A new paper in The American Journal of Human Genetics, The Kalash Genetic Isolate: Ancient Divergence, Drift, and Selection, illuminates and obscures the history of this enigmatic people. Some framing is necessary here for why the Kalash are important. The Kalash are a “pagan” people who live in the uplands of Pakistan. By pagan, I mean to say that they preserve the primal religious traditions of a strand of the Indo-Iranian peoples, untouched by Islam, or, later developments which led to “higher religions” which arose directly out of Indo-European religion, Zoroastrianism and Hinduism (Sanatana Dharma). It would perhaps be defensible to depict the Kalash as the pagans of yore, a fierce people unbowed by philosophical monotheism or the quietism which explodes out of aspects of the gita.
Which brings us to another peculiarity of the Kalash: they are white. By white I do not mean white Europeans. They are not. The genetics is not in dispute, the Kalash are distantly related to the other peoples of South Asia. Some South Asians remind white Europeans (and also white West Asians) of themselves when they look at them face to face. But this tendency is heightened in isolated mountain peoples, such as the people of the Chitral valley. Among the Kalash it is more the norm the exception, ergo, legends of descent from the armies of Alexander the Great. In a previous age this paradox of an exotic and pagan barbarian people whose external appearance was white was utilized in fiction. Rudyard Kipling’s novel The Man Who Would Be King is set among the people of “Kafiristan,” what is today called Nuristan. Eight years after the publication of Kipling’s book the people of this region were forcibly converted to Islam by the king of Afghanistan. Even today if a Westerner wants to “pass” as an Afghan it is mostly plausibly as a Nuristani, because some among these people look to be Western in their outward appearance. The Kalash people were under British rule, and so were shielded from conversion to the religion of peace. Today the Kalash are surrounded by territories infested with Pakistani Taliban. Though protected by the state of Pakistan and vigilant against interlopers, it still seems unlikely that they’ll pass through the next generation unconverted.
The Kalash Genetic Isolate is open access, so I invite you to read it. I saw part of the above figure at ASHG 2014. The important aspect of this paper is that it confirms that the Kalash have a great deal of “shared drift” with MA-1, the canonical individual which represents the ancient North Eurasian people who contribute ~10-20% of the ancestry of Northern Europeans and 30-40% of that of Native Americans (and nearly as much as some Caucasian peoples). Unfortunately the tables don’t show f3 statistics of each population, so we aren’t totally clear which population is which in the ternary graphs. But we can make some guesses. The outlier South Asian group is almost certainly the Sino-Tibetan Sherpa group. The South Asian groups include the Gujarati sample from the 1000 Genomes, as well as HGDP populations such as the Sindhis. The West Asians are Iranians, Palestinians, Turks. etc. if this is correct it seems to depict South Asians as sharing a great deal of drift with MA-1. There is also a second plot which shows that Kalash share a great deal of drift with La Brana, the Mesolithic hunter-gatherer from Spain. In contrast to the result from MA-1 it does not seem that other South Asian groups share this drift. To me this is tentative support for the contention in last year’s Science paper that there was some gene flow from Europe to the Kalash over the past few thousand years.
But I need to end here on a down note. Though a lot of the results in this paper are fine, the interpretation strikes me as totally out of kilter with their own citations! They say:
LD decay showed that the Kalash were the first population to split from the other Central and South Asian cluster around 11,800 (95% CI = 10,600−12,600) years ago. This estimate remained constant even after the addition of an African (YRI) population or when the Kalash were compared with different subsets of non-African populations. The pairwise times of divergence with other Pakistani populations ranged from 8,800 years ago with the Burusho to 12,200 years ago with the Hazara.
Most of the populations and clusters that they are speaking of here did not exist when the divergence has been adduced. The Hazara for example are a compound population which emerged in the last 1,000 years due to the admixture of Mongols upon a Persianate substrate. The Uygurs are similar. The “Central” and “South Asian” population genetic clusters are refications of admixed groups which have emerged in the past ~4,000 years. That is, thousands of years after they purportedly diverged from the Kalash. The problem here is that the authors keep forcing their interpretations into a tree, when population genetic history for humans in the Holocene has not been a tree at all. As outlined in Towards a new history and geography of human genes informed by ancient DNA it is plausible that every major group of humans today (major = numerous) is the product of fusions of branches of the human race which were sharply diverged during the Pleistocene. The genomes of individuals and peoples then represent a complex and reticulated graph of interlaced histories. Reducing them to branching trees obscures rather than illuminates.
The deep divergences being inferred here strike me as likely a function of the fact that the authors do not take into account that South Asian populations are themselves a compound of two very distinct groups. One of these, the “Ancestral South Indians” (ASI) are very diverged from the groups of western Eurasia (and, the “Ancestral North Indians”, the ANI). The peoples to the south and east of the Kalash have much higher fractions of ASI, so the calculation of a divergence that is >10,000 years before the present is simply reflecting the very deep divergence of the ASI ancestry from the West Eurasian heritage of the Kalash (note, it is important to remember that the Kalash also have ASI, but just at lower levels).
Overall, this is an interesting paper. There are notable nuggets in it. For example, phenotypically the Kalash are lactose tolerant, but they lack the common Eurasian variant in totality. That implies that there is another variant in the LCT region unique to the Kalash. This also implies that the Eurasian variant has spread relatively recently into Northwest South Asia, perhaps post-dating the arrival of the Indo-Aryans! But the discussion is marred by the straightjacket of tree-thinking, imported from macroevolutionary contexts into a population genetic one, where it is less useful.
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