponderant ANI element post-dates the first farmers in south asia by thousands of years! i’m not willing to accept this yet, but my incredulity at mass replacement after agriculture is mitigated somewhat of late….

  • Dwight E. Howell

    If a group of males gain complete control of a region they will have access to the most desirable females, can father the most sons, or at the least have the most sons grow up and have sons. The children of the poor and outcasts often lack access to the necessities of life.

  • Eurologist

    “david reich’s lab does seem to indicate that the preponderant ANI element post-dates the first farmers in south asia by thousands of years!”

    I must have missed that one – still skeptical, though, since I think part of the split is native to the subcontinent, and predates LGM by a factor of 2-3…

    “If a group of males…”

    Yes, of course, that explains e.g. why y-DNA is such a lousy indicator of autosomal. But more often than not, we find that such post-neolithic y-DNA intrusions (that are not also accompanied by thousands of year of technology difference or biological warfare) peter out with just marginal signatures left (Hungary, Turkey, much of the Slavic fringes, the original Franks, Romans in North Africa or pretty much elsewhere, etc.).

  • http://washparkprophet.blogspot.com ohwilleke

    #4, the selection pressure on lactose tolerance on Mediterranean Europe can’t be very great, because the most lactose tolerant population in Europe (the Basque) and some of the least lactose tolerant populations in Europe (e.g. the Gascons) live about a hundred miles apart. The LT selective pressures are predominantly north of the olive oil-butter line in Europe.

    One can draw reasonably strong inferences about Basque prehistory from these facts because (1) direct evidence from ancient DNA shows that Cardial Pottery Neolithic farmers predominantly weren’t lactose tolerant, (2) a wealth of archeology shows CP Neolithic to be the first food producing population in the region, and (3) there is apparant lack of selective pressure on lactose tolerance in this geographic vicinity.

    Honestly, Y-DNA is probably less informative than LT, because the Y-DNA mix is relatively homogeneous over quite large geographic regions compared to LT which varies a great deal within Europe at a fairly fine grained level. Even when gets into very detailed subhaplogroups of R1b, the resolution doesn’t get much finer than breaking Western Europe into three or four chunks (Scandinanvia, British Isles and Brittany, SW Europe and the greater Alpine region).

    There is also less certainty over when R1b expanded due to inherent flaws in Y-DNA dating (the mutation rate varies by a factor of three between different methods and the mutation rate also varies materially from one locus to another) and a thin ancient DNA set for Y-DNA relative to LT genes which have a richer ancient DNA set and a much better motivated connection with known events in prehistory (the rise of dairy farming) that can be coroborated from historical evidence. The fact that LT is subject to selective pressure rules out dates for its emergence that far precede dairy farming (e.g. the Upper Paleolithic and earliest Neolithic) and also dates for its emergence that far post-date the emergence of dairy farming (e.g. post-Bronze Age collapse).

    Unless the Basque founding population was very, very small or involved a very small number of large but inbred extended families, its origins have to be sometime between 4600 BCE and 1300 BCE (linquistic considerations push the second date further back, narrowing the range), and have to have been from the North in Europe rather than via Mediterranean sea transport, given LT considerations alone. Autosomal genetics reinforces the lack of a Mediterranean sea transport origin. Once framed by these parameters, the uniparental genetic data can tell a clearer story.

    For the Basque, the cofound is not LT genetics due to selection, but RH negative cofounds due to selection. High RH negative blood type levels form an invisible barrier to admixture with neighboring populations that make inferrences drawn from populations not inherently resistent to admixture less reliable.

  • Justin Giancola

    “the olive oil-butter line” coin this. ha ha

  • http://washparkprophet.blogspot.com ohwilleke

    @10

    Not an original turn of phrase from me. See e.g., in 2007, references at the BBC and this blog from 2007, and in the body of a 1992 paper on folklore. There is a closely aligned “wine/beer” line in Europe as well. The parallel to the Catholic/Protestant line in Europe is there as well, although not nearly as strongly overlapping.

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About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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