La France: blessed eldest daughter of a blessed continent

Why the French always seem to regain the upper hand, a geographic and genetic exploration, Part 2 of 2

Note: part 2 of 2, previous post

As the pyramids were rising on the Giza plateau in Egypt between 2600 and 2500 BC, the Neolithic societies that had dominated France for 2,500 years were coming apart at the seams. Environmental catastrophes set the stage, both the shocks of climate change, inducing a shift toward lower-intensity farming and pastoralism, and plagues that triggered social collapse. Neolithic Europe was already in a weakened state in 3000 BC, when Eurasia’s first nomads, the Yamnaya of the Pontic steppe, began to settle across the continent’s north and east. But for a time, Neolithic Europe continued on, less buffeted by change in the Mediterranean peninsulas of the south, in Britain, and in what was to become France. Then, around 2600 BC, the centuries-long frontier between Neolithic and Indo-European people in the Rhine valley could no longer hold; agro-pastoralists with copper weapons and bell-shaped beakers were now streaming across the ancient boundary, forcing their way into and absorbing the native societies.  

One of the most telling aspects of the shift to a new dispensation is that the paternal lineages, the Y-chromosomal haplogroups, change abruptly across the Neolithic-Beaker transition. The figure above illustrates it starkly. The Y lineages in the Seine-Oise-Marne culture, northern France’s final Neolithic society in the third millennium BC, were predominantly I2, G and E. The Beaker culture, which replaced the Seine-Oise-Marne piece by piece in the middle centuries of the third millennium, was overwhelmingly R1b, still the dominant lineage of France today. From what we know of proto-Indo-European society, it was patriarchal. The culture ancestral to the Bell Beakers in western Germany, the Single Grave, were clearly organized around kinship groups of related males. The replacement of one group of paternal lineages for another indicates a power shift. The Single Grave populations in western Germany, descended from steppe pastoralists, but had accrued substantial Neolithic farmer admixture along the way and were associated with burial goods like axes and daggers. Evidence of conflict in the region between Neolithic populations and intrusive pastoralists is plain in the archaeological record.

Neolithic site at La Roche

Of Beakers and Blades

But not all interactions may have been so violent. A new paper sampling seven individuals dating to ~2500 BC buried near Troyes southeast of Paris hints at possible peaceful integration of steppe males into Neolithic societies; genetically the population is overwhelmingly descended from Anatolian farmers, but a father-son pair among the samples are 50% and 25% steppe respectively. This means that at some point in an earlier generation a Bell Beaker male integrated into the otherwise apparently Neolithic community, the son’s grandfather and the father’s father. The implication here is that a Neolithic culture in the region was changing genetically via the assimilation of males migrating out of the northeast. 

A broader survey of samples from late Neolithic and early Copper Age France shows a pattern worth pausing to consider: individuals’ X chromosomes recurrently skew to predominantly either steppe, or (more often) Neolithic ancestry compared to the genome as a whole, which usually remains more balanced regardless of which ancestral component the X’s favor. So for example, an individual’s overall genome might be 55% steppe, while the steppe-derived segments on the X chromosome total only some 20%). Since females carry two X chromosomes and males just one, about 66% of the time the X is being passed through a female of the population, making its genomic history a window onto sex dynamics. This skewed pattern accords with a mating bias where steppe admixture into the native populations occurred primarily via males, who only contribute a single X chromosome to their daughters, and none to their sons (so they’re pitching in 50% steppe across the non-sex genome, but only 33% on the X chromosome). The culture of steppe-derived peoples seems to have remained patrilineally exogamous, so men of steppe-enriched background routinely paired up with Neolithic women, but women of dominant steppe heritage rarely paired up with men of Neolithic background. This bifurcated dynamic of matings kept the X-chromosomal pools more segregated in the initial centuries of Indo-Europeanization in France. Eventually, recombination between two X chromosomes in women of mixed background diminished this skew, but not for centuries after the initial admixture. 

Though pockets of mainland Western Europe remained where individuals with nearly unmixed Neolithic ancestry persisted as late as 1000 BC (and Mediterranean islands like Sardinia remained much more insulated from Indo-European populations’ migration until even far later), by about 1900 BC, almost all samples out of regions like Iberia and France are a mix of steppe and Anatolian farmer. The replacement of earlier Y-chromosomal lineages, the end of megalith-building and emergence of daggers and bows among grave goods, plus the proliferation of new ceramic styles like bell beakers across much of Europe in the centuries after 2600 BC all point to a main period of admixture between local Neolithic populations and intrusive Indo-European speakers. Genetic analysis of earlier Corded Ware populations in Eastern Europe and Scandinavia suggests that after an initial admixture with the Neolithic Globular Amphora culture (GAC) in Poland, minimal absorption of Central Europe or Scandinavian farmers occurred. In the Rhine basin though it seems a new group of post-Corded Ware pastoralists integrated with local farmers, as their Yamnaya-ancestry proportion drops from 70 to 60%, and a new Y-chromosome lineage, R1b, rises to the fore.

As Bell Beaker people pushed into France, Iberia and Italy, the process of admixture began anew, and the genomes indicate a strong pulse of Neolithic ancestry in steppe-derived individuals dating to ~2500 BC. All Western European populations are to some extent a mix of these two ancestral groups; more steppe in the north, more Neolithic in the south. But culturally the overwhelming majority derive from proto-Indo-European societies with prehistoric roots on the steppe. The replacement of Celtic languages across Western Europe was a blow to cultural diversity, but linguistically, one Indo-European language family just overturned another (Romance and Germanic for Celtic). Indeed, many scholars believe that the Celtic languages themselves spread with the expansion of the Urnfield archaeological culture after 1000 BC, thus absorbing yet earlier Indo-European societies descended from the Bell Beakers.

There is of course one exception to this trend: the Basques, who occupy both sides of the Pyrenees in northern Spain and southwest France. Their language is plainly not Indo-European, and genetic peculiarities like their high frequency of Rh-negative have long suggested they may be a relict population of an earlier European epoch. On the whole this is not unwarranted. A 2019 study confirms that the Basques have been genetically isolated since the time of the Roman Empire. But previously, they must have interacted extensively with Indo-Europeans, because over 80% of Basque men carry the R1b paternal lineage, which clearly arrives via the Bell Beakers. In fact, most Basque men carry a mutation on R1b that seems to have sprung up in France 4,500 years ago, spreading southward into Iberia after 2400 BC. 

What explains this pattern? Strabo and other ancient writers have alluded to a high status for Basque women, with the possibility of matrilineal inheritance (a custom that in northern Spain may have spread to Muslims as well). The genetic evidence from the new paper with samples from Troyes suggests that integration of men with steppe heritage occurred 4,500 years ago in Neolithic communities; it is not implausible that if the ancestors of the Basques were matrilineal that could have enabled Neolithic cultural continuity, sidestepping replacement by Indo-European language and religion to match their new Y-chromosomes.