Seven years ago I wrote 1 in 200 men direct descendants of Genghis Khan. It’s the most popular post I’ve ever written. As of now there have been 630,000 “sesssions” (basically visits) on that page alone. I suspect that many more have read my summary of The Genetic Legacy of the Mongols, the original paper on which it was based, than that paper (though it’s a good paper, you should read it).
At the time I wrote that people often asked me if I was a descendent of Genghis Khan. That seems unlikely on the paternal lineage. My Y chromosome is R1a1ab2-Z93. This is typically found in South Asia, and among Iranian peoples, as well as in the Altai region of western Mongolia. It is not common among Mongols though, even if it is found amongst them, likely due to gene flow from the west. The particular branch of R1a1a that I carry has been found in ancient remains from the Srubna culture of the eastern Pontic steppe. As a friend of mine might say, I am the scion of marauders from the steppe, even though not Genghiside ones. The fact that I have the last name Khan is simply a legacy of the custom whereby South Asian Muslim lineages of a particular status accrued the surname to denote their position within Islamicate civilization.
But though I am no direct descendent of Genghis, it turns out that my Y chromosome shares a similar history. The figure to the left is focused on European Y chromosomes, and at the top you see various “R” lineages. It turns out that R1b and R1a are both basically subject to the same explosive dynamics as the Genghis Khan haplotype: both exploded into star phylogenies relatively recently in time. Trees of the R1 lineages always show them to exhibit a rake-like pattern. This is due to the fact that starting from a small base they expanded so rapidly that they did not develop the intricate node-structure you see in lineages which accrued mutations at a more normal pace.
What could have caused such explosive growth? We know why Genghis Khan and his sons left so many descendents: conquest yielded social status. For many generations having a male Genghiside bloodline was highly effective as a means to gain bonus points when attempting to scale the summits of power and wealth. This was even true in the Muslim regions of Central Asia, despite Genghis Khan’s negative impact on Islamic civilization (Transoxiana arguably never recovered from this period).
We don’t have anything like the “Secret History of the Indo-Aryans” to explain the emergence of these older star phylogenies. In The Horse, the Wheel, and Language, David Anthony argues that mobile populations domesticated the horse, and used that as a killer cultural advantage to spread their Indo-European language. In his book from the 2000s Anthony argues for elite transmission of language by the Kurgan people. But more recently he has been persuaded by genetic work which suggests massive population displacements and migrations into Europe during the late Neolithic and early Bronze Age.
Unfortunately the timing doesn’t work from what I can tell. The expansion of groups like the Corded Ware seem to pre-date the emergence of the steppe chariot toolkit by many centuries. It does so happen that the chariot was invented in the region where R1a1a2b-Z93 was also found to exist. So I suspect this “Scythian” R1a lineage did sweep across much of Central-South Eurasia thanks to the horse and the wheel. But a technological explanation is more difficult for the rest.
I will posit another speculative answer, stealing the idea from Snorri Sturluson. He believed that the gods that were remembered by his pagan Norse ancestors were at one point men of great renown and fame. Kings of yore. Over time they had been deified, and legends had grown up around them. Sturluson may have been right. Perhaps the Indo-European gods recollect the forefathres of R1a and R1b. What was there advantage? Perhaps it was a hierarchical stratified social structure which brooked no individualism against the interests of the lineage unit? It may be that asabiyya is worth more than a chariot?
Culture isn’t fitness neutral, but the selective fitness of a culture is context dependent. The expansion of R1a and R1b coincides with major arid climate events that extended from Europe to India. These climate events disrupted civilizations that had adapted themselves to favorable conditions that had ceased to exist, and favored cultures adapted to more harsh conditions which were now widespread. When the regimes based upon the old cultures collapsed, the peoples who were better adapted to harder times rushed into the vacuum. The dialectic between the civilized peoples and barbarians extended deep into prehistory and continued well into recorded history.
It might not even be over. If climate change or some other factor leads to the decline of the “civilized” parts of the world, the “barbarian” cultures (mostly conservative and religious) may rush in once again if they are better adapted to surviving in hard times.
RE: Snorri Sturluson: Omeljan Pritsak goes into this {The Origin of Rus’, Vol 1: Old Scandinavian Sources Other than the Sagas}. Always an interesting writer, if sometimes a fabulist over an historian, Pritsak posits Odin as “Tykja-konungr” or Turk-Khagan. While the dating may be chronologically misplaced the theme relates to leaders who were great warriors from the East. Frankish myths contain a similar ethos.
It seems to me that “civilized” parts of the world tend to be located in colder climates which could benefit from global warming (although, being less agrarian, to a limited extent), although a collapse in equatorial regions could send people rushing out.
Razib — was it on this blog that you recommended “When They Severed Earth From Sky”?
https://www.amazon.ca/When-They-Severed-Earth-Sky/dp/0691099863/
If not, I recommend it. The authors bring up the concept of conflation (e.g. legends about people with similar names get conflated into a narrative story about a single “hero” or “god”)
As an aside, can you tell me how to drill down to the subtype of my YDNA haplogroup? Like you, I am R1a1a (23andme has now updated it to R-M512) but doesn’t give me any additional information. Neither GEDmatch nor DNA.land look at Y-DNA at all. My most remote patrilineal ancestor I am aware of was a German born in Berlin sometime in the mid 19th century. I am guessing it is fairly likely that like many in the east of Germany he came from a Germaized Slavic background originally, but I know some R1a1a lines are common even among Germans.
Although it doesn’t seem like the primary cause in the case of Indo-European, I have always wondered about the degree to which language shift can be accelerated by providing a common social/economic framework across a wide geographic area. Consider as an example Tok Pisin in New Guinea, or various European languages in Africa. When a hegemonic power moves into an area which is formerly divided among numerous languages, those who speak the “imperial” language will tend to accumulate economic advantage, because they have a greater ability to migrate more widely to find economic opportunity and take advantage of developing regional trade networks. As a result languages which were formerly only spoken by the conquered as a second language can transform into a first language for their children. In the longer run, those speakers of the new languages should have the potential of greater fitness, because the potential upside (at least, if you’re male) of being part of a wider regional network is so much greater. In the case of PIE, this could have meant hearing “through the grapevine” of economic opportunity (read, rape and plunder) hundreds of miles from your place of birth, along with the ability to travel those long distances and take advantage of that knowledge.
“The fact that I have the last name Khan is simply a legacy of the custom whereby South Asian Muslim lineages of a particular status accrued the surname to denote their position within Islamicate civilization.”
OTOH, Kahns, such as my maternal maternal great grandfather, are genetically connected. They are members of the caste of priests of the Jewish People. The Hebrew word for priest is transliterated variously as Cohen, Kahn, and Kagan.
I thought the model for PIE expansion was more about ox-carts, horse-riding, and cultural habits allowing for long-distance contacts (hospitality) and confederacy-building (comitatus).
Chariots would have been part of a later (maybe Indo-Iranian, maybe satem generally) expansion that had moved the mobility, and maybe the caste specialization, up another notch.
predates horse-riding. as for hospitality, they had to kill all their neighbors first. the genetic evidence is strong.
I thought the Botai bits pushed back the horse-riding timeline. Hospitality: indeed, and having a hospitality tradition among your fellow tribals makes it easier to organize a bigger horde.