Given my R1b1b2 male-line YDNA results, I thought that it was safe to claim a long shared history, with the descendants of the Mammoth Hunters who roamed north as glacial melting gave way on the Atlantic edges of Europe to moist, steppe grasslands teaming with big game.
And that it was not hard to imagine these people become cattle and sheep herders in later periods, riding rough-legged Welsh or Irish-type ponies – and becoming raiders and reivers when opportunity presented.
The theory or perhaps myth propagated by genetic analysts like Bryan Sykes and Stephen Oppenheimer was that the 60 to 70 percent of the males of the British Isles who carry the R1b1b2 haplotype stemmed from small bands of hunters who had holed up behind the Pyrenees.
After the melt, the story goes, they parted company with their Basque and Catalonian forbears, following the burgeoning herds of game north, eventually penetrating as far as north western Ireland, where they account for virtually 100 percent of the male population.
This made it possible to claim that these ‘Atlantic’ people were the original / aboriginal inhabitants of the British Isles (discounting previous inter-glacial population episodes).
It also suggested that the Indo-European languages were adopted by the descendants of the Atlantics, as cultivation spread west from its hearth in Asia Minor. The slow western diffusion of cultivation was further held to explain the gradual strengthening of the R1b1b2 gene pool along the line drawn between Connaught and the Balkans, as the eastern pioneering spirit faded and the new techniques were more readily adopted and promoted by the ‘natives’.
This left the Basque language as a lone outlier of a language group that once served all the Atlantic peoples – and as a relic of our hunter-gatherer past in north-western Europe.
But just as we can never be entirely sure of our ancestors (given ‘non-paternal events’, name changes etc.), so we can never be entirely certain that one explanation best fits the currently known facts about prehistory.
An alternative view is that R1b1b2 is the most common form of male-line YDNA in the western fringes of Europe because it records the relatively recent breeding successes of small bands of farmer cultivators, who represent the late, leading edge of a long-standing influx into the European Peninsula, which originated in Asia Minor.
This interpretation has been backed by an intensive study recently reported in the journal Plos Biology.
It is consistent with a couple of well-established trends. The first is for genetic variation to be much more intense in the core or originating home of a diffusing population (the considerable differentiation of DNA within Africa, as contrasted with the relative uniformity of non-African DNA is the prime example).
The second trend is for small populations to rise rapidly when they reach new resources – new ‘resources’ either in the form of previously un-hunted or untilled areas. When cultivation was first introduced into north-western Europe, the rewards and surpluses were comparatively great (hence the availability of food to fuel the construction of megaliths) – and the survival rates of children and the more vulnerable members of society massively improved.
As Steve Connor of the UK Independent puts it:
‘They came, they saw, they farmed and then they stole our women. Stone age farmers from the middle east not only brought their agricultural know-how with them to western Europe, they settled down with the local womenfolk and had children’.
According to a spokeswoman for the study team, Dr Balaresque:
“In total, this means that more than 80 per cent of European Y chomosomes descend from incoming farmers. In contrast, most maternal genetic lineages seem to descend from hunter-gatherers.
To us, this suggests a reproductive advantage for farming males over indigenous hunter-gatherer males during the switch from hunting and gathering to farming – maybe, back then, it was just sexier to be a farmer”.
This leaves two questions:
• Were the maternal ancestors of most of us more closely related to the peoples of North Africa?
• How can we explain the peculiar status of Basque as an outlier among Europe’s Indo-European languages? Perhaps there too, we should look south.
FOR FOLLOW UP - SEE:
‘How settler farmers fathered Europe's males’ by Steve Connor, Science Editor, UK Independent, Tuesday, 19 January 2010
‘Most European males 'descended from farmers'’ by Paul Rincon, BBC News, at: Paul.Rincon-INTERNET@bbc.co.uk
‘A Predominantly Neolithic Origin for European Paternal Lineages’ by Patricia Balaresque, Georgina R. Bowden, Susan M. Adams, Ho-Yee Leung, Turi E. King, Zoë H. Rosser, Jane Goodwin, Jean-Paul Moisan, Christelle Richard, Ann Millward, Andrew G. Demaine, Guido Barbujani, Carlo Previderè, Ian J. Wilson, Chris Tyler-Smith Mark A. Jobling, Plos Biology Journal, January 2010 at: http://www.plosbiology.org/article/info:doi%2F10.1371%2Fjournal.pbio.1000285
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Extracts from the Plos Biology Paper:
Abstract
The relative contributions to modern European populations of Paleolithic hunter-gatherers and Neolithic farmers from the Near East have been intensely debated.
Haplogroup R1b1b2 (R-M269) is the commonest European Y-chromosomal lineage, increasing in frequency from east to west, and carried by 110 million European men. Previous studies suggested a Paleolithic origin, but here we show that the geographical distribution of its microsatellite diversity is best explained by spread from a single source in the Near East via Anatolia during the Neolithic.
Taken with evidence on the origins of other haplogroups, this indicates that most European Y chromosomes originate in the Neolithic expansion. This reinterpretation makes Europe a prime example of how technological and cultural change is linked with the expansion of a Y-chromosomal lineage, and the contrast of this pattern with that shown by maternally inherited mitochondrial DNA suggests a unique role for males in the transition.
Author Summary
Arguably the most important cultural transition in the history of modern humans was the development of farming, since it heralded the population growth that culminated in our current massive population size. The genetic diversity of modern populations retains the traces of such past events, and can therefore be studied to illuminate the demographic processes involved in past events.
Much debate has focused on the origins of agriculture in Europe some 10,000 years ago, and in particular whether its westerly spread from the Near East was driven by farmers themselves migrating, or by the transmission of ideas and technologies to indigenous hunter-gatherers.
This study examines the diversity of the paternally inherited Y chromosome, focusing on the commonest lineage in Europe. The distribution of this lineage, the diversity within it, and estimates of its age all suggest that it spread with farming from the Near East.
Taken with evidence on the origins of other lineages, this indicates that most European Y chromosomes descend from Near Eastern farmers. In contrast, most maternal lineages descend from hunter-gatherers, suggesting a reproductive advantage for farming males over indigenous hunter-gatherer males during the cultural transition from hunting-gathering to farming.
Discussion
Previous observations of the east–west clinal distribution of the common Western European hgR1b1b2 (or its equivalent) considered it to be part of a Paleolithic substrate into which farmers from the Near East had diffused. Later analyses have also considered variance, and have conformed to the Paleolithic explanation.
Here, we concur that the cline results from demic diffusion, but our evidence supports a different interpretation: that R1b1b2 was carried as a rapidly expanding lineage from the Near East via Anatolia to the western fringe of Europe during the Neolithic.
Such mutations arising at the front of a wave of expansion have a high probability of surviving and being propagated, and can reach high frequencies far from their source. Successive founder effects at the edge of the expansion wave can lead to a reduction in microsatellite diversity, even as the lineage increases in frequency.
The innovations in the Near East also spread along the southern shore of the Mediterranean, reflected in the expansion of hgE1b1b1b (E-M81), which increases in frequency and reduces in diversity from east to west.
In sub-Saharan Africa, hgE1b1a (E-M2) underwent a massive expansion associated with the Bantu expansion.
In India, the spread of agriculture has been associated with the introduction of several Y lineages, and in Japan, lineages within hgO spread with the Yayoi migration, which brought wet rice agriculture to the archipelago.
On a more recent timescale, the expansion of the Han culture in China has been linked to demic diffusion.
In this context, the apparently low contribution of incoming Y chromosomes to the European Neolithic, despite its antiquity and impact, has appeared anomalous. Our interpretation of the history of hgR1b1b2 now makes Europe a prime example of how expansion of a Y-chromosomal lineage tends to accompany technological and cultural change.
Other lineages also show evidence of European Neolithic expansion, hgE1b1b1 (E-M35) and hgJ, in particular. Indeed, hgI is the only major lineage for which a Paleolithic origin is generally accepted, but it comprises only 18% of European Y chromosomes.
The Basques contain only 8%–20% of this lineage, but 75%–87% hgR1b1b2.
Our findings therefore challenge their traditional “Mesolithic relict” status, and in particular, their use as a proxy for a Paleolithic parental population in admixture modelling of European Y-chromosomal prehistory.
Is the predominance of Neolithic-expansion lineages among Y chromosomes reflected in other parts of the genome? Mitochondrial DNA diversity certainly presents a different picture: no east–west cline is discernible, most lineages have a Paleolithic TMRCA, and hgH and hgV show signatures of postglacial expansion from the Iberian peninsula.
Demic diffusion involves both females and males, but the disparity between mtDNA and Y-chromosomal patterns could arise from an increased and transmitted reproductive success for male farmers compared to indigenous hunter-gatherers, without a corresponding difference between females from the two groups.
This would lead to the expansion of incoming Y lineages—as suggested by the high growth rate observed for hgR1b1b2. Similar conclusions have been reached for the Bantu expansion (in which the current Bantu-speaking populations carry many mtDNA lineages originating from hunter-gatherers, the introduction of agriculture to India and the Han expansion.
Some studies have found evidence of east–west clines for autosomal loci.
By contrast, recent genome-wide SNP typing surveys find a basic south–north division or gradient, including greater diversity in the south, but they provide no indication of the time-depth of the underlying events, which could in principle involve contributions from the original colonization, postglacial Paleolithic recolonization, Neolithic expansion, and later contact between Africa and southern Europe.
The distinction between the geographical patterns of variation of the Y chromosome and those of mtDNA suggest sex-specific factors in patterning European diversity, but the rest of the genome has yet to reveal definitive information. Detailed studies of X-chromosomal and autosomal haplotypes promise to further illuminate the roles of males and females in prehistory.
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