The genetic prehistory of the New World Arctic.

The New World Arctic, the last region of the Americas to be populated by humans, has a relatively well-researched archaeology, but an understanding of its genetic history is lacking. We present genome-wide sequence data from ancient and present-day humans from Greenland, Arctic Canada, Alaska, Aleutian Islands, and Siberia. We show that Paleo-Eskimos (~3000 BCE to 1300 CE) represent a migration pulse into the Americas independent of both Native American and Inuit expansions. Furthermore, the genetic continuity characterizing the Paleo-Eskimo period was interrupted by the arrival of a new population, representing the ancestors of present-day Inuit, with evidence of past gene flow between these lineages. Despite periodic abandonment of major Arctic regions, a single Paleo-Eskimo metapopulation likely survived in near-isolation for more than 4000 years, only to vanish around 700 years ago.

Investigating the prehistory of Tungusic peoples of Siberia and the Amur-Ussuri region with complete mtDNA genome sequences and Y-chromosomal markers.

Evenks and Evens, Tungusic-speaking reindeer herders and hunter-gatherers, are spread over a wide area of northern Asia, whereas their linguistic relatives the Udegey, sedentary fishermen and hunter-gatherers, are settled to the south of the lower Amur River. The prehistory and relationships of these Tungusic peoples are as yet poorly investigated, especially with respect to their interactions with neighbouring populations. In this study, we analyse over 500 complete mtDNA genome sequences from nine different Evenk and even subgroups as well as their geographic neighbours from Siberia and their linguistic relatives the Udegey from the Amur-Ussuri region in order to investigate the prehistory of the Tungusic populations. These data are supplemented with analyses of Y-chromosomal haplogroups and STR haplotypes in the Evenks, Evens, and neighbouring Siberian populations. We demonstrate that whereas the North Tungusic Evenks and Evens show evidence of shared ancestry both in the maternal and in the paternal line, this signal has been attenuated by genetic drift and differential gene flow with neighbouring populations, with isolation by distance further shaping the maternal genepool of the Evens. The Udegey, in contrast, appear quite divergent from their linguistic relatives in the maternal line, with a mtDNA haplogroup composition characteristic of populations of the Amur-Ussuri region. Nevertheless, they show affinities with the Evenks, indicating that they might be the result of admixture between local Amur-Ussuri populations and Tungusic populations from the north.

Genetic structure of native circumpolar populations based on autosomal, mitochondrial, and Y chromosome DNA markers.

This study investigates the genetic structure of the present-day inhabitants of Beringia in order to answer questions concerning their origins and evolution. According to recent studies, the ancestors of Native Americans paused for a time in Beringia, during which they differentiated genetically from other Asians before peopling the New World. Furthermore, the Koryaks of Kamchatka share a "ubiquitous" allele (D9S1120) with Native Americans, indicating they may have descended from the same ancestral Beringian population that gave rise to the New World founders. Our results show that a genetic barrier exists between Kamchatkans (Koryaks and Even) and Bering Island inhabitants (Aleuts, mixed Aleuts, and Russians), based on Analysis of Molecular Variance (AMOVA) and structure analysis of nine autosomal short tandem repeats (STRs). This is supported by mitochondrial DNA evidence, but not by analysis of Y chromosome markers, as recent non-native male admixture into the region appears to have partially obscured ancient population relationships. Our study indicates that while Aleuts are descended from the original New World founders, the Koryaks are unlikely to represent a Beringian remnant of the ancestral population that gave rise to Native Americans. They are instead, like the Even, more recent arrivals to Kamchatka from interior Siberia, and the "ubiquitous" allele in Koryaks may result from recent gene flow from Chukotka. Genbank accession numbers for mtDNA sequences: GQ922935-GQ922973.

Genetic architecture of a small, recently aggregated Aleut population: Bering Island, Russia.

The fishing community of Bering Island, located in the Russian Commander Islands off the Kamchatka Peninsula, was originally founded by a small number of Russian soldiers and merchants, along with Aleuts forcibly relocated from the western region of the Aleutian archipelago. The purpose of this study is to characterize the genetic variation of Bering Island inhabitants for autosomal, mitochondrial, and Y-chromosome DNA and classic genetic markers and to investigate the genetic impact of the 19th-century founding and subsequent demographic events on this heterogeneous community. Our results show a loss of diversity among maternal lineages in the Bering Aleut population, with fixation of mtDNA haplogroup D, as revealed by median-joining network analysis and mismatch differences. Conversely, paternal haplotypes exhibit an increase in diversity and the presence of a substantial number of non-Native lineages. Admixture results, based on autosomal STR data, indicate that parental contributions to the mixed Aleut population of Bering are approximately 60% Aleut and 40% Russian. Classic genetic markers show affinities between the Bering Island Aleuts and the other historically founded Aleut communities of St. Paul and St. George in the Pribilof Islands, Alaska. This study demonstrates that the opposing evolutionary forces of genetic drift and gene flow acted on the maternal and paternal lineages, respectively, to shape the genetic structure of the present-day inhabitants of Bering Island.

Haplotype frequencies at the DRD2 locus in populations of the East European Plain.

BACKGROUND: It was demonstrated previously that the three-locus RFLP haplotype, TaqI B-TaqI D-TaqI A (B-D-A), at the DRD2 locus constitutes a powerful genetic marker and probably reflects the most ancient dispersal of anatomically modern humans. RESULTS: We investigated TaqI B, BclI, MboI, TaqI D, and TaqI A RFLPs in 17 contemporary populations of the East European Plain and Siberia. Most of these populations belong to the Indo-European or Uralic language families. We identified three common haplotypes, which occurred in more than 90% of chromosomes investigated. The frequencies of the haplotypes differed according to linguistic and geographical affiliation. CONCLUSION: Populations in the northwestern (Byelorussians from Mjadel'), northern (Russians from Mezen' and Oshevensk), and eastern (Russians from Puchezh) parts of the East European Plain had relatively high frequencies of haplotype B2-D2-A2, which may reflect admixture with Uralic-speaking populations that inhabited all of these regions in the Early Middle Ages.

Reduced fat oxidation and obesity risks among the Buryat of Southern Siberia.

Over the last 20 years, obesity and associated metabolic diseases have emerged as major global health problems. Among urbanizing populations of developing regions of the world, childhood undernutrition often coexists with adult overnutrition, a phenomenon known as the "dual nutritional burden". A recent work (Frisancho 2003: Am J Hum Biol 15:522-532) suggests that linear growth stunting in early childhood may contribute to adult obesity by reducing the body's ability to oxidize fat. We test central aspects of this model drawing on data from 112 adult Buryat herders (53 males; 59 females) from Southern Siberia. The results are consistent with the predictions of the model, but only for women. Shorter Buryat women (height-for-age Z-scores < or = -1) have significantly lower fasting fat oxidation levels compared to their taller counterparts. Shorter women are also significantly heavier and fatter, and have higher serum lipid levels. Among all Buryat women, reduced fat oxidation is significantly correlated with percent body fatness, serum triglyceride levels, and serum leptin levels, after controlling for relevant covariates. Additionally, Buryat women with high dietary fat intakes and low fat oxidation are significantly fatter and have higher lipid and leptin levels than those with low fat intakes and high fat oxidation. These results suggest that developmental changes in fat oxidation may play a role in the origins of obesity among populations with high rates of linear growth stunting. Further longitudinal research is necessary to elucidate the pathways through which early-life undernutrition may increase risks for adulthood obesity and cardiovascular disease.

Genetic structure of the Aleuts and Circumpolar populations based on mitochondrial DNA sequences: a synthesis.

The mtDNA variation of 198 Aleuts, as well as North American and Asian populations drawn from the literature, were analyzed to reconstruct the Aleuts' genetic prehistory and to investigate their role in the peopling of the Circumarctic region. From median-joining network analysis, three star-like clusters were identified in the Aleuts within the following subhaplogroups: A3, A7 (an Aleut-specific subclade of A3), and D2. Mismatch analyses, neutrality test scores, and coalescent time estimates for these three components provided evidence of two expansion events, one occurring at approximately 19,900 B.P. and the other at 5,400 B.P. Based on these findings and evidence from the archaeological data, four general models for the genetic prehistory of the Aleutian Island chain are proposed: 1) biological continuity involving a kin-structured peopling of the archipelago; 2) intrusion and expansion of a non-native biface-producing population dominated by subhaplogroup D2; 3) amalgamation of Arctic Small Tool tradition peoples characterized by D2 with an older Anangula substratum; and 4) biological continuity with significant gene flow from neighboring populations of the Alaskan mainland and Kodiak Island. The Aleut mtDNAs are consistent with the Circumarctic pattern by the fixation of A3 and D2, and the exhibition of depressed diversity levels relative to Amerind and Siberian groups. The results of this study indicate a broad postglacial reexpansion of Na-Dene and Esko-Aleuts from reduced populations within northern North America, with D2 representing a later infusion of Siberian mtDNAs into the Beringian gene pool.

Genetic analysis of reproduction in the Buryat populations.

A complex anthropological survey based on population-genetic methods and a study of a wide spectrum of genetic systems (43 alleles from 17 independent loci) was undertaken among 450 Buryat women of post-reproductive age. The results obtained showed the influence of particular genetic markers and their complex on the formation of peculiarities in the reproduction structure of the Buryat population.A sharp increase in phenotype GC 2-2 frequency and the corresponding GC*2 allele of the group-specific component (GC) was established for women groups with burdened obstetric records. These groups are characterized also by a considerable decrease in the observed geterozygosity (Ho) as compared to its expected value (He). Samples including women with multiple pregnancies in the recorded obstetric anamnesis are characterized by a significant increase in the frequency of the rare alleles TF*C3 of the transferrin system and those of PI*Z belonging to the proteinase inhibitor system (a1-antitrypsin) as compared to the control group. The results obtained widened current knowledge about the influence of genetic and environmental components on reproduction processes in human populations.

Mitochondrial DNA evidence for admixed origins of central Siberian populations.

The Yakuts of northeastern Siberia are a Turkic-speaking population of horse- and cattle-breeders surrounded by Tungusic-speaking reindeer-herders and hunter-gatherers. Archaeological and ethnohistorical data suggest that Yakuts stem from a common ancestral population with the Buryats living near Lake Baikal. To address this hypothesis, we obtained sequences of the first hypervariable segment (HV1) of the mitochondrial DNA control region from Yakuts and Buryats and compared these with sequences from other Eurasian populations. The mtDNA results show that the Buryats have close affinities with both Central Asian Turkic groups and Mongols, while the Yakuts have close affinities with northeastern Siberian, Tungusic-speaking Evenks and south Siberian, Turkic-speaking Tuvans. This different ancestry of the Yakuts and the Tuvans (compared with other Turkic-speaking groups) most likely reflects extensive admixture that occurred between Turkic-speaking steppe groups and Evenks as the former migrated into Siberia. Moreover, the Yakuts are unique among Siberian populations in having a high number of haplotypes shared exclusively with Europeans, suggesting, contrary to the historical record, that occasionally Yakut men took Russian women as wives.

Climatic influences on basal metabolic rates among circumpolar populations.

This article examines evidence for elevations in basal metabolic rate (BMR) among indigenous Northern (circumpolar) populations and considers potential mechanisms and the adaptive basis for such elevations. Data on BMR among indigenous (n = 109 males; 122 females) and nonindigenous (n = 15 males; 22 females) circumpolar groups of North America and Siberia are compiled and compared to predicted BMRs based on three different references: body surface area (Consolazio et al., 1963), body mass (Schofield, 1985), and fat-free mass (Poehlman and Toth, 1995). Regardless of which reference is used, indigenous circumpolar groups show systematic and statistically significant elevations in BMR ranging from +7% to +19% above predicted values for indigenous men and from +3 to +17% for indigenous women. Nonindigenous males also show elevations in BMR, although not to the same extent as in indigenous men (deviations = +3 to +14%), whereas nonindigenous females show no clear evidence of elevated BMRs (deviations = -7 to +5%). This pattern of variation between indigenous and nonindigenous groups suggests that both functional and genetic factors play a role in metabolic adaptation to northern climes. Recent studies on the ecology and genetics of thyroid function offer insights into the mechanisms through which indigenous circumpolar populations may regulate metabolic rates. Studies of seasonal variation in thyroid hormone levels suggest that indigenous circumpolar populations may have a greater capacity to elevate BMR during severe cold than nonindigenous groups. Recent twin studies indicate a significant genetic component of thyroid responses to environmental stressors. Further research exploring the genetics of seasonal variation in thyroid function and BMR among circumpolar groups would advance understanding of the role that selection may have played in shaping metabolic variation.

Analysis of CCR5Delta32 geographic distribution and its correlation with some climatic and geographic factors.

We studied the possible effects of climatic-geographic factors on the world distribution of the mutant allele for the chemokine receptor gene CCR5, which has a 32-bp deletion (CCR5Delta32) preventing cell invasion by the primary transmitting strain of HIV-1. New data on CCR5 polymorphisms in Russian, Ukrainian, and Moldavian populations are presented. All available data on CCR5Delta32 frequencies in the Old World (number of populations n = 77) were used for construction of a geographical gene map to analyze possible correlations between allele frequencies and eight climatic-geographic parameters. A strong positive correlation was found between the allele frequency and latitude (r = 0.72), a strong negative correlation with annual radiation balance (r = -0.66), and a weaker negative correlation with longitude (r = -0.34). Partial correlations were calculated excluding the influence of latitude. The negative correlation between the allele frequency and annual radiation balance decreased (r = -0.42), but remained large and significant. We propose that the existence of correlations between the cline of CCR5Delta32 frequencies and climatic-geographic parameters provides evidence for a possible effect of either natural environmental factors or large-scale population movements on the distribution of this allele.