The Bronze age demographic transformation of Britain

In Norman Davies’ the excellent The Isles: A History, he mentions offhand that unlike the Irish the British to a great extent have forgotten their own mythology. This is one reason that J. R. R. Tolkien created Middle Earth, they gave the Anglo-Saxons the same sort of mythos that the Irish and Norse had.

But to some extent I think we can update our assessments. Science is bringing myth to life. The legendary “Bell Beaker paper” is now available in preprint form, The Beaker Phenomenon And The Genomic Transformation Of Northwest Europe. The methods are not too abstruse if you have read earlier works on this vein (i.e., no Nick Patterson authored methodological supplement that I saw). And the results are straightforward.

And what are those results?

First, the Bell Beaker phenomenon was both cultural and demographic. Cultural in that it began in the Iberian peninsula, and was transmitted to Central Europe, without much gene flow from what they can see. Demographic in that its push west into what is today the Low Countries and France and the British Isles was accompanied by massive gene flow.

In their British samples they conclude that 90% of the ancestry of early Bronze Age populations derive from migrants from Central Europe with some steppe-like ancestry. In over words, in a few hundred years there was a 90% turnover of ancestry. The preponderance of the male European R1b lineage also dates to this period. It went from ~0% to ~75-90% in Britain over a few hundred years.

If most of the genetic-demographic character of modern Britain was established during the Bronze Age*, then there has been significant selection since the Bronze Age. The figure to the left shows ancient (Neolithic/Bronze age) frequencies of selected SNPs, with modern frequencies in the British in dashed read. The top-left SNP is for HERC2-OCA2, the region related to brown vs. blue eye color, and also associated with some more general depigmentation. The top-right SNP is in SLC45A2, the second largest effect skin color locus in Europeans. The bottom SNP is for a mutation on LCT, which allows for the digestion of milk sugar as adults.

The vast majority of the allele frequency change in Britons for digestion of milk sugar post-dates the demographic turnover. In other words, the modern allele frequency is a function of post-Bronze Age selection. This is not surprising, as it supports the result in Eight thousand years of natural selection.

1000 Genomes derived SLC45A2 SNP frequency

At least as interesting are the pigmentation loci. The fact that the derived frequency in HERC2-OCA2 is lower in both British and Central European Beaker people samples indicates that the lower proportion is not an artifact of sampling. Britons have gotten more blue-eyed over the last 4,000 years. Second, SLC45A2 is at shocking low proportions for modern European populations.

HGDP derived SLC45A2 SNP frequency

In the 1000 Genomes the 4% ancestral allele frequency is almost certainly a function of the Siberian (non-European) ancestry. In modern Iberians the ancestral frequency is 18% (and it is even higher in Sardinians last I checked), but in Tuscans it is ~2%. Though not diagnostic of Europeans in the way the derived SNP at SLC24A2 is, SLC452 derived variants are much more constrained to Europe. Individuals who are homozygote ancestral for SNPs atSLC45A2 rare in modern Northern Europeans (pretty much nonexistent actually). But even as late as the Bronze Age they would have been present at low but appreciable frequencies.

This particular result convinces me that the method in Field et al. which detected lots of recent (last 2,000 years) selection on pigmentation in British populations is not just a statistical artifact. Though these papers are solving much of European prehistory, they are also going to be essential windows into the trajectory of natural selection in human populations over the last 5,000 years.

* In the context of this paper the Anglo-Saxon migrations tackled by the PoBI paper are minor affairs because the two populations were already genetically rather close. Additionally, the PoBI paper found that the German migrations were significant demographic events, but most of the ancestry across Britain does date to the previous period.

47 thoughts on “The Bronze age demographic transformation of Britain

  1. I have no idea why Tolkien felt the need to create an English mythology. Anglo-Saxon mythology proper doesn’t seem to have been all that different from the Norse. Our days of the week are named after Nordic gods. Earlier Briton mythology wouldn’t have been that different from the Celtic stuff we have.

    On a broader note, it is interesting that we really have only three traditional pagan mythologies from Europe: Celtic, Nordic and Classical. The Slavic myths seem to have truly died out.

  2. Is the strength of selection among Europeans in the last few millennia surprising to scientists working on the topic, or not? We all know Gregory Cochran expected it, but how widespread were his ideas?

  3. it’s surprising to most people i talk to. the people who worked on part of the SDS paper didn’t even push back much when i wondered out loud if it was an artifact.

    1. For something like eye colour it’s not obvious to me how that could be under strong selection imposed by the environment – but sexual selection, perhaps associated with cultural norms, I can see how that could act very quickly.

      1. i don’t think it was selection for eye color. the locus has lots of other genetic effects. eye color came be a side effect.

        but sexual selection, perhaps associated with cultural norms, I can see how that could act very quickly.

        how? you can assert it verbally but have you thought about this in any detail?

        sexual selection seems to be a lazy catchall fallback. scientists indulge in this too. the reality is we just don’t know.

      2. Dark eye color could happen as a result of natural selection in low latitudes, as my understanding is people with dark irises actually do have less issues with sun glare on the whole. This could make a big difference for a hunter-gather (or a warrior) in very sunny areas, but one would expect where it’s dim and overcast, or where sun glare isn’t a matter of life or death (like the average farmer) selection would be relaxed.

        But no, it’s hard to think of any sort of fitness advantage having light eyes proffers. As Razib said, it’s likely a side effect of another trait being selected for.

        1. One bit example of pleiotropy is in domesticated foxes with tails, patches of fur being different, etc.

          If I had to Guess, blue eye Color in cold weather didn’t hAve the negative selection it had in tropics, and had some positive pleiotropic correlation we will discover some day either immunological , neurological, who knows.

  4. Some areas within Europe have been more selective for SLC45A2 than others, Tuscany and Britain apparently belong to the former. Ancestral rs16891982 in French sample (n>1200) of Walsh et al. 2011 was 14,5%. Their Italians had the ancestral allele (6%) more commonly than HGDP/1kgenomes Tuscans, like HGDP Bergamo does. British consistently show <3% frequencies, continental Europe does not.

    All in all the distribution seems to not form clean clines that can be linked to regional ancestries, given that Italy – or some major Italian regions at least – and Britain demonstrate higher frequencies than many "in between" and there are other examples.

    https://alfred.med.yale.edu/alfred/SiteTable1A_working.asp?siteuid=SI003963V

  5. Does this mean that the pre-Beaker British originated from Iberia?

    “A new finding that emerges from our analysis is that Neolithic individuals from southern France and Britain also show a greater affinity to Iberian Early Neolithic farmers than to central European Early Neolithic farmers (Fig. 2b), similar to previous results obtained in a Neolithic farmer genome from Ireland.”

    In trying to imagine what a 90% turnover means, I assume that visible physical differences help, along with a very strong martial culture supported by religion, heroic tales, status recognized by grave goods, and the quest for copper.

    1. more precisely, they travelled along the atlantic fringe. this is not a new idea.

      In trying to imagine what a 90% turnover means, I assume that visible physical differences help, along with a very strong martial culture supported by religion, heroic tales, status recognized by grave goods, and the quest for copper.

      i wonder if disease played a role. we have precedents in our world.

      1. The idea of an epidemic similar to the Colombian exchange is attractive. The issue I have with it is why would it result in total population collapse in Britain, but not much of anything in Iberia? The two populations were broadly similar, meaning we should presume their immune system response to a new zoonosis would be pretty analogous. Perhaps cross-regional population contact was still sporadic enough that a deadly disease could be confined to Britain without spreading elsewhere?

      2. Thanks. I’ve read a few of Cunliffe’s books and noticed he was consulted here. I’ve just skimmed his writing on the Beaker period in “Britain Begins,” and it seems like he took an accommodationist stance btw/ movement of people (from the Eastern channel) and transfer of ideas. Probably too accommodating.

        I wonder if the population of Britain was not as extensive as we may have previously thought, or if there is something about the native people that should be considered: was the culture that built the henges and monuments particularly vulnerable to the invasion?

    2. I think 90% turnover means that Britain had pretty much reverted to hunting and gathering with domesticated animals pretty much limited to sheep, goats and maybe pigs. This caused population collapse. The horticulture they had used in the first wave Neolithic failed for some reason (probably some combination of bad climate and exhausted soils that weren’t rotated).

      Bell Beaker folk, in contrast, know how to have a cattle based, much more productive pastoralism supplemented by hardy domesticated plants, and tuned their culture to thrive in arid conditions with poor soils on the steppe. They thrive and ten times as many of them can live in comfort as the residual British hunters and gatherers whom they more or less exclude from their society and ignore at least for the first several centuries. As the shine comes off their methods and the locals start to imitate and adapt, “indigenous” Britons are integrated into their society causing R1b percentages to fall a bit.

      By comparison, when the Neolithic revolution hit Egypt for the first time, its population increased by 100x from the pre-Neolithic population.

      The Bell Beakers surely did kill some of the locals, but this was colonization not a war band of single men, and they could just swamp the locals demographically with their superior food production capacity.

      1. I wonder if there was some sort of systematic crop failure similar to the Irish potato famine during this period? The little bit I know about Neolithic Europe’s crop package suggests that it was steadily dropping Near Eastern crops as time went on. If the EEF’s crop package was reduced to relying on one cereal crop in Britain during the crucial time period. Hell, certain plant pathogens (like smut) can be transmitted by cattle through their intestinal track, so if the Bell Beakers had cows which were carriers they could cause crop failure basically anywhere they allowed their herds to graze.

        1. That’s interesting. Analysis of skeletal remains of an early Chieftan (pre-Bell Beaker) buried near Stonehenge concludes that his diet was almost entirely meat. They also concluded that he migrated from south Wales to Stonehenge as a boy and probably traveled frequently between the two areas as an adult.

  6. Well Thursday, we really do not have any surviving Celtic mythology. That seems to have died in the early centuries A.D. while the Celts were under Roman dominion. What people really mean when they say ‘Celtic’ are the mythologies of the Gaeil and Brythoniad, who were never identified as Celts – untill the English started calling them that in the 18th century!

    Razib, I should be very slow using the political term ‘the British Isles’ – its a political nickname for the first UK of 1801-1919 (“The United Kingdom of Great Britain and Ireland” – no wonder it needed a nickname!). Because it does confuse what are “their British samples”? Norman Davis’s book is far from excellent on non-Anglo matters but even he notes that the phrase cannot be used before or after certain dates (which he nevertheless gets wrong).

    “male European R1b lineage also dates to this period. It went from ~0% to ~75-90% in Britain over a few hundred years.” Possible, though that seems far too small a time-scale. How do we know? Could it be this is back-projecting later demographics? And where – Britain, Ireland, or both?

    Thanks for this!

    1. “male European R1b lineage also dates to this period. It went from ~0% to ~75-90% in Britain over a few hundred years.” Possible, though that seems far too small a time-scale. How do we know? Could it be this is back-projecting later demographics? And where – Britain, Ireland, or both?

      what the fuck are you talking about? i’m alluding samples in the paper. they’re dated. ?

    2. Norman Davis’s book is far from excellent on non-Anglo matters but even he notes that the phrase cannot be used before or after certain dates (which he nevertheless gets wrong).

      why don’t you speak more than ex cathedra? i have no idea what you are talking about. davies is ethnically welsh and he makes a special note early on that he will pay more than the usual attention to the ‘celtic fringe’ in his work.

    3. British Isles were named by the Greek explorer who discovered them. Admittedly as the Pretannic Isles. The Romans made it Britannia. Irish nationalist crazies object to the term. Great Britain goes back to James I succeeding Elizabeth and uniting England and Scotland. The UK was as you say 1801.

      1. Razib, I’ll reply to your points when you apologise/cool down, or not at all. No need for insults to straight questions.

        [content deleted; that’s for giving me lip]

        1. Razib, I’ll reply to your points when you apologise/cool down, or not at all. No need for insults to straight questions.

          oh bro, you don’t fucking understand. here i don’t apologize to you. if you say something i think is confusing or stupid you explain yourself. no discussion. that is all.

    4. Adrian,

      As Razib points out we know that it happened based on the dataset included in the paper, they have both Neolithic and Beaker period samples which come from a dated context (C-14 etc.) R1b is completely absent in Neolithic samples which follows the pattern that we have seen in other parts of Europe. The Beaker R1b is nearly all also R1b-P312. (which has a TMRCA of 4400-4900 years before present — based on NGS tests)

      For example:
      “We detect 10 males who belonged to R1b-L21/M529, all of them dated to the Beaker and Bronze Age periods and excavated in Britain. This matches the high frequency of this clade in modern populations from the British Isles.”

      Obviously we also have an additional 4 L21+ men from Rathlin Island as published last year. As we know from likes of Busby (Royal Society) R1b-L21 probably peaks at ~70% in Ireland in the present day.

      Leaving aside Y-DNA it’s obvious that the R1b individuals that were tested as part of this paper show population discontinuity from the previous Neolithic population (Steppe component etc.)

      I’d recommend that you read the paper (and the supplementary information) see:
      http://biorxiv.org/content/biorxiv/early/2017/05/09/135962.full.pdf

      http://biorxiv.org/content/biorxiv/suppl/2017/05/09/135962.DC1/135962-1.pdf

      As we saw in the paper last year the Neolithic Irish sample fits the pattern of Neolithic remains from across western Europe and is quite distinct from modern Irish population.

  7. One more thought – looking at British Isles Y-DNA, the modern non-R haplogroups are almost entirely I1. While Neolithic Britain seems to have been almost entirely I, it was I2 – mostly found in the Balkans and Sardinia today (basically areas where lots of “old European” ancestry survived). Modern British I1 probably dates from modern history – the Norse and Anglo-Saxon migrations.

    1. Maybe, but I1 is most common in Britain along the North Sea – basically in the areas where the Anglo-Saxons settled in large numbers and the Danelaw was later formed. It’s lowest in “celtic fringe” areas like the Highlands of Scotland, Wales, Cornwall, and eastern Ireland. To me that seems to suggest the most common branch of R1b in the British Isles is the “celtic” haplogroup (though the Anglo-Saxons may have introduced others as well).

  8. Odd orthography in Ros’s surname on the west Iberian paper. Ó Maoldúin or O’Maolduin (or, with a wince, O’Maoldúin) work, but not both a fada and an apostrophe as in Ó’Maoldúin).

  9. Aren’t infectious diseases the great selective pressures of civilization. The Plagues of Justinian and all that. Did the Germanics have resistance that the Romano-whatevers did not? That would have changed ratios in the population even if the Germanics had been around a while. The Belgae may have been Germanic. The Romans interrupted their migration into Britain. Belgium is rather close to The Netherlands. Half of them are Flemish.

    1. I think it’s a mistake to presume that the Germanic peoples were ever a coherent ethnic group. Modern genetic studies have shown that in Germany alone some German-speakers are very heavily shifted towards Slavs, while others are shifted towards the French. The point being that even if the Belgae were German-speakers, they may have been a Germanized population of largely Celtic ancestry.

      1. Was that true though Modern Era? The Germanic spectrum I mean from Slavic leaning to French leaning. Or is that a result of last five hundred years?

        I’d Guess (I have no idea though) that say Germanic mega tribes of Peter Heather type that ravaged Roman Empire were probably genetically pretty close with little in the way of the big genetic spectrum you’re discussing of modern Germany.

        I’d be curious of papers discussing this topic, cuz I really don’t know.

      2. Karl, I think you’re probably correct (and would give majority odds to what you would expect), but:

        Differentiation between Northern Europeans tends to look pretty low when placed into these pan-West Eurasian analyses, or European analyses with Sardinians and Basques. E.g. – http://www.nature.com/nature/journal/v513/n7518/images/nature13673-f2.jpg / http://imgur.com/6F9849I. Not much differentiation between NW-NE Europe compared to SW-SE.

        Run with a restricted set of European populations, though – https://liorpachter.files.wordpress.com/2014/05/pca_lao.jpg (“run against 2541 individuals x 309,790 SNPs”) – and differentiation NW-NE (Ireland-Poland) is actually quite as profound as SW-SE (Spain to Greece).

        (Other examples: Novembre 2016, Figure 1 – http://www.sciencedirect.com/science/article/pii/S0959437X16301113, Heath 2008 – http://www.nature.com/ejhg/journal/v16/n12/full/ejhg2008210a.html, or 23andme, with *very* large n https://www.23andme.com/ancestry-composition-guide/).

        Why the contrast? My guess is present day North European differentiation is from differences largely orthogonal to the patterns coming from descent from the various European HG->Neolithic farmers.

        One way this could be true is if genetic isolation, founder effects and drift between populations on the North European plain were moderately strong for an unspecified time following the initial Bronze Age expansions. (And Indo-European languages were also differentiating with a fairly high time depth; these people were not part of a single speech community). Which is my roundabout way of saying we may possibly end up finding a genetically isolated ancient “Germanic” population to a greater degree than we might initially think, once more Iron Age samples are in.

  10. A 90% turnover, wow. That’s got to be a combination of disease and significantly higher birth rates among the replacements – you just don’t get that kind of turnover without mass death that’s difficult even with warfare.

    1. One thing to think about is just numbers. If a new innovation can support 10x as many people, and it isn’t easy to replicate, then those people can soon become 90% of the population without killing anyone at all.

      Simple things like having metal axes for cutting down trees in wet areas that don’t burn well could even give a huge immediate advantage.

      1. I was wondering when you were going to show up and comment on these papers! Waiting for a post on your blog…

  11. What is most surprising to me is that the scale of the R1b/steppe/Beaker population explosion in western Europe was on a similar scale and speed as the R1a/steppe/CordedWare population explosion in eastern Europe, yet there was so little overlap in Y-haplogroup territory.

    I understand how this situation can easily remain after the initial settlement of a large population, but how did they stay so distinct during these major migration periods? Why didn’t Corded Ware people hear about this big boom on the islands and jump in?

  12. Please explain to a general reader what this indicates in historical terms. Does this mean celtic britain being resettled by Anglo-Saxons?. Or something older like Yamnaya people mixing with neolithic Otzis #Duh

    [the second -Razib]

  13. Please explain to a general reader what this indicates in historical terms. Does this mean celtic britain being resettled by Anglo-Saxons?. Or something older like Yamnaya people mixing with neolithic Otzis #Duh

    [what’s up the double comment? did you mean to do this? did you get a 503 -Razib]

  14. “Did the Germanics have resistance that the Romano- whatever did not?” It seems the territory that was to become Mercia was decimated at this time. The survivors took off to Armorica (Brittony in France) taking their placenames with them. The Britons at this time were still in contact with the old Mediterranean and Black Sea trade, and took great pains to keep away from the newcomers. Some years later the Anglo Saxons just walked into the empty area totally unresisted until they reached Cirencester … This ‘Roman’ attitude towards their former auxilliaries may – at least partly – explain the near-total absence of Brythonic loanwords in English.

    1. The Britons at this time were still in contact with the old Mediterranean and Black Sea trade, and took great pains to keep away from the newcomers.

      the elites. this is what i think is key (even in saxon areas there are plenty of genetic signatures of non-germans, and there are clear allusions to britons in the legislation of the early saxon period).

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