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1.
iScience ; 27(6): 110016, 2024 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-38883810

RESUMO

West and South Asian populations profoundly influenced Eurasian genetic and cultural diversity. We investigate the genetic history of the Y chromosome haplogroup L1-M22, which, while prevalent in these regions, lacks in-depth study. Robust Bayesian analyses of 165 high-coverage Y chromosomes favor a West Asian origin for L1-M22 ∼20.6 thousand years ago (kya). Moreover, this haplogroup parallels the genome-wide genetic ancestry of hunter-gatherers from the Iranian Plateau and the Caucasus. We characterized two L1-M22 harboring population groups during the Early Holocene. One expanded with the West Asian Neolithic transition. The other moved to South Asia ∼8-6 kya but showed no expansion. This group likely participated in the spread of Dravidian languages. These South Asian L1-M22 lineages expanded ∼4-3 kya, coinciding with the Steppe ancestry introduction. Our findings advance the current understanding of Eurasian historical dynamics, emphasizing L1-M22's West Asian origin, associated population movements, and possible linguistic impacts.

2.
Mol Biol Evol ; 39(3)2022 03 02.
Artigo em Inglês | MEDLINE | ID: mdl-35294555

RESUMO

Island Southeast Asia (ISEA) and Oceania host one of the world's richest assemblages of human phenotypic, linguistic, and cultural diversity. Despite this, the region's male genetic lineages are globally among the last to remain unresolved. We compiled ∼9.7 Mb of Y chromosome (chrY) sequence from a diverse sample of over 380 men from this region, including 152 first reported here. The granularity of this data set allows us to fully resolve and date the regional chrY phylogeny. This new high-resolution tree confirms two main population bursts: multiple rapid diversifications following the region's initial settlement ∼50 kya, and extensive expansions <6 kya. Notably, ∼40-25 kya the deep rooting local lineages of C-M130, M-P256, and S-B254 show almost no further branching events in ISEA, New Guinea, and Australia, matching a similar pause in diversification seen in maternal mitochondrial DNA lineages. The main local lineages start diversifying ∼25 kya, at the time of the last glacial maximum. This improved chrY topology highlights localized events with important historical implications, including pre-Holocene contact between Mainland and ISEA, potential interactions between Australia and the Papuan world, and a sustained period of diversification following the flooding of the ancient Sunda and Sahul continents as the insular landscape observed today formed. The high-resolution phylogeny of the chrY presented here thus enables a detailed exploration of past isolation, interaction, and change in one of the world's least understood regions.


Assuntos
Povo Asiático , DNA Mitocondrial , Sudeste Asiático , DNA Mitocondrial/genética , Humanos , Masculino , Mitocôndrias/genética , Filogenia
3.
R Soc Open Sci ; 8(12): 202182, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34909208

RESUMO

Integrating datasets from different disciplines is hard because the data are often qualitatively different in meaning, scale and reliability. When two datasets describe the same entities, many scientific questions can be phrased around whether the (dis)similarities between entities are conserved across such different data. Our method, CLARITY, quantifies consistency across datasets, identifies where inconsistencies arise and aids in their interpretation. We illustrate this using three diverse comparisons: gene methylation versus expression, evolution of language sounds versus word use, and country-level economic metrics versus cultural beliefs. The non-parametric approach is robust to noise and differences in scaling, and makes only weak assumptions about how the data were generated. It operates by decomposing similarities into two components: a 'structural' component analogous to a clustering, and an underlying 'relationship' between those structures. This allows a 'structural comparison' between two similarity matrices using their predictability from 'structure'. Significance is assessed with the help of re-sampling appropriate for each dataset. The software, CLARITY, is available as an R package from github.com/danjlawson/CLARITY.

4.
Curr Biol ; 31(19): 4219-4230.e10, 2021 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-34388371

RESUMO

Multiple lines of evidence show that modern humans interbred with archaic Denisovans. Here, we report an account of shared demographic history between Australasians and Denisovans distinctively in Island Southeast Asia. Our analyses are based on ∼2.3 million genotypes from 118 ethnic groups of the Philippines, including 25 diverse self-identified Negrito populations, along with high-coverage genomes of Australopapuans and Ayta Magbukon Negritos. We show that Ayta Magbukon possess the highest level of Denisovan ancestry in the world-∼30%-40% greater than that of Australians and Papuans-consistent with an independent admixture event into Negritos from Denisovans. Together with the recently described Homo luzonensis, we suggest that there were multiple archaic species that inhabited the Philippines prior to the arrival of modern humans and that these archaic groups may have been genetically related. Altogether, our findings unveil a complex intertwined history of modern and archaic humans in the Asia-Pacific region, where distinct Islander Denisovan populations differentially admixed with incoming Australasians across multiple locations and at various points in time.


Assuntos
Hominidae , Homem de Neandertal , Animais , Ásia , Sudeste Asiático , Austrália , Hominidae/genética , Humanos , Homem de Neandertal/genética , Filipinas , Grupos Raciais
5.
Proc Natl Acad Sci U S A ; 118(13)2021 03 30.
Artigo em Inglês | MEDLINE | ID: mdl-33753512

RESUMO

Island Southeast Asia has recently produced several surprises regarding human history, but the region's complex demography remains poorly understood. Here, we report ∼2.3 million genotypes from 1,028 individuals representing 115 indigenous Philippine populations and genome-sequence data from two ∼8,000-y-old individuals from Liangdao in the Taiwan Strait. We show that the Philippine islands were populated by at least five waves of human migration: initially by Northern and Southern Negritos (distantly related to Australian and Papuan groups), followed by Manobo, Sama, Papuan, and Cordilleran-related populations. The ancestors of Cordillerans diverged from indigenous peoples of Taiwan at least ∼8,000 y ago, prior to the arrival of paddy field rice agriculture in the Philippines ∼2,500 y ago, where some of their descendants remain to be the least admixed East Asian groups carrying an ancestry shared by all Austronesian-speaking populations. These observations contradict an exclusive "out-of-Taiwan" model of farming-language-people dispersal within the last four millennia for the Philippines and Island Southeast Asia. Sama-related ethnic groups of southwestern Philippines additionally experienced some minimal South Asian gene flow starting ∼1,000 y ago. Lastly, only a few lowlanders, accounting for <1% of all individuals, presented a low level of West Eurasian admixture, indicating a limited genetic legacy of Spanish colonization in the Philippines. Altogether, our findings reveal a multilayered history of the Philippines, which served as a crucial gateway for the movement of people that ultimately changed the genetic landscape of the Asia-Pacific region.


Assuntos
Migração Humana/história , Grupos Populacionais/história , Agricultura , Sudeste Asiático/etnologia , Austrália/etnologia , Feminino , Deriva Genética , Genômica , História Antiga , Humanos , Masculino , Oryza , Filipinas , Grupos Populacionais/genética , Taiwan/etnologia
6.
Eur J Hum Genet ; 27(9): 1466-1474, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-30976109

RESUMO

Kalmyks, the only Mongolic-speaking population in Europe, live in the southeast of the European Plain, in Russia. They adhere to Buddhism and speak a dialect of the Mongolian language. Historical and linguistic evidence, as well a shared clan names, suggests a common origin with Oirats of western Mongolia; yet, only a limited number of genetic studies have focused on this topic. Here we compare the paternal genetic relationship of Kalmyk clans with ethnographically related groups from Mongolia, Kyrgyzstan and China, within the context of their neighbouring populations. A phylogeny of 37 high-coverage Y-chromosome sequences, together with further genotyping of larger sample sets, reveals that all the Oirat-speaking populations studied here, including Kalmyks, share, as a dominant paternal lineage, Y-chromosomal haplogroup C3c1-M77, which is also present in several geographically distant native Siberian populations. We identify a subset of this clade, C3c1b-F6379, specifically enriched in Kalmyks as well as in Oirat-speaking clans in Inner Asia. This sub-clade coalesces at around 1500 years before present, before the Genghis Khan era, and significantly earlier than the split between Kalmyks and other Oirat speakers about 400 years ago. We also show that split between the dominant hg C variant among Buryats-C3-M407-and that of C3-F6379, took place in the Early Upper Palaeolithic, suggesting an extremely long duration for the dissipation of hg C3-M217 carriers across northern Eurasia, which cuts through today's major linguistic phyla.


Assuntos
Povo Asiático/genética , Cromossomos Humanos Y , Genética Populacional , Mapeamento Cromossômico , Europa (Continente) , Genótipo , Geografia , Haplótipos , Humanos , Masculino , Repetições de Microssatélites , Mongólia , Filogenia , Polimorfismo Genético , Polimorfismo de Nucleotídeo Único
7.
Science ; 360(6392): 1024-1027, 2018 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-29853687

RESUMO

Little is known regarding the first people to enter the Americas and their genetic legacy. Genomic analysis of the oldest human remains from the Americas showed a direct relationship between a Clovis-related ancestral population and all modern Central and South Americans as well as a deep split separating them from North Americans in Canada. We present 91 ancient human genomes from California and Southwestern Ontario and demonstrate the existence of two distinct ancestries in North America, which possibly split south of the ice sheets. A contribution from both of these ancestral populations is found in all modern Central and South Americans. The proportions of these two ancestries in ancient and modern populations are consistent with a coastal dispersal and multiple admixture events.


Assuntos
Evolução Biológica , Emigração e Imigração , Genoma Humano , População/genética , California , Humanos , Ontário
8.
Sci Rep ; 8(1): 1823, 2018 01 29.
Artigo em Inglês | MEDLINE | ID: mdl-29379068

RESUMO

The debate concerning the origin of the Polynesian speaking peoples has been recently reinvigorated by genetic evidence for secondary migrations to western Polynesia from the New Guinea region during the 2nd millennium BP. Using genome-wide autosomal data from the Leeward Society Islands, the ancient cultural hub of eastern Polynesia, we find that the inhabitants' genomes also demonstrate evidence of this episode of admixture, dating to 1,700-1,200 BP. This supports a late settlement chronology for eastern Polynesia, commencing ~1,000 BP, after the internal differentiation of Polynesian society. More than 70% of the autosomal ancestry of Leeward Society Islanders derives from Island Southeast Asia with the lowland populations of the Philippines as the single largest potential source. These long-distance migrants into Polynesia experienced additional admixture with northern Melanesians prior to the secondary migrations of the 2nd millennium BP. Moreover, the genetic diversity of mtDNA and Y chromosome lineages in the Leeward Society Islands is consistent with linguistic evidence for settlement of eastern Polynesia proceeding from the central northern Polynesian outliers in the Solomon Islands. These results stress the complex demographic history of the Leeward Society Islands and challenge phylogenetic models of cultural evolution predicated on eastern Polynesia being settled from Samoa.


Assuntos
Cromossomos Humanos Y/genética , Variação Genética/genética , Genoma/genética , DNA Mitocondrial/genética , Emigração e Imigração , Genética Populacional/métodos , Haplótipos/genética , Humanos , Masculino , Nova Guiné , Filipinas , Filogenia , Polinésia
9.
Sci Rep ; 6: 30197, 2016 07 25.
Artigo em Inglês | MEDLINE | ID: mdl-27453128

RESUMO

Medieval era encounters of nomadic groups of the Eurasian Steppe and largely sedentary East Europeans had a variety of demographic and cultural consequences. Amongst these outcomes was the emergence of the Lipka Tatars-a Slavic-speaking Sunni-Muslim minority residing in modern Belarus, Lithuania and Poland, whose ancestors arrived in these territories via several migration waves, mainly from the Golden Horde. Our results show that Belarusian Lipka Tatars share a substantial part of their gene pool with Europeans as indicated by their Y-chromosomal, mitochondrial and autosomal DNA variation. Nevertheless, Belarusian Lipkas still retain a strong genetic signal of their nomadic ancestry, witnessed by the presence of common Y-chromosomal and mitochondrial DNA variants as well as autosomal segments identical by descent between Lipkas and East Eurasians from temperate and northern regions. Hence, we document Lipka Tatars as a unique example of former Medieval migrants into Central Europe, who became sedentary, changed language to Slavic, yet preserved their faith and retained, both uni- and bi-parentally, a clear genetic echo of a complex population interplay throughout the Eurasian Steppe Belt, extending from Central Europe to northern China.


Assuntos
Etnicidade/genética , Variação Genética/genética , População Branca/genética , China , Cromossomos Humanos Y/genética , DNA Mitocondrial/genética , Europa (Continente) , Genética Populacional/métodos , Humanos , Filogenia , Polônia , Migrantes
10.
Proc Natl Acad Sci U S A ; 113(25): 6892-7, 2016 06 21.
Artigo em Inglês | MEDLINE | ID: mdl-27274055

RESUMO

The publication in 2001 by Adcock et al. [Adcock GJ, et al. (2001) Proc Natl Acad Sci USA 98(2):537-542] in PNAS reported the recovery of short mtDNA sequences from ancient Australians, including the 42,000-y-old Mungo Man [Willandra Lakes Hominid (WLH3)]. This landmark study in human ancient DNA suggested that an early modern human mitochondrial lineage emerged in Asia and that the theory of modern human origins could no longer be considered solely through the lens of the "Out of Africa" model. To evaluate these claims, we used second generation DNA sequencing and capture methods as well as PCR-based and single-primer extension (SPEX) approaches to reexamine the same four Willandra Lakes and Kow Swamp 8 (KS8) remains studied in the work by Adcock et al. Two of the remains sampled contained no identifiable human DNA (WLH15 and WLH55), whereas the Mungo Man (WLH3) sample contained no Aboriginal Australian DNA. KS8 reveals human mitochondrial sequences that differ from the previously inferred sequence. Instead, we recover a total of five modern European contaminants from Mungo Man (WLH3). We show that the remaining sample (WLH4) contains ∼1.4% human DNA, from which we assembled two complete mitochondrial genomes. One of these was a previously unidentified Aboriginal Australian haplotype belonging to haplogroup S2 that we sequenced to a high coverage. The other was a contaminating modern European mitochondrial haplotype. Although none of the sequences that we recovered matched those reported by Adcock et al., except a contaminant, these findings show the feasibility of obtaining important information from ancient Aboriginal Australian remains.


Assuntos
DNA Mitocondrial/genética , Austrália , Humanos , Funções Verossimilhança , Filogenia
11.
PLoS One ; 10(9): e0135820, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26332464

RESUMO

The Slavic branch of the Balto-Slavic sub-family of Indo-European languages underwent rapid divergence as a result of the spatial expansion of its speakers from Central-East Europe, in early medieval times. This expansion-mainly to East Europe and the northern Balkans-resulted in the incorporation of genetic components from numerous autochthonous populations into the Slavic gene pools. Here, we characterize genetic variation in all extant ethnic groups speaking Balto-Slavic languages by analyzing mitochondrial DNA (n = 6,876), Y-chromosomes (n = 6,079) and genome-wide SNP profiles (n = 296), within the context of other European populations. We also reassess the phylogeny of Slavic languages within the Balto-Slavic branch of Indo-European. We find that genetic distances among Balto-Slavic populations, based on autosomal and Y-chromosomal loci, show a high correlation (0.9) both with each other and with geography, but a slightly lower correlation (0.7) with mitochondrial DNA and linguistic affiliation. The data suggest that genetic diversity of the present-day Slavs was predominantly shaped in situ, and we detect two different substrata: 'central-east European' for West and East Slavs, and 'south-east European' for South Slavs. A pattern of distribution of segments identical by descent between groups of East-West and South Slavs suggests shared ancestry or a modest gene flow between those two groups, which might derive from the historic spread of Slavic people.


Assuntos
Cromossomos Humanos Y/genética , DNA Mitocondrial/genética , Pool Gênico , Variação Genética , Idioma , População Branca/genética , Europa (Continente) , Humanos , Filogenia , Polimorfismo de Nucleotídeo Único
12.
BMC Evol Biol ; 14: 109, 2014 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-24885141

RESUMO

BACKGROUND: Complete mitochondrial DNA (mtDNA) genome analyses have greatly improved the phylogeny and phylogeography of human mtDNA. Human mitochondrial DNA haplogroup U6 has been considered as a molecular signal of a Paleolithic return to North Africa of modern humans from southwestern Asia. RESULTS: Using 230 complete sequences we have refined the U6 phylogeny, and improved the phylogeographic information by the analysis of 761 partial sequences. This approach provides chronological limits for its arrival to Africa, followed by its spreads there according to climatic fluctuations, and its secondary prehistoric and historic migrations out of Africa colonizing Europe, the Canary Islands and the American Continent. CONCLUSIONS: The U6 expansions and contractions inside Africa faithfully reflect the climatic fluctuations that occurred in this Continent affecting also the Canary Islands. Mediterranean contacts drove these lineages to Europe, at least since the Neolithic. In turn, the European colonization brought different U6 lineages throughout the American Continent leaving the specific sign of the colonizers origin.


Assuntos
DNA Mitocondrial/genética , Fluxo Gênico , Migração Humana , Filogeografia , Análise de Sequência de DNA , África , Ásia , Europa (Continente) , Genética Populacional , Haplótipos , Humanos , Dados de Sequência Molecular , Filogenia
13.
Eur J Hum Genet ; 22(12): 1404-12, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24667789

RESUMO

The northern region of the Indian subcontinent is a vast landscape interlaced by diverse ecologies, for example, the Gangetic Plain and the Himalayas. A great number of ethnic groups are found there, displaying a multitude of languages and cultures. The Tharu is one of the largest and most linguistically diverse of such groups, scattered across the Tarai region of Nepal and bordering Indian states. Their origins are uncertain. Hypotheses have been advanced postulating shared ancestry with Austroasiatic, or Tibeto-Burman-speaking populations as well as aboriginal roots in the Tarai. Several Tharu groups speak a variety of Indo-Aryan languages, but have traditionally been described by ethnographers as representing East Asian phenotype. Their ancestry and intra-population diversity has previously been tested only for haploid (mitochondrial DNA and Y-chromosome) markers in a small portion of the population. This study presents the first systematic genetic survey of the Tharu from both Nepal and two Indian states of Uttarakhand and Uttar Pradesh, using genome-wide SNPs and haploid markers. We show that the Tharu have dual genetic ancestry as up to one-half of their gene pool is of East Asian origin. Within the South Asian proportion of the Tharu genetic ancestry, we see vestiges of their common origin in the north of the South Asian Subcontinent manifested by mitochondrial DNA haplogroup M43.


Assuntos
Povo Asiático/genética , Etnicidade/genética , Cromossomos Humanos Y/genética , DNA Mitocondrial/genética , Estudos de Associação Genética , Variação Genética , Técnicas de Genotipagem , Haplótipos , Humanos , Índia , Nepal , Filogeografia , Polimorfismo de Nucleotídeo Único , Análise de Sequência de DNA
14.
Hum Biol ; 85(1-3): 7-20, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24297218

RESUMO

The "negrito" hypothesis predicts that a shared phenotype among various contemporary groups of hunter-gatherers in Southeast Asia--dark skin, short stature, tight curly hair--is due to common descent from a region-wide, pre-Neolithic substrate of humanity. The alternative is that their distinctive phenotype results from convergent evolution. The core issues of the negrito hypothesis are today more relevant than ever to studies of human evolution, including the out-of-Africa migration, admixture with Denisovans, and the effects of environment and ecology on life-history traits. Understanding the current distribution of the negrito phenotype dictates a wide-ranging remit for study, including the articulation of the relationship between foragers and farmers in the present, the development of settled agriculture in the mid-Holocene, and terminal Pleistocene population expansions. The consensus reached by the contributors to this special double issue of Human Biology is that there is not yet conclusive evidence either for or against the negrito hypothesis. Nevertheless, the process of revisiting the problem will benefit the knowledge of the human prehistory of Southeast Asia. Whether the term negrito accurately reflects the all-encompassing nature of the resulting inquiry is in itself questionable, but the publication of this double issue is testament to the enduring ability of this hypothesis to unite disparate academic disciplines in a common purpose.


Assuntos
Antropologia Física , Povo Asiático/genética , Evolução Biológica , Variação Genética , Genética Populacional , Hominidae/genética , Animais , Comportamento Apetitivo , Sudeste Asiático , Povo Asiático/etnologia , Marcadores Genéticos , Humanos , Fenótipo , Dinâmica Populacional
15.
Hum Biol ; 85(1-3): 153-72, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24297224

RESUMO

The indigenous inhabitants of the Andaman Islands were considered by many early anthropologists to be pristine examples of a "negrito" substrate of humanity that existed throughout Southeast Asia. Despite over 150 years of research and study, questions over the extent of shared ancestry between Andaman Islanders and other small-bodied, gracile, dark-skinned populations throughout the region are still unresolved. This shared phenotype could be a product of shared history, evolutionary convergence, or a mixture of both. Recent population genetic studies have tended to emphasize long-term physical isolation of the Andaman Islanders and an affinity to ancestral populations of South Asia. We reexamine the genetic evidence from genome-wide autosomal single-nucleotide polymorphism (SNP) data for a shared history between the tribes of Little Andaman (Onge) and Great Andaman, and between these two groups and the rest of South and Southeast Asia (both negrito and non-negrito groups).


Assuntos
Povo Asiático/genética , Genética Populacional , Arqueologia , Sudeste Asiático/etnologia , Povo Asiático/etnologia , Evolução Biológica , DNA Mitocondrial/genética , Emigração e Imigração , Variação Genética , Genótipo , Humanos , Fenótipo , Filogenia , Polimorfismo de Nucleotídeo Único
16.
J Hum Evol ; 59(1): 87-95, 2010 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-20510437

RESUMO

A better understanding of the evolutionary relationship between modern humans and Neanderthals is essential for improving the resolution of hominin phylogenetic hypotheses. Currently, four distinct chronologies for the timing of population divergence are available, ranging from the late Middle Pleistocene to the late Early Pleistocene, each based on different interpretations of hominin taxonomy. Genetic data can present an independent estimate of the evolutionary timescale involved, making it possible to distinguish between these competing models of hominin evolution. We analysed five dated Neanderthal mitochondrial genomes, together with those of 54 modern humans, and inferred a genetic chronology using multiple age calibrations. Our mean date estimates are consistent with a process of genetic divergence within an ancestral population, commencing approximately 410-440 ka. These results suggest that a reappraisal of key elements in the Pleistocene hominin fossil record may now be required.


Assuntos
DNA Mitocondrial/genética , Genoma Humano , Hominidae/genética , Modelos Genéticos , Animais , Antropologia Física , Teorema de Bayes , Evolução Molecular , Fósseis , Humanos , Filogenia , Alinhamento de Sequência
17.
Nucleic Acids Res ; 38(2): e7, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19864251

RESUMO

The analysis of targeted genetic loci from ancient, forensic and clinical samples is usually built upon polymerase chain reaction (PCR)-generated sequence data. However, many studies have shown that PCR amplification from poor-quality DNA templates can create sequence artefacts at significant levels. With hominin (human and other hominid) samples, the pervasive presence of highly PCR-amplifiable human DNA contaminants in the vast majority of samples can lead to the creation of recombinant hybrids and other non-authentic artefacts. The resulting PCR-generated sequences can then be difficult, if not impossible, to authenticate. In contrast, single primer extension (SPEX)-based approaches can genotype single nucleotide polymorphisms from ancient fragments of DNA as accurately as modern DNA. A single SPEX-type assay can amplify just one of the duplex DNA strands at target loci and generate a multi-fold depth-of-coverage, with non-authentic recombinant hybrids reduced to undetectable levels. Crucially, SPEX-type approaches can preferentially access genetic information from damaged and degraded endogenous ancient DNA templates over modern human DNA contaminants. The development of SPEX-type assays offers the potential for highly accurate, quantitative genotyping from ancient hominin samples.


Assuntos
Hominidae/genética , Técnicas de Amplificação de Ácido Nucleico/métodos , Polimorfismo de Nucleotídeo Único , Análise de Sequência de DNA , Animais , Sequência de Bases , Genótipo , Humanos , Dados de Sequência Molecular , Museus , Reação em Cadeia da Polimerase , Reprodutibilidade dos Testes
18.
Trends Ecol Evol ; 24(9): 515-21, 2009 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-19682765

RESUMO

Different methodologies and modes of calibration have produced disparate, sometimes irreconcilable, reconstructions of the evolutionary and demographic history of our species. We discuss how date estimates are affected by the choice of molecular data and methodology, and evaluate various mitochondrial estimates of the timescale of human evolution in the context of the contemporary palaeontological and archaeological evidence for key stages in human prehistory. We contend that some of the most widely-cited mitochondrial rate estimates have several significant shortcomings, including a reliance on a human-chimpanzee calibration, and highlight the pressing need for revised rate estimates.


Assuntos
Evolução Biológica , Mitocôndrias/genética , DNA Mitocondrial/química , Evolução Molecular , Fósseis , Genoma Mitocondrial , Humanos , Filogenia , Fatores de Tempo
19.
BMC Genet ; 10: 29, 2009 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-19545382

RESUMO

BACKGROUND: Progress in the field of human ancient DNA studies has been severely restricted due to the myriad sources of potential contamination, and because of the pronounced difficulty in identifying authentic results. Improving the robustness of human aDNA results is a necessary pre-requisite to vigorously testing hypotheses about human evolution in Europe, including possible admixture with Neanderthals. This study approaches the problem of distinguishing between authentic and contaminating sequences from common European mtDNA haplogroups by applying a multiplexed Single-Base-Extension assay, containing both control and coding region sites, to DNA extracted from the Tyrolean Iceman. RESULTS: The multiplex assay developed for this study was able to confirm that the Iceman's mtDNA belongs to a new European mtDNA clade with a very limited distribution amongst modern data sets. Controlled contamination experiments show that the correct results are returned by the multiplex assay even in the presence of substantial amounts of exogenous DNA. The overall level of discrimination achieved by targeting both control and coding region polymorphisms in a single reaction provides a methodology capable of dealing with most cases of homoplasy prevalent in European haplogroups. CONCLUSION: The new genotyping results for the Iceman confirm the extreme fallibility of human aDNA studies in general, even when authenticated by independent replication. The sensitivity and accuracy of the multiplex Single-Base-Extension methodology forms part of an emerging suite of alternative techniques for the accurate retrieval of ancient DNA sequences from both anatomically modern humans and Neanderthals. The contamination of laboratories remains a pressing concern in aDNA studies, both in the pre and post-PCR environments, and the adoption of a forensic style assessment of a priori risks would significantly improve the credibility of results.


Assuntos
Evolução Biológica , DNA Mitocondrial/genética , Reação em Cadeia da Polimerase/métodos , Polimorfismo Genético , Osso e Ossos/química , Evolução Molecular , Humanos , Sensibilidade e Especificidade , Análise de Sequência de DNA/métodos
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