Sami people, also spelled Sámi, or Saami are the arctic indigenous people inhabiting Sápmi, which today encompasses parts of far northern Sweden, Norway, Finland and the Kola Peninsula of Russia, but also in the border area between south and middle Sweden and Norway. The Sámi are Europe’s northernmost and the Nordic countries’ only officially indigenous people. Sami ancestral lands span an area of approximately 388,350 km2 (150,000 sq. mi) which is comparatively about the size of Sweden in the Nordic countries. Their traditional languages are the Sami languages. The Sami languages are endangered, and are classified as a branch of the Uralic language family.
Traditionally, the Sami have plied a variety of livelihoods, including coastal fishing, fur trapping, and sheep herding. Their best known means of livelihood is semi-nomadic reindeer herding – which about 10% of the Sami are connected with and 2,800 actively involved with full-time. For traditional, environmental, cultural, and political reasons, reindeer herding is legally reserved only for Sami people in certain regions of the Nordic countries.
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.
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.
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. 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.
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. Sami U5b falls into subclade U5b1b1. The Sami U5b1b1  sub-clade is present in many different populations, e.g. 3 % or higher frequencies in Karelia, Finland, and Northern-Russia. 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. However 38% of the Sami U5b1b1 mtDNAs have haplotype so far exclusive to the Sami, containing a transition at np 16148.
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.
As mentioned above, the divergence time for the Sami haplogroup V sequences was estimated by Max Ingman and Ulf Gyllensten at 7600 years ago. 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. 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.
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.
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. 
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.
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. 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.
Y-DNA haplogroups by ethnic groups
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^ 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.
^ 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.
^ 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.
^ 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.
^ 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.
^ 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.
^ 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.
The sequencing of entire human mitochondrial DNAs belonging to haplogroup U reveals that this clade arose shortly after the “out of Africa” exit and rapidly radiated into numerous regionally distinct subclades. Intriguingly, the Saami of Scandinavia and the Berbers of North Africa were found to share an extremely young branch, aged merely ?9,000 years. This unexpected finding not only confirms that the Franco-Cantabrian refuge area of southwestern Europe was the source of late-glacial expansions of hunter-gatherers that repopulated northern Europe after the Last Glacial Maximum but also reveals a direct maternal link between those European hunter-gatherer populations and the Berbers.
Saami and Berbers—An Unexpected Mitochondrial DNA Link
Alessandro Achilli,1 Chiara Rengo,1 Vincenza Battaglia,1 Maria Pala,1 Anna Olivieri,1 Simona Fornarino,1 Chiara Magri,1 Rosaria Scozzari,2 Nora Babudri,3 A. Silvana Santachiara-Benerecetti,1 Hans-Jürgen Bandelt,4 Ornella Semino,1 and Antonio Torroni1
1Dipartimento di Genetica e Microbiologia, Università di Pavia, Pavia, Italy; 2Dipartimento di Genetica e Biologia Molecolare, Università “La Sapienza,” Rome; 3Dipartimento di Biologia Cellulare e Ambientale, Università di Perugia, Perugia, Italy; and 4Fachbereich Mathematik, Universität Hamburg, Hamburg
Address for correspondence and reprints: Dr. Antonio Torroni, Dipartimento di Genetica e Microbiologia, Università di Pavia, Via Ferrata 1, 27100 Pavia, Italy. E-mail: email@example.com
Received January 21, 2005; Accepted March 3, 2005.
Because of maternal transmission and lack of recombination, the sequence differentiation of human mtDNA has been generated by only the sequential accumulation of new mutations along radiating maternal lineages. Over the course of time, this process of molecular divergence has given rise to monophyletic units that are called “haplogroups.” Because this process of molecular differentiation occurred mainly during and after the process of human colonization of and diffusion into the different continents and regions, haplogroups and subhaplogroups tend to be restricted to specific geographic areas and population groups (Wallace 1995; Achilli et al. 2004).
Only the founders of the sister superhaplogroups M and N (which includes haplogroup R) (Quintana-Murci et al. 1999) participated in the “out of Africa” exit (Cann et al. 1987; Stringer and Andrews 1988; Cavalli-Sforza et al. 1994; Underhill et al. 2000; Forster et al. 2001) and were successful in colonizing the rest of the Old World. Superhaplogroup N is globally distributed outside Africa, encompassing virtually all of the western Eurasian mtDNA variation, and embraces haplogroup U, nested in haplogroup R. Haplogroup U has an extremely broad geographic distribution that ranges from Europe and North Africa to India and Central Asia and has a very high overall frequency (15%–30%) (Richards et al. 2000; Kivisild et al. 2003; Quintana-Murci et al. 2004)
To assess the nature and extent of haplogroup U variation, we initially sequenced 28 entire U mtDNAs (see authors’ Web site and GenBank) from a wide range of populations. These were selected through a preliminary sequence analysis of the mtDNA control region to include the widest possible range of haplogroup U internal variation. A tree of the mtDNA sequences (fig. 1) reveals that haplogroup U first splits into two major subsets, distinguished by the mutation at nt 1811, and that there is a very large number of independent basal branches. Among these, representatives of all known subhaplogroups (U1–U9) were included. However, subhaplogroup U5 provided a rather intriguing result. A Yakut from northeastern Siberia (27 in fig. 1) and a Fulbe from Senegal (29 in fig. 1) harbored mtDNAs that differed at only two coding-region nucleotide positions.
Tree of 39 mtDNA sequences belonging to haplogroup U. The tree, rooted using the reference sequence (rCRS) (Andrews et al. 1999) as an outgroup, illustrates subhaplogroup affiliations. The sequencing procedure and phylogeny construction were performed (more …)
To investigate this striking similarity, the portion of the tree encompassing these two mtDNAs was enriched by sequencing 11 additional mtDNA sequences (22–26, 28, 30, 32, 34, 36, and 37 in fig. 1) bearing the control-region motif 16270-150, a motif found generally at low frequencies (<2%) in Berber populations and in other African groups (such as the Fulbe) known to have intermingled with Berbers (Rosa et al. 2004). The motif also shows similarly low frequencies in virtually all European populations, except the Saami of northern Scandinavia, in which it reaches ?48% (Tambets et al 2004). Because virtually all Saami mtDNAs with 16270-150 harbor the transitions at nts 16189 and 16144 seen in the Yakut mtDNA, three Saami mtDNAs were included among the additional samples.
Seven of the new sequences (one Berber from Algeria, two Italian, one Spanish, and three Saami) clustered into U5b1b, the subclade encompassing the Yakut and Fulbe mtDNAs. The Saami and the Yakut mtDNAs formed a minor branch distinguished only by the transition at nt 16144, the Berber and the Fulbe mtDNAs clustered in a second minor branch also characterized only by control-region mutations, and the Italian and Spanish mtDNAs formed other minor branches.
The average sequence divergence (± SE, computed as per Saillard et al. ) of the 39 coding-region sequences from the root of haplogroup U was 11.4 ± 1.3 substitutions (disregarding indels and pathological mutations), a value which corresponds—according to the mutation-rate estimate of Mishmar et al. (2003)—to a coalescence time estimate of 58.8 ± 6.8 thousand years (ky) for the entire haplogroup U. This value agrees well with the corresponding estimate of 61.6 ± 12.5 ky, based on the hypervariable segment I (HVS-I) mutation rate (Forster et al. 1996), for these 39 mtDNAs. An age of ?60 ky indicates that haplogroup U arose very soon after the “out of Africa” exit. As for U5, its sequence divergence was 8.1 ± 1.8 substitutions, corresponding to 41.4 ± 9.2 ky, a time estimate in full agreement with its proposed proto-European origin (Richards et al. 2000). It is striking that the sequence divergence of U5b1b, the subclade encompassing mtDNAs from the Saami, Yakut, Berbers, and Fulbe, was 1.7 ± 0.5 substitutions, thus corresponding to only 8.6 ± 2.4 ky.
Such a recent common ancestry of maternal lineages found in populations living as far as 9,000 miles apart and whose anthropological affinities are not at all obvious is, to say the least, unexpected. Can we provide a reasonable explanation? The recent molecular dissection of other mtDNA haplogroups reveals some clues. H1 and H3, two frequent subhaplogroups of H, display frequency peaks centered in Iberia and surrounding populations, including the Berbers of Morocco, and coalescence ages of ?11 ky (Achilli et al. 2004). Furthermore, their frequency patterns and ages resemble those reported for haplogroup V (Torroni et al. 2001a)—which, similar to U5b1b, is extremely common only in the Saami (together, U5b1b and V encompass almost 90% of the Saami mtDNAs) (Torroni et al. 1996; Tambets et al. 2004). Thus, although these previous studies have highlighted the role of the Franco-Cantabrian refuge area as a major source of the hunter-gatherer populations that gradually repopulated much of central and northern Europe when climatic conditions began to improve ?15 ky ago, the identification of U5b1b now unequivocally links the maternal gene pool of the ancestral Berbers to the same refuge area and indicates that European hunter-gatherers also moved toward the south and, by crossing the Strait of Gibraltar, contributed their U5b1b, H1, H3, and V mtDNAs to modern North Africans.
In conclusion, this study is a paradigmatic example of the power of genetic inference in human-origin and evolutionary studies. It shows that mtDNA data—in this case, at the highest possible level of molecular resolution—can be used not only to evaluate models proposed by other disciplines and based on the direct survey of ancient material but also to identify previously unknown links between populations and geographic areas. Thus, the study of human genetics directly fosters the development of new research avenues in paleontology, archaeology, linguistics, and history.
This research was supported by CNR-MIUR Genomica Funzionale-Legge 449/97, Fondo Investimenti Ricerca di Base 2001, the Istituto Pasteur Fondazione Cenci Bolognetti, and Progetti Ricerca Interesse Nazionale 2003.
Accession numbers and URLs for data presented herein are as follows:
Author’s Web site, http://ipvgen.unipv.it/docs/projects/torroni_data/torroni_sequences.html (for the complete mtDNA sequences)
GenBank, http://www.ncbi.nlm.nih.gov/Genbank/ (for the complete mtDNA sequences [accession numbers AY882379–AY882417])
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