The cultural conditions of star-shaped phylogenies

In the generality, I think intergroup selection of paternal lineages is the answer to why star-shaped phylogenies are so evident in the phylogenetic record ~4,000 years ago. More precisely, most of the major clades of R1a, R1b, and I1 undergo massive expansion after a sharp reduction in effective population size around this period. The R lineages diversified during the Pleistocene, probably in Central Eurasia (it is a brother clade to Q). The I lineage derives from Western European hunter-gatherers, probably the late Pleistocene expansion which eventually gave rise to the Mesolithic groups that encountered the early farmers.

But what happened here specifically? Let me quote a section of Peter Turchin’s excellet Ultrasociety: How 10,000 Years of War Made Humans the Greatest Cooperators on Earth:

Lanchester’s Square Law yields an enormous return to social scale. If the opposing forces use a mix of ranged and shock weapons, numerical superiority will still be amplified, although not as much as with purely projectile weapons. So there is an intense selection pressure for cultural groups living in flat terrain to scale up, and a very high price to pay by those that fail to do s….

Though human interaction with horses as domesticates is probably older, light chariots emerged on the Pontic steppe ~4,000 years ago. Within a few centuries, this technology was ubiquitous in the Near East. The Indo-Aryan Mitanni arrive with chariots in modern Syria/Northern Iraq by ~3,750 years ago.

In the Near East chariots and bows were closely associated. The evidence from the Eurasian steppe during the Bronze Age seems less definitive (simply, bows may not preserve very well), though by the Iron Age the mounted archer became a ubiquitous feature of the military landscape.

The combination of chariots, likely bows, and the Sintashta/Srubna/Andronovo culture’s known focus on metallurgy, make it hard for me to deny the likelihood that the expansion of R1a1a-Z93 has something to do with intergroup conflict. The reality is that Lanchester’s Square Law means that even small initial advantageousness for a given paternal lineage will probably snowball. One victory will lead to an increase in territory and resources, which will produce later advantage. A sort of Y chromosomal Matthew Effect.

But this doesn’t explain what occurred in Europe, where R1b and I1 also underwent a massive expansion (and R1a as well). Europe’s relatively forested territory beyond the Hungarian plain always blunted the power and reach of mounted archers later in history. We do know that chariots arrived in the Mediterranean around the same time as in the Near East. But the rise to dominance of the Corded Ware and Bell Beaker peoples predates light chariots. Perhaps it is something as simple as the fact that metaethnic institutions and identities that could dampen intergroup conflict hadn’t emerged, but it’s still curious to me that one could have a ~90% population replacement in Britain in a few centuries.

Perhaps we will find out that it has to do with a disease as our understanding of ancient epidemics gets better.


9 thoughts on “The cultural conditions of star-shaped phylogenies

  1. I wouldn’t dismiss nutritional effects of intensified husbandry, especially cattle herding. The CWC and BBC people had a better health and nutritional status than most of the preceding Europeans.
    They also had genetic advantages which combined well with this, because they were taller and more robust, simply stronger and with a greater reach individually as well.

    Their herds allowed them a mobile, if necessary hit and run warfare, which the farmers and even the hunters in some regions couldn’t afford on the long run. I doubt they needed to fall back to such strategies too often, but they could.
    If you add to those facts a superiour social organisation, with an agnatic patrilinear structure which made the integration of the captured females and mixed offspring easier, together with some technological innovations especially in BB, I just wonder how they couldn’t be successful?
    All of that becomes even more obvious if looking at the state of a lot of those farmer societies before the impact from the East in comparison.

    Its also interesting that the presumably IE CW and BB people were genetically the most mixed people we see in Europe at that time. I think that their genetic variability allowed selection to be even more effective, producing even faster results than in other populations of that time. Taking pigmentation as an example, relevant genes seems to have come from all source groups.
    Most of the farmer communities seem to have been much more inbred in comparison. Actually even signs for negative effects of inbreeding are much more pronounced in some of the farmer groups with very small breeding population sizes. The weak and small breeding populations were most pronounced on the Northern fringes were CWC had its greatest success. Were the farmers had larger and economically more successful settlements, they left more of a legacy.

    The combination of large scale mixture followed by intense selection seems to have been very favourable for the development of those European populations.

  2. With regards to ‘replacement’ and lineage driven socities, Kenneth Nicholls had the following to say in his 1972 book on ‘Gaelic and Gaelicised Ireland in the Middle Ages’

    ($7.73 for kindle version of second edition)

    “One of the most important phenomena in a clan-based society is that of expansion from the top downwards. The seventeenth-century Irish scholar and genealogist Dualtagh Mac Firbisigh remarked that ‘as the sons and families of the rulers multiplied, so their subjects and followers were squeezed out and withered away; and this phenomenon, the expansion of the ruling or dominant stocks at the expense of the remainder, is a normal feature in societies of this type. It has been observed of the modern Basotho of South Africa that ‘there is a constant displacement of commoners by royals [i.e. members of the royal clan] and of collateral royals by the direct descendants of the ruling prince;, and this could have been said without adaptation , of any important Gaelic or Gaelicized lordship of late medieval Ireland.

    In Fermanagh, for example the kingship of the Maguires began only with the accession of Donn Mór in 1282 and the ramification of the family – with the exception of one or two small and territorially unimportant septs – began with the sons of the same man. the spread of his descendants can be seen by the genealogical tract called Geinelaighe Fhearmanach; by 1607 they must have been in the possession of at least three-quarters of the total soil of Fermanagh, having displaced or reduced the clans which had previously held it. The rate which an Irish clan could itself must not be underestimated. Turlough an fhíona O’Donnell, lord of Tirconnell (d. 1423) had eighteen sons (by ten different women) and fifty-nine grandsons in the male line. Mulmora O’Reilly, the lord of East Brefny, who died in 1566, had at least fifty-eight O’Reilly grandsons.
    Philip Maguire, lord of Fermanagh (d. 1395) had twenty sons by eight mothers, and we know of at least fifty grandsons. Oliver Burke of Tirawley (two of whose became Lower Mac William although he himself had never held that position) left at least thirty-eight grandsons in the male line.

    Irish law drew no distinction in matters of inheritance between the legitimate and the illegitimate and permitted the affiliation of children by their mother’s declaration (see Chapter 4), and the general sexual permissiveness of medieval Irish society must have allowed a rate of multiplication approaching that which is permitted by the polygyny practised in, for instance, the clan societies of southern Africa already cited.”

    Given that such practises continued right up to 17th century in Ireland it’s not really surprising we see Star-Shaped Phylogenies in Irish kindred groups. It’s probably also part of reason why some lineages such as R1b-M222 underwent a starburst in western/northwestern Ireland in period after 400AD. (two of quoted individuals above are good candidates for been M222+

  3. Obs:

    “an agnatic patrilinear structure which made the integration of the captured females and mixed offspring easier”

    Why is this so?

  4. @Brian: From what we know so far, PIE was most likely patriarchal, patrilinear, patrilocal, exogamic and agnatic.
    This means all what matters was transmitted from father to son and the culturally transformed kinship was based on the heroic ancestor. This heroic ancestor was key for all relatives of the lineage, regardless of the mother they had. The mothers side had nothing to inherit, nothing to give on, came from another group and the relatives of her were not your relatives in the same sense as those of your father if at all.

    They didn’t even have the ego perspective as the primary focus. In modern Western societies, relatives and kinship starts with you. In the agnatic scheme, it starts with the heroic, even mythical ancestor. The bible has passages going like x was the father of y and y the father of z and so on and so on. That would have been the mantra of any early Indoeuropean you would have met.

    Its always about the ancestry, honour and reputation of your father and your fathers father and so on, whereas the mother might come from far, far away, even from the defeated people of the new colonies. You are still the son of your father and part of the lineage.
    So even two brothers of different mothers, or cousins could still all refer to their real and probably even still living paternal ancestors and finally the great heroic ancestor of the lineage. They would feel no connection to their mothers relatives which would be of equal, if any importance.

    In a modern Western cognatic kinship culture, everything begins with you and you have your fathers and your mothers relatives forming a tree, rather than a line(age). Today even with equal terms in the for fathers and mothers relatives. It is very obvious that your mothers relatives matter too. Even if not as much as your fathers relatives, they matter much more than in an agnatic society, where they were largely ignored and not in your place or group of comrades.
    So kinship and alliances can go through the maternal line too. This makes bands of related male warriors harder to unite and foreign females harder to integrate than in the exclusively patrilinear system on all levels, which PIE seem to have had. You just ignore where the female was coming from. At least once it was accepted by the lineage as a mother of future sons. If that was not the case, for whatever reason, they might have been finished off too. Which seems to have happened often enough.

  5. Are the life expectancies and children per father the same between a cattle herder population and the subdued population? there can be differences in life histories of milk and meat consuming population and that which is lactose-intolerant and consumes less meat. A combination of longer lifetime and more children with polygamy can soon overwhelm the native population. This+diseases can be a factor that cannot be neglected.

  6. “but it’s still curious to me that one could have a ~90% population replacement in Britain in a few centuries.

    Perhaps we will find out that it has to do with a disease as our understanding of ancient epidemics gets better.”

    I still strongly believe that Comanche-style mounted raids and large-scale killing were enough to clear out Northern Europe’s farmers (clearly not the case in the south, however).

    According to Spanish documents, Comanche traders would rape female slaves in broad daylight, lest the Spaniards feel any qualms about buying them due to laws against Indian enslavement. I think a group with that level of dehumanization of outsiders wouldn’t have a problem with depopulating a whole continent of people they considered to be useless or in the way.

    Some fascinating new studies have appeared describing the mindsets of non-state societies that obtain a position of supremacy over other groups. While many small-scale societies can be kind towards outsiders, these groups have a chauvinism untempered by Axial religion or any concept of universal human rights. War, from which their supremacy is derived, is glorified. Santos-Granero’s book, full of hair-raising stuff, speaks of tribes that would conduct yearly raids on groups around them, essentially meaning the weaker societies were slave-breeders.

    Furthermore, I suspect that as an expanding group with this mindset spread out further and its advantages over others increased and its high opinion of itself was constantly upheld by victory, practices became even harsher. For example, it seems the neo-Eskimos (Thule) mixed with locals in western Alaska, but by the time they reached eastern Canada and Greenland, mixture was not on the table. My own Anglo-Saxon ancestors took a long time to get established on the Eastern Seaboard but wiped out the California Indians in a much shorter time: their technological advantages had become greater and their hearts harder.

    The PIEs, with their traditions of wolf-warriors and stories like the Rape of the Sabine Women, fit right into this picture. And so does their partial replacement of central Europeans as opposed to their steamroll in the British Isles. As Greg Cochran has pointed out, any disease-based theory has to grapple with the fact that far more Y chromosomes than mtDNA was replaced in Europe.


  7. I would stress that a lot of what the IE did was not unique. They were just better at it for a variety of reasons.
    Europe saw the overtake of hunter gatherer lineages which seem to have taken control of farmer clans and expanded as more warlike farmer cultures over others. The British Neolithic people had no variety of yDNA as well and their main line seem to have stem from such hunter gatherers. The first farmers too build fortified settlements into hunter gatherer territory. The main difference was that those seem to have stick to their own. Which is logical to me, since they were like European farmers in wildling territory and expanded as whole families. I wouldn’t say they were matriarchal, for sure they were not, but they were probably not as strictly patriarchal and agnatic like PIE.

    The main difference I see between earlier hunter gatherer overtakes is the percentage of hunter gatherer ancestry. PIE represent the most successful of all those hunter gatherer adaptations to the new world of farming and husbandry by a lot. In the West it seems to be about local overtakes of small farming groups and the new mixed ones expanded, with the HG ancestry thinning out rather fast.

    IE on the other hand being predominately HG in ancestry and keeping a fairly high level while aggressively expanding as a group.
    Also, a transition to pastoralism seems to be much more natural for a HG population than crop farming. It really makes a difference for your health and energy intake as well. But I don’t think you can explain any of this without massive violence. Its really about who got the edge over somebody else. And PIE had a lot of edges.
    You know why they won if you look at those who lost. Especially the farmers North of the Alps had a lot of weaknesses. Most of the other people seem to have been largely unprepared for new, incoming enemies with such numbers and advantages.

    Who could stand his ground? People organised the same way or in a very similar way as IE like Semites in particular.
    People living in an environment which was hard to take because of local diseases and climate unfavourable for Northern European like people like a lot of India. The parallels between the later European colonisation of Northern America and the tropical parts of Central and Southern America are very obvious.
    Or people generally so numerous and well trained in warfare that they dould deal with large, well organised tribal armies of healthy and strong men. Those were mostly in the Near East and East Asia, where the most IE could achieve was the kind of overtake we see in Western Europe Neolithics by HG warrior bands in pre IE times. No complete thrust and replacement without local helpers possible.

    And a general question: What would you have done with male capties if you don’t need slaves? There was no organisation or administration to overlook the peasants which territory you have taken? Really they were just your enemies and a future threat to you and your offspring. That again is nothing peculiar IE, but a general pattern. Taking enemy males alive and wishing them good luck after taking their land, resources and wives is simply no option and biologically irrational. You want to secure your life and the well being of your offspring. You don’t want to have unfriendly people in the woods around you don’t need them and can eliminate them.

    What can happen shows the case of Eulau, in which the Schönfelder culture males seem to have killed the whole Corded Ware families in some kind of revenge for whatever. The wives of the Eulau Corded Ware people seem to have come from the Schönfelder too. So they probably made some kind of deal which was broken. Typically the women were not seen as belonging to them, but part of the hostile clan. Once women were married into another clan, they were part of it and no longer of the own family and lineage.

    I don’t know for sure whether any Schönfelder males were tested so far? But they should be mostly part of the Globular Amphora population. Would be interesting to see whether some of the remaining presumably non-IE cultures in Central and Northern Europe had Corded Ware females or not. Because I’m still not sure whether there was a regular exogamic exchange of wives with the people they couldn’t or didn’t wanted to defeat, but which were their neighbours for long periods of time.

    We need a diachronic analysis of all those cultures to see how exactly the takeover took place.

  8. >Some fascinating new studies have appeared describing the mindsets of non-state societies that obtain a position of supremacy over other groups.

    Would you list them?

  9. @Paul

    I think you hit the nail; in strongly agnatic competitive societies, wealthier/stronger male lineages tend to push the others to extinction.

    We see this in the development of European nobility during the Middle Ages, specially outside Germany, and much specially in France, the country where agnatic sucession was strongest. At first, you have noble houses of Frankish, Visigothic, Anglo-saxonic, Suevian, Burgundian, and Gaulish origin; over the centuries, most noble houses in western Europe became Frankish, and most of the Frankish houses became Capetian. The advantages associated with being related to the King of France were great enough to make his male relatives eventually surpass all other noble lineages in number of descendants.

    (Similar thing we see in Japan, where most of the noble clans are either descendents of the royal family or of the closely associated Fujiwara).

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