Genetic clues to the Ossetian past
[Many thanks to Dave Howard for his assistance with this post!]
While it is indisputable that Ossetians speak an Iranian language, it is not immediately apparent whether they descend from an Iranian group such as the Alans, or alternatively if they are descendants of one of the autochthonous groups from the Caucasus, which adopted an Iranian language in the early Middle Ages or possibly even earlier; according to this second theory, prior to the adoption of an Iranian language, the Ossetians spoke some Caucasian language (more on which one below). Recent genetic studies seem to confirm both of these hypotheses since different research teams come up with dissimilar and often contradictory results. In this post, we will try to unravel some of these complex data and conclusions.
An earlier study on the Ossetian DNA was conducted by Ivan Nasidze and his colleagues from the Max Planck Institute for Evolutionary Anthropology in Leipzig, the Center of Integrative Genomics at the University of Lausanne and the Vavilov Institute of General Genetics in Moscow, and its results published in a 2004 article in Annals of Human Genetics. This team concluded that a common origin of Ossetians is from an Iranian group, followed by subsequent influx of mostly males from the neighboring Caucasian tribes. According to this team’s findings, mitochondrial DNA data, which traces maternal descent, suggests a common origin for North and South Ossetians, as well as their close affinity with other Iranian groups. In contrast, the Y‑DNA data, which traces paternal descent, indicates that North Ossetians are more similar to other North Caucasian groups, and South Ossetians are more similar to other South Caucasian groups, than to each other. In human terms, these findings translate into the following picture: Iranian-speaking Alan women marrying local Caucasian men.
However, while it makes sense that the Ossetians would intermarry with other groups on their respective slopes of the Caucasus mountains, the conclusion that Iranian-speaking women intermarried with Caucasian men challenges everything we know about the interactions of nomadic pastoralists (in this case, Iranian-speaking Alans) with sedentary groups (in this case, the indigenous Caucasian groups).
This theory also contradict the overall picture that emerges from other instances of gender-specific migration and language shift: according to a recent study, conducted by Peter Forster and Colin Renfrew of the University of Cambridge, “language change among our prehistoric ancestors came about via the arrival of immigrant men — rather than women — into new settlements”. In other words, more often than not it is women who adopt their husbands’ tongue, rather than the other way around. If present-day Ossetians descended from (mostly) Iranian mothers and Caucasian fathers, we’d expect them to speak a Caucasian rather than an Iranian language, contrary to the fact.
There are also some methodological problems with Nasidze et al.’s article. Generally speaking, they took a very zoomed-out view of the Ossetians’ DNA: for instance, they examined only a small portion of the mitochondrial DNA (HVR1 region of about 400 base pairs out of 16,569 base pairs); and as far as Y-DNA is concerned, they did not look further downstream than the mutation that defines Haplogroup F, thus potentially missing some connections between North and South Ossetian men.
More recent studies, such as the study from a team of geneticists, anthropologists and linguists, published in Molecular Biology and Evolution (see Balanovsky 2011), also challenged Nasidze et al.’s conclusions. Balanovsky et al.’s study focused on the Y-DNA from several ethno-linguistic groups in the North Caucasus; as far as the Ossetians are concerned, only the Y-DNA of North Ossetians was examined, but this study used a larger number of individual samples (357 samples from Ossetians alone). Rather than find much Y-DNA in common with other Caucasian groups, Balanovsky’s team claims that most Ossetian men carry a certain genetic signature that is common to them alone. Specifically, they found that at least 56% of Ossetian men (and up to 73% among the Iron) share haplogroup G2a1a-P18 (which is a subgroup of G2a1-P16 shown in blue in pie charts in the map below).* This haplogroup is found on average in only 3% of males in other Caucasian groups (the two other group that has a relatively high frequency of this haplogroup are the Abkhazians and the Circassians, with 12% and 9% respectively).
The Ossetians’ neighbors to the west, speakers of Northwest Caucasian languages – the Shapsugs, the Circassians, and the Abkhasians – belong predominantly to haplogroup G2a3b1-P303 (shown in yellow in pie charts in the map below). The frequency of this haplogroup among speakers of Northwest Caucasian languages ranges from 21% among the Abkhaz to 86% among the Shapsugs, while it is found only in 3% of the Ossetians. To the east of the Ossetians we find speakers of Nakh languages (Chechen and Ingush), who belong predominantly to haplogroup J2a4b-M67(xM92), shown in red in pie charts in the map below; and of Dagestanian languages (among them Dargin, Avar, Kaitag, Kubachi, and Lezgi were tested), who belong predominantly to haplogroup J1-M267(xP58), shown in green in pie charts in the map below. The frequency of these two haplogroups among the Ossetians is 8.4% and 2.6% respectively. In other words, the Ossetians do not share much Y-DNA with their neighbors in the North Caucasus, according to this more recent study by Balanovsky et al.
Another piece is added to the puzzle if we consider more closely what sorts of mutations the Ossetian men share. Their most common genetic signature – G2a1a – is characterized by the presence of single-nucleotide polymorphism (SNP) known as P18. However, the Ossetians also share another genetic signature: 10 short tandem repeats (STRs) at position DYS392. Unlike SNPs, whose rate of mutation is measured in thousands of years, the rate of STR mutations is much more rapid (this is why STRs are an important tool for both tracing genealogical ancestry and for determining genetic profiles in forensic cases). Having such a high concentration of Ossetian men with the same STR count means that the group built up rather rapidly over the last 1,500 years or less. This is compatible with the hypothesis that the Ossetians are descendants of a small number of (possibly related) male invaders, contra Nasidze et al. (2004). Alternatively, if a later date is assumed, the Ossetian men may be hypothesized to be descendants of a small group who survived the genetic bottleneck associated with the destruction of Alania by Tamerlane in the late 1300s.
Balanovsky et al.’s study also allows us to hazard a guess as to what kind of language the ancestors of present-day Ossetians spoke before being acculturated by the Iranian-speaking Alans. Balanovsky et al.’s study confirms that common language serves as a bridge for gene flow between populations; for example,
“Circassians, who are geographically situated between Adyghes and Ossets, might receive more gene flow from Adyghes, who speak a similar language, than from Ossets who differ in their language and culture.” (pp. 2915-2916)
Since the Ossetians are separated from their eastern neighbors by a more significant genetic boundary (line A on the map above) than from their western neighbors (line C on the map above), it stands to reason that the ancestors of the Ossetians spoke a Northwest Caucasian language, likely a closer relative of Kabardian or Circassian.
But the plot thickens if we consider the question of where these haplogroup G2a1a Ossetian males might have come from. If we believe that this genetic signature among the Ossetian males comes from the Alans, it is expected that the Alans (or their predessors the Scythians/Sarmatians) must also have been high in haplogroup G2a1a, or its ancestral clade G. Moreover, certain areas of Europe to which large numbers of Alans and other Sarmatians migrated also feature a higher frequency of haplogroup G. However, the subtype of haplogroup G found in these European areas is not the expected Ossetian G2a1a, nor the G2a3b1, common among the Kabardinians of the northwestern Caucasus adjacent to the Ossetians. Furthermore, examination of ancient DNA from what is thought to be Scythian skeletons from the south Siberian steppes to the northeast of the Caucasus has found only haplogroup R1a1-M17, common in Eastern Europe, parts of Central and Northern Asia. According to Keyser et al. (2009), this haplogroup is the “mark [of] the eastward migration of the early Indo-Europeans”. But if the Scythians/Sarmatians were high in haplogrop R1a1 (and not G), why aren’t more Ossetians in haplogroup R1a1 (which is practically not found in the Ossetian population at all)? Is it the case that (the majority of) Ossetian male ancestors came from an indigenous Caucasian group after all?
And so the mystery of the Ossetians’ past remains…
*Subgroups are numbered by adding alternative numbers and letters: for example, haplogroup G2a1a is a subgroup of G2a1, which is in turn a subgroup of G2a, which is a subgroup of G2, itself a subgroup of G. The large haplogroups numbered by one letter are not necessarily independent either: for example, haplogroup G is a subgroup of F (see chart below). The letters and numbers after a hyphen refer to the defining mutation. For example, haplogroup G is defined by mutation M201, whereas haplogroup G2a1a is defined by mutation P18.
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Balanovsky, Oleg; Khadizhat Dibirova; Anna Dybo; Oleg Mudrak; Svetlana Frolova; Elvira Pocheshkhova; Marc Haber; Daniel Platt; Theodore Schurr; Wolfgang Haak; Marina Kuznetsova; Magomed Radzhabov; Olga Balaganskaya; Alexey Romanov; Tatiana Zakharova; David F. Soria Hernanz; Pierre Zalloua; Sergey Koshel; Merritt Ruhlen; Colin Renfrew; R. Spencer Wells; Chris Tyler-Smith; Elena Balanovska; and The Genographic Consortium (2011) Parallel Evolution of Genes and Languages in the Caucasus Region. Molecular Biology and Evolution 28(10): 2905–2920.
Keyser C., Bouakaze C., Crubézy E., Nikolaev V.G., Montagnon D., Reis T., Ludes B. (2009) Ancient DNA provides new insights into the history of south Siberian Kurgan people. Human Genetics 126(3): 395-410. http://www.ncbi.nlm.nih.gov/pubmed/19449030
Nasidze, Ivane S.; Dominique Quinque, Isabelle Dupanloup, Sergey Rychkov, Oksana Naumova, Olga Zhukova and Mark Stoneking (2004) Genetic Evidence Concerning the Origins of South and North Ossetians. Annals of Human Genetics 68: 588-599.
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