Резултати в Българския ДНК проект -2 / Наука / Природни науки / Генетика

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Genetic origins[edit]

See also: Genetic history of Europe

The study of Y-DNA haplogroups has received the most attention. Bulgarians, like their immediate neighbours (Macedonians, Romanians) show the highest diversity of haplogroups in Europe, marked by significant (> 10%) frequencies of 5 major haplogroups (compared to Atlantic Europe, dominated by > 90% R1b, and eastern Europe, dominated by R1a1). The major haplogroups are: [63]
R1a: several subclades have now been identified at levels ~ 18% (Karachanak 2013). The M-458 branch, which is very common in Poland and other West Slavic countries is present in Bulgaria at 7.5% (Karachanak 2013), whilst its frequency of 40% in Hungary (Carpathian basin) (Pamjav 2012). The remaining branches (10%) might belong to the older Z – 280 (“Central Eurasian”), as well as perhaps the even more ancient “Old European” branch (Klyosov 2012), although Bulgarians have not yet been formally tested for these subhaplogroup SNPs.

R1b: Present in Bulgarians ~ 11% (Karachanak 2013). R1b is represented by several subclades. Some show western European affinities, whilst the R-L23* branch shows a clear relationship with Anatolia and the Near East (Cruciani 2010)(Klyosov 2012). At present, the overall evidence suggests that the macro-haplogroup R arose somewhere in southern or central Asia, perhaps northern India. Their subsequent path into Europe, and exact timing of spread requires further fine resolution studies; however a Balkan entry into Europe seems highly probable. Their overall ages depend on which 'mutation rate' is used – the 'evolutionary effective' rate advocated by Zhivotovsky et al. (and used by 'population geneticists'), versus the 'germline mutation' rate used by most genetic genealogists. The difference translates into different putative epochs of entry – Last Glacial Maximum (Underhill 2009) versus the Holocene (Klyosov 2009).

Haplogroup I is presented at levels ~ 27% (Karachanak 2013). Evidence points to a Levantine origin for haplogroup I, or perhaps its immediate ancestor- IJ. The age of Hg I (22 kya), its exclusive and now patchy distribution within Europe suggests a very early entry in to Europe; perhaps with Palaeolithic colonization. However, subsequent events have shaped its current distribution – such as the expansion of R1b in Western Europe, R1a in Eastern Europe, as well as additional haplogroups in south-eastern Europe, almost eradicating it. Balkan Hg I belongs specifically to the P37.2, M423 branch ("Hg I2a1b3"). Its most closely related to a branch (Hg I2a1b2) is only found in the British Isles. A more distant relative, which split several thousand years ago, is the "Sardinian" haplogroup I2a1 (P37.2, M423 also). Initially Rootsi supposed a Holocene expansion of I2 in SEE (Rootsi 2004); however the homogeneity of Balkan Hg I2 and its star-like clustering suggests a far more recent expansion time. It was confirmed later that I2 started to resettle Eastern Europe only around 2,300 YBP.(Klyosov 2013)

Haplogroup E-V68 is presented at levels ~ 22% (Karachanak 2013). The ultimate origin of E-V68 points to northeastern Africa, specifically near the Nile and Lake Alexandria (Cruciani 2004). Thus this haplogroup represents a more recent “out of Africa” movement into the Balkans. How and when it entered the Balkans is less clear, however Cruciani et al propose a Holocene movement into the Near East, then several thousand years ago, a movement into the Balkans (Cruciani 2004). Recent findings of V13 in a Neolithic context in Iberia (dated to ~ 7 kya) give a terminus ante quem (Lacan 2011). Like M423 above, however, it might have really begun to expand in the Balkans somewhat later, perhaps during the population growth of the Bronze Age, according to Cruciani.

Haplogroup J2 is also presented at leve ls ~ 11% (Karachanak 2013). Whilst its origin is north Levantine, its current pattern reflects more recent events connecting the Aegean and western Anatolia during the Copper and Bronze Ages, as well as possibly historic Greek colonization. There are several subclades within J2 : J2a M410, J2b M12, M67 and M92 (Semino 2004, Di Giacomo 2003).
Finally, there are also some other Y-DNA Haplogroups presented at a lower levels among Bulgarians ~ 10% all together, as G, J1 and T (Karachanak 2013).
Complimentary evidence exists from mtDNA data. From this perspective, Bulgaria shows a very similar profile to other European countries – dominated by mitochondrial haplogroups Hg H (~42%), Hg U (~22%), Hg T (~11%), Hg J (~8%) and Hg K (~6%) (Karachanak 2012). Recent studies show greater diversity within mt Haplogroups than once thought, as sub-haplogroups are being discovered. For example, within the apparently homogeneous European presence of Hg H, subcluster H1 is more prevalent in western Europe (especially Iberia), whilst subclusters H1b and H2a are more common in Eastern Europeans (Loogvali 2004).

Overall[edit]
Further evidence from ancient DNA, reconsiderations of mutation rates, and collateral evidence from autosomal DNA growth rates suggest that the major period of European population expansion occurred after the Holocene. Thus the current geographic spread and frequency of haplogroups has been continually shaped from the time of Palaeolithic colonization to beyond the Neolithic (Pinhasi 2012)(Ricaut 2012). This process of genetic shaping continued into recorded history, such as the Slavic migrations.(Rower 2005)(Ralph 2012)

It is important to note that, whilst haploid markers such as mtDNA and Y-DNA can provide clues about past population history, they only represent a single genetic locus, compared to hundreds of thousands present in nuclear, autosomal chromosomes. Analyses of autosomal DNA markers gives the best approximation of overall 'relatedness' between populations, presenting a less skewed genetic picture compared to Y DNA haplogroups. This atDNA data shows that there are no sharp discontinuities or clusters within the European population. Rather there exists a genetic gradient, running mostly in a southeast to northwest direction. Overall, Bulgarians are closest to Macedonians, Romanians and Serbians; followed by other Balkan populations such as Croats, Albanians and Greeks. Bulgarians are more distantly related to other fellow Slavic-speaking countries such as Russians and Poles. Moreover, they were only modestly close to their immediate eastern neighbours – the Turks- suggesting the presence of certain geographic and cultural barriers (Novembre 2008)(Yanusbaev 2012).

Recent studies of ancient DNA have revealed that European populations are largely descending from three ancestral groups. The first one are Paleolithic Siberians, the second one are hunter-gatherers from Northern European type, and the third one are Early farmers and later arrivals from West Asia. According to this, Bulgarians are predominantly (~70%) descending from early Neolithic farmers spreading the agriculture from Anatolia, and from West Asian Bronze age invaders and cluster together with other Southern Europeans. One of the admixture signal in that farmers involves some ancestry related to East Asians, with ~ 2% total Bulgarian ancestry proportion linking to a presence of nomadic groups in Europe, from the time of the Huns to that of the Ottomans. A second signal involves admixture between the North European group from one side and the West Asian - Early farmers' group from another side, at approximately the same time as the East Asian admixture, ca. 850 AD. The second event may correspond to the expansion of Slavic language speaking people. The analysis documents this admixture in Bulgarians at a level from ca. 28%.[64]