Archaeological Support for the Three-Stage Expansion of Modern Humans across Northeastern Eurasia and into the Americas

Background

Understanding the dynamics of the human range expansion across northeastern Eurasia during the late Pleistocene is central to establishing empirical temporal constraints on the colonization of the Americas [1]. Opinions vary widely on how and when the Americas were colonized, with advocates supporting either a pre-[2] or post-[1], [3], [4], [5], [6] last glacial maximum (LGM) colonization, via either a land bridge across Beringia [3], [4], [5], a sea-faring Pacific Rim coastal route [1], [3], a trans-Arctic route [4], or a trans-Atlantic oceanic route [5]. Here we analyze a large sample of radiocarbon dates from the northeast Eurasian Upper Paleolithic to identify the origin of this expansion, and estimate the velocity of colonization wave as it moved across northern Eurasia and into the Americas.

Methodology/Principal Findings

We use diffusion models [6], [7] to quantify these dynamics. Our results show the expansion originated in the Altai region of southern Siberia ∼46kBP , and from there expanded across northern Eurasia at an average velocity of 0.16 km per year. However, the movement of the colonizing wave was not continuous but underwent three distinct phases: 1) an initial expansion from 47-32k calBP; 2) a hiatus from ∼32-16k calBP, and 3) a second expansion after the LGM ∼16k calBP. These results provide archaeological support for the recently proposed three-stage model of the colonization of the Americas [8], [9]. Our results falsify the hypothesis of a pre-LGM terrestrial colonization of the Americas and we discuss the importance of these empirical results in the light of alternative models.

Conclusions/Significance

Our results demonstrate that the radiocarbon record of Upper Paleolithic northeastern Eurasia supports a post-LGM terrestrial colonization of the Americas falsifying the proposed pre-LGM terrestrial colonization of the Americas. We show that this expansion was not a simple process, but proceeded in three phases, consistent with genetic data, largely in response to the variable climatic conditions of late Pleistocene northeast Eurasia. Further, the constraints imposed by the spatiotemporal gradient in the empirical radiocarbon record across this entire region suggests that North America cannot have been colonized much before the existing Clovis radiocarbon record suggests.     

Genetic diversity and phylogeography of broomcorn millet (Panicum miliaceum L.) across Eurasia

Broomcorn millet (Panicum miliaceum L.) is one of the world's oldest cultivated cereals, with several lines of recent evidence indicating that it was grown in northern China from at least 10,000 cal bp. Additionally, a cluster of archaeobotanical records of P. miliaceum dated to at least 7000 cal bp exists in eastern Europe. These two centres of early records could either represent independent domestications or cross-continental movement of this cereal that would predate that of any other crop by some 2 millennia. Here, we analysed genetic diversity among 98 landrace accessions from across Eurasia using 16 microsatellite loci, to explore phylogeographic structure in the Old World range of this historically important crop. The major genetic split in the data divided the accessions into an eastern and a western grouping with an approximate boundary in northwestern China. A substantial number of accessions belonging to the 'western' genetic group were also found in northeastern China. Further resolution subdivided the western and eastern genepools into 2 and 4 clusters respectively, each showing clear geographic patterning. The genetic data are consistent with both the single and multiple domestication centre hypotheses and add specific detail to what these hypotheses would entail regarding the spread of broomcorn millet. Discrepancies exist between the predictions from the genetic data and the current archaeobotanical record, highlighting priorities for investigation into early farming in Central Asia.     

The Genetic Legacy of the Pre-Colonial Period in Contemporary Bolivians

Only a few genetic studies have been carried out to date in Bolivia. However, some of the most important (pre)historical enclaves of South America were located in these territories. Thus, the (sub)-Andean region of Bolivia was part of the Inca Empire, the largest state in Pre-Columbian America. We have genotyped the first hypervariable region (HVS-I) of 720 samples representing the main regions in Bolivia, and these data have been analyzed in the context of other pan-American samples (>19,000 HVS-I mtDNAs). Entire mtDNA genome sequencing was also undertaken on selected Native American lineages. Additionally, a panel of 46 Ancestry Informative Markers (AIMs) was genotyped in a sub-set of samples. The vast majority of the Bolivian mtDNAs (98.4%) were found to belong to the main Native American haplogroups (A: 14.3%, B: 52.6%, C: 21.9%, D: 9.6%), with little indication of sub-Saharan and/or European lineages; however, marked patterns of haplogroup frequencies between main regions exist (e.g. haplogroup B: Andean [71%], Sub-Andean [61%], Llanos [32%]). Analysis of entire genomes unraveled the phylogenetic characteristics of three Native haplogroups: the pan-American haplogroup B2b (originated ∼21.4 thousand years ago [kya]), A2ah (∼5.2 kya), and B2o (∼2.6 kya). The data suggest that B2b could have arisen in North California (an origin even in the north most region of the American continent cannot be disregarded), moved southward following the Pacific coastline and crossed Meso-America. Then, it most likely spread into South America following two routes: the Pacific path towards Peru and Bolivia (arriving here at about ∼15.2 kya), and the Amazonian route of Venezuela and Brazil southwards. In contrast to the mtDNA, Ancestry Informative Markers (AIMs) reveal a higher (although geographically variable) European introgression in Bolivians (25%). Bolivia shows a decreasing autosomal molecular diversity pattern along the longitudinal axis, from the Altiplano to the lowlands. Both autosomes and mtDNA revealed a low impact (1–2%) of a sub-Saharan component in Bolivians.     

Plasticity in hydraulic architecture of Scots pine across Eurasia

Widespread tree species must show physiological and structural plasticity to deal with contrasting water balance conditions. To investigate these plasticity mechanisms, a meta-analysis of Pinus sylvestris L. sap flow and its response to environmental variables was conducted using datasets from across its whole geographical range. For each site, a Jarvis-type, multiplicative model was used to fit the relationship between sap flow and photosynthetically active radiation, vapour pressure deficit (D) and soil moisture deficit (SMD); and a logarithmic function was used to characterize the response of stomatal conductance (G _s) to D. The fitted parameters of those models were regressed against climatic variables to study the acclimation of Scots pine to dry/warm conditions. The absolute value of sap flow and its sensitivity to D and SMD increased with the average summer evaporative demand. However, relative sensitivity of G _s to D (m/G _s,ref, where m is the slope and G _s,ref is reference G _s at D = 1 kPa) did not increase with evaporative demand across populations, and transpiration per unit leaf area at a given D increased accordingly in drier/warmer climates. This physiological plasticity was linked to the previously reported climate- and size-related structural acclimation of leaf to sapwood area ratios. G _s,ref, and its absolute sensitivity to D (m), tended to decrease with age/height of the trees as previously reported for other pine species. It is unclear why Scots pines have higher transpiration rates at drier/warmer sites, at the expense of lower water-use efficiency. In any case, our results suggest that these structural adjustments may not be enough to prevent lower xylem tensions at the driest sites.     

Recent evolutionary history of the bluethroat (Luscinia svecica) across Eurasia

We analysed mitochondrial DNA (mtDNA) sequences from 154 bluethroats (Luscinia svecica) sampled at 21 sites throughout much of their Eurasian range. A previously reported, single base-pair mtDNA difference between L. s. svecica and L. s. namnetum was inconsistent upon expanded geographical sampling. A significant FST value (0.29) and an isolation-by-distance effect show the existence of geographical differentiation. Phylogenetic analysis of haplotypes revealed northern and southern groups, although lineage sorting is incomplete. There was no geographical structure to the haplotype tree within groups, and currently recognized subspecies were not supported. A minimum evolution tree based on pairwise mtDNA genetic distances among average samples showed the same two broadly distributed northern and southern groups. These groups abut in the centre of the latitudinal range, and were possibly isolated by forest that developed and spread westward over the last 15 000 years. Pairwise FST values averaged 0.16 in the southern group, 0.04 in the northern group, and 0.42 between groups. Mismatch distributions suggested population growth in each group, with that in the south being more recent. In the northern group, the geographical pattern in tau suggested northward and eastward expansion. Analysis of nucleotide diversity suggested westward expansion in the southern group. The northern group had higher nucleotide diversity than the southern group, consistent with a larger current population size in the north. Given the significant FST, incompletely sorted haplotype tree, and broadly patterned minimum evolution tree, L. svevica appears to represent a species at an intermediate stage of differentiation between panmixia and reciprocal monophyly.     

Distribution of CCR5-delta 32 gene deletion across the Russian part of Eurasia

32-bp inactivating deletion in the β-chemokine receptor 5 (CCR5) gene, common in Nothern European populations, is associated with reduced HIV-1 transmission risk and delayed disease progression. We have studied the deletion distribution in many populations in Eurasia by polymerase chain reaction analysis of 531 DNA samples representing West and East Siberian, Central Asian, and Far Eastern parts of Russia. An unusually high frequency (11.1%) of the deleted variant in natives of West Siberia, of Finno-Ugrian descent, was observed. Furthermore, the deletion was infrequent in indigenous populations of Central Asia, East Siberia, the Russian Far East, and Canada. We conclude that the Δccr5 distribution is limited primarily to Europeans and related western Siberian Finno-Ugrian populations, with a sharp negative gradient toward the east along the territory of Russian Asia. Received: 22 December 1997 / Accepted: 24 March 1998     

Origin and Genetic Diversity of Diploid Parthenogenetic Artemia in Eurasia

There is wide interest in understanding how genetic diversity is generated and maintained in parthenogenetic lineages, as it will help clarify the debate of the evolution and maintenance of sexual reproduction. There are three mechanisms that can be responsible for the generation of genetic diversity of parthenogenetic lineages: contagious parthenogenesis, repeated hybridization and microorganism infections (e.g. Wolbachia). Brine shrimps of the genus Artemia (Crustacea, Branchiopoda, Anostraca) are a good model system to investigate evolutionary transitions between reproductive systems as they include sexual species and lineages of obligate parthenogenetic populations of different ploidy level, which often co-occur. Diploid parthenogenetic lineages produce occasional fully functional rare males, interspecific hybridization is known to occur, but the mechanisms of origin of asexual lineages are not completely understood. Here we sequenced and analysed fragments of one mitochondrial and two nuclear genes from an extensive set of populations of diploid parthenogenetic Artemia and sexual species from Central and East Asia to investigate the evolutionary origin of diploid parthenogenetic Artemia, and geographic origin of the parental taxa. Our results indicate that there are at least two, possibly three independent and recent maternal origins of parthenogenetic lineages, related to A. urmiana and Artemia sp. from Kazakhstan, but that the nuclear genes are very closely related in all the sexual species and parthenogegetic lineages except for A. sinica, who presumable took no part on the origin of diploid parthenogenetic strains. Our data cannot rule out either hybridization between any of the very closely related Asiatic sexual species or rare events of contagious parthenogenesis via rare males as the contributing mechanisms to the generation of genetic diversity in diploid parthenogenetic Artemia lineages.     

Genetic Diversity of Moose (Alces alces L.) in Eurasia

Polymorphism of nucleotide sequence of D-loop fragment of the mitochondrial DNA was studied in 20 moose from several local populations on the territory of Eurasia. Three main haplotype variants of D-loop were detected by molecular phylogenetic method, which formed three clusters named European, Asian, and American. Intraspecies variation in the length of HVSI of D-loop of the mitochondrial DNA of moose was revealed. In the Far Eastern and Yakutian moose, haplotypes with a 75-bp deletion were found, which were most similar with haplotypes (also with the deletion), earlier observed in North American moose [1]. The highest diversity of the haplotypes of mitochondrial DNA is characteristic of Yakutia and the Far East (where three haplotype variants were found), which demonstrates the probable role of the region as the center of the species origin or as the region of ancient population mixture. The geographic region might be considered as a probable source of ancient moose migrations from Asia to America, basing on the data of distribution of mitochondrial haplotypes of D-loop and alleles of MhcAlal-DRB1. Divergence of nucleotide sequences of haplotypes with the 75-bp deletion (forming the American cluster on the phylogenetic tree) was the lowest (0.4%), which evidences respectively recent origin of the group of haplotypes. In Europe, only haplotypes of mitochondrial DNA referred to European variant were observed. Basing on analysis of variation of nucleotide sequences of D-loop, exon 4 of -Casein and exon 2 of MhcAlal-DRB1, we demonstrated that Eurasian moose studied belong to the unique species, which has probably passed through a bottle neck. The time of the origin of modern diversity of D-loop haplotypes of the species was estimated as 0.075–0.15 Myr ago.     

Genetic diversity of moose (Alces alces L.) in Eurasia

Polymorphism of nucleotide sequence of D-loop fragment of the mitochondrial DNA was studied in 20 moose from several local populations on the territory of Eurasia. Three main haplotype variants of D-loop were detected by molecular phylogenetic method, which formed three clusters named European, Asian and American. Intraspecies variation in the length of HVSI of D-loop of the mitochondrial DNA of moose was revealed. In the Far Eastern and Yakutian moose, haplotypes with a 75-bp deletion were found, which were most similar with haplotypes (also with the deletion), earlier observed in North American moose [1]. The highest diversity of the haplotypes of mitochondrial DNA is characteristic of Yakutia and the Far East (where three haplotype variants were found), which demonstrates the probable role of the region as the center of the species or as the region of ancient population mixture. The geographic region might be considered as a probable source of ancient moose migrations from Asia to America, basing on the data of distribution of mitochondrial haplotypes of D-loop and alleles of MhcAlal-DRB1. Divergence of nucleotide sequences of haplotypes with the 75-bp deletion (forming the American cluster on the phylogenetic tree) was the lowest (0.4%), which evidences respectively recent origin of the group of haplotypes. In Europe, only haplotypes of mitochondrial DNA referred to European variant were observed. Basing on analysis of variation of nucleotide sequences of D-loop, exon 4 of kappa-Casein and exon 2 of MhcALal-DRB1, we demonstrated that Eurasian moose studied belong to the unique species, which has probably passed through a bottle neck. The time of the origin of modern diversity of D-loop haplotypes of the species was estimated as 0.075-0.15 Myr ago.     

Objects and Practices of Nomads

Book reviewed in this article:
Bedouins of Qatar . Klaus Ferdinand. The Carlsberg Foundation's Nomad Research Project. New York: Thames and Hudson Ltd., 1993. 400 pp. Nomads of Luristan: History, Material Culture, and Pastoralism in Western Iran . Inge Demant Mortensen. The Carlsberg Foundation's Nomad Research Project. New York: Thames and Hudson Ltd., 1993. 414 pp.     

The theriofaunistic zoning of northern Eurasia

For the purpose of zoning on the basis of theriofauna, Northern Eurasia was considered within the boundaries of the Soviet Union in 1991 and was divided into 245 mapping units. Mapping units were marked on the World Vegetation Map at a scale of 1: 2000000. Each mapping unit occupied a territory within the limits of a natural subzone with a latitudinal distance of 10°. A list of mammal species was generated for each unit. Jaccard similarity coefficients were calculated for these lists; the coefficients were used as the basis for performing cluster analysis of theriofauna of the mapping units. The results of calculations were used to create a hierarchical classification, which includes three theriofauna regions divided into seven subregions. They were classified as island or mainland. All the subregions (except one) were delimited into 18 provinces and 17 districts; one of the districts was delimited into four subdistricts. Environmental factors that correlate with heterogeneity of theriofauna within the studied territory were described. The proposed zoning is 1.9–3 times more informative than previously developed schemes and takes into account 69% of the variance of the similarity coefficients of the faunas of specific regions (coefficient of multiple correlation is 0.83). The association with environmental factors and natural conditions may explain 83% of the heterogeneity of the theriofauna (correlation coefficient is 0.91). Comparing the results of zoning that were carried out for different classes of terrestrial vertebrates, we found significant similarity between causes of fauna heterogeneity (zonal features, remoteness, sun exposure, and their combined effect). In addition, the differences in tolerance to the environment among the studied animal classes resulted in substantial discordance of the boundaries of the described taxa and their hierarchy. This discordance was found during zoning. Because of this, general conclusions concerning the heterogeneity of the fauna of terrestrial vertebrates can be made only after the total analysis of their fauna is completed.     

Genetic Variability of Tick-Borne Encephalitis Virus Genome 5'-UTR from Northern Eurasia

Molecular Biology - This paper reports the analysis of the nucleotide sequences of the 5'-untranslated region (5'-UTR) of tick-borne encephalitis virus (TBEV) genomic RNA isolated from 39...     

The boreal forests of north-eastern Eurasia

The distribution, diversity and structure of boreal forests of monsoon Asia are reviewed. The boreal zone is circumscribed by the isotherms of 15°C and 45°C of Kira's Warmth Index (WI) and includes the territory of the Amur basin, the seashores of the Sea of Okhotsk, Kamchatka, Sakhalin and the Kuril islands. Boreal forests also occur on the mountains of Hokkaido, Honshu, Korea and NE China. The oceanic sectors of the boreal zone are composed mainly of birch forests, the marine sectors of spruce-fir forests and the continental sectors of larch and pine forests. The upper limit of the boreal forests ascends from the lowest level in the North to ca. 1500 m a.s.l. in the South of the zone, and reaches above 2500 m in the mountains of the temperate zone. In the boreal zone the secondary forests are common. They form after fires and cutting. Volcanism is an essential factor in the forest dynamics in the oceanic part of the region. It is suggested that as a result of global warming one may expect a strong alteration in vegetation pattern, especially in the northern and mountain areas.Paper presented at the International Symposium on Global Change Impacts on Terrestrial Ecosystems in Monsoon Asia (TEMA) Waseda University, Tokyo, 4–6 September 1993.     

Genetic and linguistic affinities between human populations in Eurasia and West Africa

This study examines the relationship between genetic distance and linguistic affiliation for five regional sets of populations from Eurasia and West Africa. Human genetic and linguistic diversity have been proposed to be generally correlated, either through a direct link, whereby linguistic and genetic affiliations reflect the same past population processes, or an indirect one, where the evolution of the two types of diversity is independent but conditioned by the same geographical factors. By controlling for proximity, indirect correlations due to common geography are eliminated, and any residual relationships found are likely to reflect common linguistic-genetic processes. Clear relationships between genetic distances and linguistic relatedness are detectable in Europe and East and Central Asia, but not in the Middle East, Southeast Asia, or West Africa. We suggest that linguistic and genetic affiliations will only be correlated under specific conditions, such as where there have been large-scale demic diffusions in the last few thousand years, and relative sedentism in the subsequent period.