Population genetics of the Sami

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Since the early years of genetic research, the Sami people have caught the interests of scientists. The Sami languages belong to the Uralic languages family of Eurasia. Some older anthropologist have suggested they might be of Asian and/or Siberian origin. The frequency of blood group and protein polymorphisms in Sami differ significantly from the general Swedish population.[1]

In more recent years the use of mitochondrial DNA (mtDNA) and Y-DNA chromosomal markers has offered the opportunity for clarification of the origin of the Sami. While their mtDNA haplogroup distribution overwhelmingly represents a subset of the European gene-pool, the most common Y-DNA haplogroup among the Sami is widely believed to be of Eurasian origin and very common among all peoples in Northeastern Europe. The second most common haplogroup is I, which is found almost exclusively among those of European ancestry. Thus the Sami appear to have a complex population history, suggesting a mixture of peoples arriving in Fenno-Scandia at different times, from different directions. Their most common physical appearance is northern European like Finns or Scandinavians.[2]

mtDNA Haplogroups[edit]

Classification of the Sami mtDNA lineages revealed that the majority are clustered in a subset of the European mtDNA pool. The two haplogroups V and U5b dominate, between them accounting for about 89% of the total. This gives the Sami regions the highest level of Haplogroups V and U5b thus far found. Both haplogroups V and U5b are spread at moderate frequencies across Europe, from Iberia to the Ural Mountains. Haplogroups H, D5 and Z represent most of the remaining averaged total. Overall 98% of the Sami mtDNA pool is encompassed within haplogroups V, U5b, H, Z, and D5. Local frequencies among the Sami vary.[3] The divergence time for the Sami haplogroup V sequences was estimated by Max Ingman and Ulf Gyllensten at 7600 YBP (years before present), and for U5b1b1 as 5500 YBP amongst Sami and 6600 YBP amongst Sami and Finns. This suggests to them an arrival in the region soon after the retreat of the glacial ice.[4]

U5b[edit]

Although a small proportion of the Haplogroup U (mtDNA) among the Sami falls into U4, the great majority is U5b. The percentage of total Sami mtDNA samples tested by Tambets and her colleagues which were U5b ranged from 56.8% in Norwegian Sami to 26.5% in Swedish Sami.[3] Sami U5b falls into subclade U5b1b1. The Sami U5b1b1 [3] sub-clade is present in many different populations, e.g. 3% or higher frequencies in Karelia, Finland, and Northern-Russia.[3] The Sami U5b1 motif is additionally found in very low frequencies for instance in the Caucasus region, however this is explained as recent migration from Europe.[5] However 38% of the Sami U5b1b1 mtDNAs have haplotype so far exclusive to the Sami, containing a transition at np 16148.[3]

Alessandro Achilli and colleagues noted that the Sami and the Berbers share U5b1b, which they estimated at 9,000 years old, and argued that this provides evidence for a radiation of the haplogroup from the Franco-Cantabrian refuge area of southwestern Europe.[6]

V[edit]

As mentioned above, the divergence time for the Sami haplogroup V sequences was estimated by Max Ingman and Ulf Gyllensten at 7600 years ago.[4] Haplogroup V is by far the most frequent haplogroup in the Swedish Sami and is present at significantly lower frequencies in Norwegian and Finnish subpopulations.[3] Torroni and colleagues have suggested that the spread of haplogroup V in Scandinavia and in eastern Europe is due to its late Pleistocene/early Holocene expansion from a Franco-Cantabrian glacial refugium.[7]

However subsequent studies found that haplogroup V is also significantly present in eastern Europeans. Furthermore, haplogroup V lineages with HVS-I transitions 16153 and 16298 that are frequent in the Sami population are much more widespread in eastern than in western Europe. So haplogroup V might have reached Fennoscandia via central/eastern Europe. Such a scenario is indirectly supported by the absence, among the Sami, of the pre-V mtDNAs that are characteristic of southwestern Europeans and northwestern Africans.[3]

Z[edit]

Haplogroup Z is found at low frequency in the Sami and Northern Asian populations but is virtually absent in Europe. Several conserved substitutions group the Sami Z lineages with those from Finland and the Volga-Ural region of Russia. The estimated dating of the lineage at 2700 years suggests a small, relatively recent contribution of people from the Volga-Ural region to the Sami population.[4]

Y-DNA[edit]

Three Y chromosome haplogroups dominate the distribution among the Sami: N1c (formerly N3a), I1 and R1a. The most common haplogroup among the Sami is N1c, with I1 as a close second. Haplogroup R1a in Sami is mostly seen in the Swedish Sami and Kola Sami populations, with a low level among the Finnish Sami. Tambets and colleagues suggested that N1c and R1a probably reached Fennoscandia from eastern Europe, where these haplogroups can be found in high frequencies.[3]

However the two haplogroups have a distinctly different linguistic distribution. R1a1a is common among Eastern Europeans speaking Indo-European languages, while N1c correlates closely with the distribution of the Finno Ugrian languages. For example N1c is common among the Finns, while haplogroup R1a is common among all the neighbours of the Sami.[8] Haplogroup I1 is the most common haplogroup in Sweden, and the Jokkmokk Sami in Sweden have similar structure as among Swedes and Finns for haplogroup I1 and N1c.[9]

Gallery[edit]

See also[edit]

References[edit]

  1. ^ L.E. Beckman, K. Sjoberg, S. Eriksson and L. Beckman (2001). "Haemochromatosis gene mutations in Finns, Swedes and Swedish Saamis". Human Heredity 52 (2): 110–112. doi:10.1159/000053362. PMID 11474212. 
  2. ^ http://www.nordicway.com/search/Sami.htm
  3. ^ a b c d e f g h Kristiina Tambets, Siiri Rootsi, Toomas Kivisild, Hela Help, Piia Serk et al. (2004). "The Western and Eastern Roots of the Saami—the Story of Genetic "Outliers" Told by Mitochondrial DNA and Y Chromosomes". American Journal of Human Genetics 74: 661–682. doi:10.1086/383203. PMC 1181943. PMID 15024688. 
  4. ^ a b c Max Ingman and Ulf Gyllensten (2007). "A recent genetic link between Sami and the Volga-Ural region of Russia". European Journal of Human Genetics 15 (1): 115–120. doi:10.1038/sj.ejhg.5201712. PMID 16985502. 
  5. ^ Martin Richards et al. (2000). "Tracing European Founder Lineages in the Near Eastern mtDNA Pool". American Journal of Human Genetics 67: 1251–1276. doi:10.1016/S0002-9297(07)62954-1. PMC 1288566. PMID 11032788. 
  6. ^ Achilli, Saami and Berbers (2005). "An Unexpected Mitochondrial DNA Link". American Journal of Human Genetics 76: 883–886. doi:10.1086/430073. PMC 1199377. PMID 15791543. 
  7. ^ A. Torroni et al. (2001). "A signal, from human mtDNA, of postglacial recolonization in Europe". American Journal of Human Genetics 69: 884–885. doi:10.1086/323485. PMC 1226069. PMID 11517423. 
  8. ^ Tuuli Lappalainen, Satu Koivumäki, Elina Salmela, Kirsi Huoponen, Pertti Sistonen, Marja-Liisa Savontaus, Päivi Lahermo (2006). "Regional differences among the Finns: A Y-chromosomal perspective". Gene 376 (2): 207–215. doi:10.1016/j.gene.2006.03.004. PMID 16644145. 
  9. ^ Andreas O Karlsson, ThomasWallerström, Anders Götherström and Gunilla Holmlund (2006). "Y-chromosome diversity in Sweden – A long-time perspective". European Journal of Human Genetics 14 (8): 963–970. doi:10.1038/sj.ejhg.5201651. PMID 16724001.