Publications by authors named "Bastien Llamas"

69 Publications

Ethics of DNA research on human remains: five globally applicable guidelines.

Nature 2021 Nov 20;599(7883):41-46. Epub 2021 Oct 20.

Department of Genetics, Harvard Medical School, Boston, MA, USA.

We are a group of archaeologists, anthropologists, curators and geneticists representing diverse global communities and 31 countries. All of us met in a virtual workshop dedicated to ethics in ancient DNA research held in November 2020. There was widespread agreement that globally applicable ethical guidelines are needed, but that recent recommendations grounded in discussion about research on human remains from North America are not always generalizable worldwide. Here we propose the following globally applicable guidelines, taking into consideration diverse contexts. These hold that: (1) researchers must ensure that all regulations were followed in the places where they work and from which the human remains derived; (2) researchers must prepare a detailed plan prior to beginning any study; (3) researchers must minimize damage to human remains; (4) researchers must ensure that data are made available following publication to allow critical re-examination of scientific findings; and (5) researchers must engage with other stakeholders from the beginning of a study and ensure respect and sensitivity to stakeholder perspectives. We commit to adhering to these guidelines and expect they will promote a high ethical standard in DNA research on human remains going forward.
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http://dx.doi.org/10.1038/s41586-021-04008-xDOI Listing
November 2021

Mitogenomes Reveal Two Major Influxes of Papuan Ancestry across Wallacea Following the Last Glacial Maximum and Austronesian Contact.

Genes (Basel) 2021 06 24;12(7). Epub 2021 Jun 24.

Australian Centre for Ancient DNA, School of Biological Sciences, University of Adelaide, Adelaide 5005, Australia.

The tropical archipelago of Wallacea contains thousands of individual islands interspersed between mainland Asia and Near Oceania, and marks the location of a series of ancient oceanic voyages leading to the peopling of Sahul-i.e., the former continent that joined Australia and New Guinea at a time of lowered sea level-by 50,000 years ago. Despite the apparent deep antiquity of human presence in Wallacea, prior population history research in this region has been hampered by patchy archaeological and genetic records and is largely concentrated upon more recent history that follows the arrival of Austronesian seafarers ~3000-4000 years ago (3-4 ka). To shed light on the deeper history of Wallacea and its connections with New Guinea and Australia, we performed phylogeographic analyses on 656 whole mitogenomes from these three regions, including 186 new samples from eight Wallacean islands and three West Papuan populations. Our results point to a surprisingly dynamic population history in Wallacea, marked by two periods of extensive demographic change concentrated around the Last Glacial Maximum ~15 ka and post-Austronesian contact ~3 ka. These changes appear to have greatly diminished genetic signals informative about the original peopling of Sahul, and have important implications for our current understanding of the population history of the region.
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http://dx.doi.org/10.3390/genes12070965DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8306604PMC
June 2021

Ancient mitochondrial genomes from the Argentinian Pampas inform the early peopling of the Southern Cone of South America.

iScience 2021 Jun 19;24(6):102553. Epub 2021 May 19.

UCSC Paleogenomics Department of Anthropology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA.

The Southern Cone of South America (SCSA) is a key region for investigations about the peopling of the Americas. However, little is known about the eastern sector, the Argentinian Pampas. We analyzed 18 mitochondrial genomes-7 of which are novel-from human skeletal remains from 3 Early to Late Holocene archaeological sites. The Pampas present a distinctive genetic makeup compared to other Middle to Late Holocene pre-Columbian SCSA populations. We also report the earliest individuals carrying SCSA-specific mitochondrial haplogroups D1j and D1g from Early and Middle Holocene, respectively. Using these deep calibration time points in Bayesian phylogenetic reconstructions, we suggest that the first settlers of the Pampas were part of a single and rapid dispersal ∼15,600 years ago. Finally, we propose that present-day genetic differences between the Pampas and the rest of the SCSA are due to founder effects, genetic drift, and a partial population replacement ∼9,000 years ago.
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http://dx.doi.org/10.1016/j.isci.2021.102553DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8188552PMC
June 2021

Stochastic models support rapid peopling of Late Pleistocene Sahul.

Nat Commun 2021 04 29;12(1):2440. Epub 2021 Apr 29.

Global Ecology, College of Science and Engineering, Flinders University, Adelaide, SA, Australia.

The peopling of Sahul (the combined continent of Australia and New Guinea) represents the earliest continental migration and settlement event of solely anatomically modern humans, but its patterns and ecological drivers remain largely conceptual in the current literature. We present an advanced stochastic-ecological model to test the relative support for scenarios describing where and when the first humans entered Sahul, and their most probable routes of early settlement. The model supports a dominant entry via the northwest Sahul Shelf first, potentially followed by a second entry through New Guinea, with initial entry most consistent with 50,000 or 75,000 years ago based on comparison with bias-corrected archaeological map layers. The model's emergent properties predict that peopling of the entire continent occurred rapidly across all ecological environments within 156-208 human generations (4368-5599 years) and at a plausible rate of 0.71-0.92 km year. More broadly, our methods and approaches can readily inform other global migration debates, with results supporting an exit of anatomically modern humans from Africa 63,000-90,000 years ago, and the peopling of Eurasia in as little as 12,000-15,000 years via inland routes.
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http://dx.doi.org/10.1038/s41467-021-21551-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8085232PMC
April 2021

Systematic benchmark of ancient DNA read mapping.

Brief Bioinform 2021 09;22(5)

Australian Centre for Ancient DNA, School of Biological Sciences, The University of Adelaide, South Australia, 5005, Australia.

The current standard practice for assembling individual genomes involves mapping millions of short DNA sequences (also known as DNA 'reads') against a pre-constructed reference genome. Mapping vast amounts of short reads in a timely manner is a computationally challenging task that inevitably produces artefacts, including biases against alleles not found in the reference genome. This reference bias and other mapping artefacts are expected to be exacerbated in ancient DNA (aDNA) studies, which rely on the analysis of low quantities of damaged and very short DNA fragments (~30-80 bp). Nevertheless, the current gold-standard mapping strategies for aDNA studies have effectively remained unchanged for nearly a decade, during which time new software has emerged. In this study, we used simulated aDNA reads from three different human populations to benchmark the performance of 30 distinct mapping strategies implemented across four different read mapping software-BWA-aln, BWA-mem, NovoAlign and Bowtie2-and quantified the impact of reference bias in downstream population genetic analyses. We show that specific NovoAlign, BWA-aln and BWA-mem parameterizations achieve high mapping precision with low levels of reference bias, particularly after filtering out reads with low mapping qualities. However, unbiased NovoAlign results required the use of an IUPAC reference genome. While relevant only to aDNA projects where reference population data are available, the benefit of using an IUPAC reference demonstrates the value of incorporating population genetic information into the aDNA mapping process, echoing recent results based on graph genome representations.
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http://dx.doi.org/10.1093/bib/bbab076DOI Listing
September 2021

Genozip - A Universal Extensible Genomic Data Compressor.

Bioinformatics 2021 Feb 15. Epub 2021 Feb 15.

Australian Centre for Ancient DNA, School of Biological Sciences, Faculty of Sciences, The University of Adelaide, Adelaide SA 5005, Australia.

We present Genozip, a universal and fully featured compression software for genomic data. Genozip is designed to be a general-purpose software and a development framework for genomic compression by providing five core capabilities - universality (support for all common genomic file formats), high compression ratios, speed, feature-richness, and extensibility. Genozip delivers high-performance compression for widely-used genomic data formats in genomics research, namely FASTQ, SAM/BAM/CRAM, VCF, GVF, FASTA, PHYLIP, and 23andMe formats. Our test results show that Genozip is fast and achieves greatly improved compression ratios, even when the files are already compressed. Further, Genozip is architected with a separation of the Genozip Framework from file-format-specific Segmenters and data-type-specific Codecs. With this, we intend for Genozip to be a general-purpose compression platform where researchers can implement compression for additional file formats, as well as new codecs for data types or fields within files, in the future. We anticipate that this will ultimately increase the visibility and adoption of these algorithms by the user community, thereby accelerating further innovation in this space. Availability: Genozip is written in C. The code is open-source and available on GitHub (https://github.com/divonlan/genozip). The package is free for non-commercial use. It is distributed as a Docker container on DockerHub and through the conda package manager. Genozip is tested on Linux, Mac, and Windows. Supplementary information: Supplementary data are available at Bioinformatics online.
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http://dx.doi.org/10.1093/bioinformatics/btab102DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8388020PMC
February 2021

A Multidisciplinary Review of the Inka Imperial Resettlement Policy and Implications for Future Investigations.

Genes (Basel) 2021 02 2;12(2). Epub 2021 Feb 2.

Australian Centre for Ancient DNA, School of Biological Sciences and The Environment Institute, Adelaide University, Adelaide, SA 5005, Australia.

The rulers of the Inka empire conquered approximately 2 million km of the South American Andes in just under 100 years from 1438-1533 CE. Inside the empire, the elite conducted a systematic resettlement of the many Indigenous peoples in the Andes that had been rapidly colonised. The nature of this resettlement phenomenon is recorded within the Spanish colonial ethnohistorical record. Here we have broadly characterised the resettlement policy, despite the often incomplete and conflicting details in the descriptions. We then review research from multiple disciplines that investigate the empirical reality of the Inka resettlement policy, including stable isotope analysis, intentional cranial deformation morphology, ceramic artefact chemical analyses and genetics. Further, we discuss the benefits and limitations of each discipline for investigating the resettlement policy and emphasise their collective value in an interdisciplinary characterisation of the resettlement policy.
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http://dx.doi.org/10.3390/genes12020215DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7913103PMC
February 2021

Ancient DNA Studies in Pre-Columbian Mesoamerica.

Genes (Basel) 2020 11 13;11(11). Epub 2020 Nov 13.

Australian Centre for Ancient DNA, School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia.

Mesoamerica is a historically and culturally defined geographic area comprising current central and south Mexico, Belize, Guatemala, El Salvador, and border regions of Honduras, western Nicaragua, and northwestern Costa Rica. The permanent settling of Mesoamerica was accompanied by the development of agriculture and pottery manufacturing (2500 BCE-150 CE), which led to the rise of several cultures connected by commerce and farming. Hence, Mesoamericans probably carried an invaluable genetic diversity partly lost during the Spanish conquest and the subsequent colonial period. Mesoamerican ancient DNA (aDNA) research has mainly focused on the study of mitochondrial DNA in the Basin of Mexico and the Yucatán Peninsula and its nearby territories, particularly during the Postclassic period (900-1519 CE). Despite limitations associated with the poor preservation of samples in tropical areas, recent methodological improvements pave the way for a deeper analysis of Mesoamerica. Here, we review how aDNA research has helped discern population dynamics patterns in the pre-Columbian Mesoamerican context, how it supports archaeological, linguistic, and anthropological conclusions, and finally, how it offers new working hypotheses.
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http://dx.doi.org/10.3390/genes11111346DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7696771PMC
November 2020

Equitable Expanded Carrier Screening Needs Indigenous Clinical and Population Genomic Data.

Am J Hum Genet 2020 08;107(2):175-182

National Centre for Indigenous Genomics, Australian National University, Canberra, ACT 2600, Australia; John Curtin School of Medical Research, Australian National University, Canberra, ACT 2600, Australia.

Expanded carrier screening (ECS) for recessive monogenic diseases requires prior knowledge of genomic variation, including DNA variants that cause disease. The composition of pathogenic variants differs greatly among human populations, but historically, research about monogenic diseases has focused mainly on people with European ancestry. By comparison, less is known about pathogenic DNA variants in people from other parts of the world. Consequently, inclusion of currently underrepresented Indigenous and other minority population groups in genomic research is essential to enable equitable outcomes in ECS and other areas of genomic medicine. Here, we discuss this issue in relation to the implementation of ECS in Australia, which is currently being evaluated as part of the national Government's Genomics Health Futures Mission. We argue that significant effort is required to build an evidence base and genomic reference data so that ECS can bring significant clinical benefit for many Aboriginal and/or Torres Strait Islander Australians. These efforts are essential steps to achieving the Australian Government's objectives and its commitment "to leveraging the benefits of genomics in the health system for all Australians." They require culturally safe, community-led research and community involvement embedded within national health and medical genomics programs to ensure that new knowledge is integrated into medicine and health services in ways that address the specific and articulated cultural and health needs of Indigenous people. Until this occurs, people who do not have European ancestry are at risk of being, in relative terms, further disadvantaged.
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http://dx.doi.org/10.1016/j.ajhg.2020.06.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7413856PMC
August 2020

Ancient DNA of northern China Hystricidae sub-fossils reveals the evolutionary history of old world porcupines in the Late Pleistocene.

BMC Evol Biol 2020 07 18;20(1):88. Epub 2020 Jul 18.

State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, 430078, China.

Background: Old World porcupines (Family: Hystricidae) are the third-largest rodents and inhabit southern Europe, Asia, and most regions of Africa. They are a typical indicator of warm climate and their distribution is restricted to tropical and subtropical zones. In China, porcupines are widely distributed in southern areas of the Yangtze River. However, fossil remains have been identified in a few sites in northern China, among which Tianyuan Cave-near Zhoukoudian site-represents the latest known porcupine fossil record. So far, studies have focused mainly on porcupines' husbandry and domestication but little is known about their intrafamilial phylogenetic relationships and evolutionary history.

Results: In this study, we sequence partial mitochondrial 12S rRNA and cyt b genes for seven Late Pleistocene porcupine individuals from Northern, Southern and Central China. Phylogenetic analyses show that the Tianyuan Cave porcupines, which had been morphologically identified as Hystrix subcristata, have a closer relationship to Hystrix brachyura.

Conclusion: Together with morphological adaptation characteristics, associated fauna, and climate change evidence, the molecular results reveal that a Late Quaternary extirpation has occurred during the evolutionary history of porcupines.
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http://dx.doi.org/10.1186/s12862-020-01656-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7368748PMC
July 2020

Binding affinities of 438 HLA proteins to complete proteomes of seven pandemic viruses and distributions of strongest and weakest HLA peptide binders in populations worldwide.

HLA 2020 09 11;96(3):277-298. Epub 2020 Jun 11.

Anthropology Unit, Department of Genetics and Evolution, University of Geneva, Geneva, Switzerland.

We report detailed peptide-binding affinities between 438 HLA Class I and Class II proteins and complete proteomes of seven pandemic human viruses, including coronaviruses, influenza viruses and HIV-1. We contrast these affinities with HLA allele frequencies across hundreds of human populations worldwide. Statistical modelling shows that peptide-binding affinities classified into four distinct categories depend on the HLA locus but that the type of virus is only a weak predictor, except in the case of HIV-1. Among the strong HLA binders (IC ≤ 50), we uncovered 16 alleles (the top ones being A*02:02, B*15:03 and DRB1*01:02) binding more than 1% of peptides derived from all viruses, 9 (top ones including HLA-A*68:01, B*15:25, C*03:02 and DRB1*07:01) binding all viruses except HIV-1, and 15 (top ones A*02:01 and C*14:02) only binding coronaviruses. The frequencies of strongest and weakest HLA peptide binders differ significantly among populations from different geographic regions. In particular, Indigenous peoples of America show both higher frequencies of strongest and lower frequencies of weakest HLA binders. As many HLA proteins are found to be strong binders of peptides derived from distinct viral families, and are hence promiscuous (or generalist), we discuss this result in relation to possible signatures of natural selection on HLA promiscuous alleles due to past pathogenic infections. Our findings are highly relevant for both evolutionary genetics and the development of vaccine therapies. However they should not lead to forget that individual resistance and vulnerability to diseases go beyond the sole HLA allelic affinity and depend on multiple, complex and often unknown biological, environmental and other variables.
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http://dx.doi.org/10.1111/tan.13956DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7300650PMC
September 2020

genozip: a fast and efficient compression tool for VCF files.

Bioinformatics 2020 07;36(13):4091-4092

School of Biological Sciences, The Environment Institute, Faculty of Sciences, The University of Adelaide, Adelaide, SA 5005, Australia.

Motivation: genozip is a new lossless compression tool for Variant Call Format (VCF) files. By applying field-specific algorithms and fully utilizing the available computational hardware, genozip achieves the highest compression ratios amongst existing lossless compression tools known to the authors, at speeds comparable with the fastest multi-threaded compressors.

Availability And Implementation: genozip is freely available to non-commercial users. It can be installed via conda-forge, Docker Hub, or downloaded from github.com/divonlan/genozip.

Supplementary Information: Supplementary data are available at Bioinformatics online.
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http://dx.doi.org/10.1093/bioinformatics/btaa290DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7332572PMC
July 2020

A Paleogenomic Reconstruction of the Deep Population History of the Andes.

Cell 2020 05 7;181(5):1131-1145.e21. Epub 2020 May 7.

Harvard Peabody Museum, Harvard University, Cambridge, MA 02138, USA.

There are many unanswered questions about the population history of the Central and South Central Andes, particularly regarding the impact of large-scale societies, such as the Moche, Wari, Tiwanaku, and Inca. We assembled genome-wide data on 89 individuals dating from ∼9,000-500 years ago (BP), with a particular focus on the period of the rise and fall of state societies. Today's genetic structure began to develop by 5,800 BP, followed by bi-directional gene flow between the North and South Highlands, and between the Highlands and Coast. We detect minimal admixture among neighboring groups between ∼2,000-500 BP, although we do detect cosmopolitanism (people of diverse ancestries living side-by-side) in the heartlands of the Tiwanaku and Inca polities. We also highlight cases of long-range mobility connecting the Andes to Argentina and the Northwest Andes to the Amazon Basin. VIDEO ABSTRACT.
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http://dx.doi.org/10.1016/j.cell.2020.04.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7304944PMC
May 2020

Spatiotemporal landscape genetics: Investigating ecology and evolution through space and time.

Mol Ecol 2020 01 17;29(2):218-246. Epub 2019 Dec 17.

Australian Centre for Ancient DNA, School of Biological Sciences, Environment Institute, University of Adelaide, Adelaide, South Australia, Australia.

Genetic time-series data from historical samples greatly facilitate inference of past population dynamics and species evolution. Yet, although climate and landscape change are often touted as post-hoc explanations of biological change, our understanding of past climate and landscape change influences on evolutionary processes is severely hindered by the limited application of methods that directly relate environmental change to species dynamics through time. Increased integration of spatiotemporal environmental and genetic data will revolutionize the interpretation of environmental influences on past population processes and the quantification of recent anthropogenic impacts on species, and vastly improve prediction of species responses under future climate change scenarios, yielding widespread revelations across evolutionary biology, landscape ecology and conservation genetics. This review encourages greater use of spatiotemporal landscape genetic analyses that explicitly link landscape, climate and genetic data through time by providing an overview of analytical approaches for integrating historical genetic and environmental data in five key research areas: population genetic structure, demography, phylogeography, metapopulation connectivity and adaptation. We also include a tabular summary of key methodological information, suggest approaches for mitigating the particular difficulties in applying these techniques to ancient DNA and palaeoclimate data, and highlight areas for future methodological development.
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http://dx.doi.org/10.1111/mec.15315DOI Listing
January 2020

Ancient DNA Reconstructs the Genetic Legacies of Precontact Puerto Rico Communities.

Mol Biol Evol 2020 03;37(3):611-626

School of Human Evolution and Social Change, Arizona State University, Tempe, AZ.

Indigenous peoples have occupied the island of Puerto Rico since at least 3000 BC. Due to the demographic shifts that occurred after European contact, the origin(s) of these ancient populations, and their genetic relationship to present-day islanders, are unclear. We use ancient DNA to characterize the population history and genetic legacies of precontact Indigenous communities from Puerto Rico. Bone, tooth, and dental calculus samples were collected from 124 individuals from three precontact archaeological sites: Tibes, Punta Candelero, and Paso del Indio. Despite poor DNA preservation, we used target enrichment and high-throughput sequencing to obtain complete mitochondrial genomes (mtDNA) from 45 individuals and autosomal genotypes from two individuals. We found a high proportion of Native American mtDNA haplogroups A2 and C1 in the precontact Puerto Rico sample (40% and 44%, respectively). This distribution, as well as the haplotypes represented, supports a primarily Amazonian South American origin for these populations and mirrors the Native American mtDNA diversity patterns found in present-day islanders. Three mtDNA haplotypes from precontact Puerto Rico persist among Puerto Ricans and other Caribbean islanders, indicating that present-day populations are reservoirs of precontact mtDNA diversity. Lastly, we find similarity in autosomal ancestry patterns between precontact individuals from Puerto Rico and the Bahamas, suggesting a shared component of Indigenous Caribbean ancestry with close affinity to South American populations. Our findings contribute to a more complete reconstruction of precontact Caribbean population history and explore the role of Indigenous peoples in shaping the biocultural diversity of present-day Puerto Ricans and other Caribbean islanders.
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http://dx.doi.org/10.1093/molbev/msz267DOI Listing
March 2020

More Arrows in the Ancient DNA Quiver: Use of Paleoepigenomes and Paleomicrobiomes to Investigate Animal Adaptation to Environment.

Mol Biol Evol 2020 02;37(2):307-319

Australian Centre for Ancient DNA, School of Biological Sciences, Environment Institute, University of Adelaide, Adelaide, South Australia, Australia.

Whether and how epigenetic mechanisms and the microbiome play a role in mammalian adaptation raised considerable attention and controversy, mainly because they have the potential to add new insights into the Modern Synthesis. Recent attempts to reconcile neo-Darwinism and neo-Lamarckism in a unified theory of molecular evolution give epigenetic mechanisms and microbiome a prominent role. However, supporting empirical data are still largely missing. Because experimental studies using extant animals can hardly be done over evolutionary timescales, we propose that advances in ancient DNA techniques provide a valid alternative. In this piece, we evaluate 1) the possible roles of epigenomes and microbiomes in animal adaptation, 2) advances in the retrieval of paleoepigenome and paleomicrobiome data using ancient DNA techniques, and 3) the plasticity of either and interactions between the epigenome and the microbiome, while emphasizing that it is essential to take both into account, as well as the underlying genetic factors that may confound the findings. We propose that advanced ancient DNA techniques should be applied to a wide range of past animals, so novel dynamics in animal evolution and adaption can be revealed.
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http://dx.doi.org/10.1093/molbev/msz231DOI Listing
February 2020

A strategy for building and using a human reference pangenome.

F1000Res 2019 14;8:1751. Epub 2019 Oct 14.

McDonnell Genome Institute, Washington University in St Louis, St Louis, MO, 63108, USA.

In March 2019, 45 scientists and software engineers from around the world converged at the University of California, Santa Cruz for the first pangenomics codeathon. The purpose of the meeting was to propose technical specifications and standards for a usable human pangenome as well as to build relevant tools for genome graph infrastructures. During the meeting, the group held several intense and productive discussions covering a diverse set of topics, including advantages of graph genomes over a linear reference representation, design of new methods that can leverage graph-based data structures, and novel visualization and annotation approaches for pangenomes. Additionally, the participants self-organized themselves into teams that worked intensely over a three-day period to build a set of pipelines and tools for specific pangenomic applications. A summary of the questions raised and the tools developed are reported in this manuscript.
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http://dx.doi.org/10.12688/f1000research.19630.2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8350888.2PMC
October 2019

Race in a genome: long read sequencing, ethnicity-specific reference genomes and the shifting horizon of race.

J Anthropol Sci 2019 Dec 7;96:91-106. Epub 2019 Oct 7.

Australian Centre for Ancient DNA, School of Biological Science, Environment Institute, The University of Adelaide, Adelaide SA 5005, Australia,

The sequencing of the human genome at the turn of the 21st century was hailed as revealing the overwhelming genetic similarity of human groups. Scholars of genomics have critiqued the subsequent persistence of race-based genetic science, but were reassured that the wide availability of gene sequencing would end the use of race as a proxy for genetic difference. Once an individual's whole gene sequence could be read, they hoped, their ethnoracial classification would become redundant. At the same time, genome science was recognising that the differences between human genomes went beyond the genome sequence to the structure of the genome itself. 'Structural variation' between genomes, including insertions, deletions, translocations, inversions, and copy number variations, mean that the 'universal' reference genome used for genome sequencing is not so universal. As conventional, 'short-read' sequencing wrongly assumes that all genomes have the same structure, significant genetic variation can be missed. This paper examines the twin phenomena that have been posed as a solution to the biases of short-read sequencing: 'long-read' sequencing and 'ethnicity-specific reference genomes'. Long-read sequencing is a method of generating a genome sequence that can be assembled de novo rather than relying on the reference genome. In recent years, a number of countries including China, Korea, and Denmark have used long-read sequencing and de novo assembly to develop 'national' reference genomes. Our analysis of one ethnicity-specific reference genome project, the Korean Reference Genome (KOREF), finds that it unduly emphasises the importance of population structural variation, framed in nationalist terms, and discounts the importance of individual structural variation. We argue that the intellectual labour required to make a Korean reference genome a coherent concept works to extend the horizon of race, prolonging the temporality of the 'meantime' in which race remains a seemingly valid concept in genomic science.
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http://dx.doi.org/10.4436/JASS.97004DOI Listing
December 2019

Widespread male sex bias in mammal fossil and museum collections.

Proc Natl Acad Sci U S A 2019 09 3;116(38):19019-19024. Epub 2019 Sep 3.

Australian Centre for Ancient DNA, The University of Adelaide, Adelaide, SA 5005, Australia;

A recent study of mammoth subfossil remains has demonstrated the potential of using relatively low-coverage high-throughput DNA sequencing to genetically sex specimens, revealing a strong male-biased sex ratio [P. Pečnerová et al., 27, 3505-3510.e3 (2017)]. Similar patterns were predicted for steppe bison, based on their analogous female herd-based structure. We genetically sexed subfossil remains of 186 Holarctic bison ( spp.), and also 91 brown bears (), which are not female herd-based, and found that ∼75% of both groups were male, very close to the ratio observed in mammoths (72%). This large deviation from a 1:1 ratio was unexpected, but we found no evidence for sex differences with respect to DNA preservation, sample age, material type, or overall spatial distribution. We further examined ratios of male and female specimens from 4 large museum mammal collections and found a strong male bias, observable in almost all mammalian orders. We suggest that, in mammals at least, 1) wider male geographic ranges can lead to considerably increased chances of detection in fossil studies, and 2) sexual dimorphic behavior or appearance can facilitate a considerable sex bias in fossil and modern collections, on a previously unacknowledged scale. This finding has major implications for a wide range of studies of fossil and museum material.
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http://dx.doi.org/10.1073/pnas.1903275116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6754617PMC
September 2019

Low-cost cross-taxon enrichment of mitochondrial DNA using in-house synthesised RNA probes.

PLoS One 2019 4;14(2):e0209499. Epub 2019 Feb 4.

Australian Centre for Ancient DNA, University of Adelaide, Adelaide, Australia.

Hybridization capture with in-solution oligonucleotide probes has quickly become the preferred method for enriching specific DNA loci from degraded or ancient samples prior to high-throughput sequencing (HTS). Several companies synthesize sets of probes for in-solution hybridization capture, but these commercial reagents are usually expensive. Methods for economical in-house probe synthesis have been described, but they do not directly address one of the major advantages of commercially synthesised probes: that probe sequences matching many species can be synthesised in parallel and pooled. The ability to make "phylogenetically diverse" probes increases the cost-effectiveness of commercial probe sets, as they can be used across multiple projects (or for projects involving multiple species). However, it is labour-intensive to replicate this with in-house methods, as template molecules must first be generated for each species of interest. While it has been observed that probes can be used to enrich for phylogenetically distant targets, the ability of this effect to compensate for the lack of phylogenetically diverse probes in in-house synthesised probe sets has not been tested. In this study, we present a refined protocol for in-house RNA probe synthesis and evaluated the ability of probes generated using this method from a single species to successfully enrich for the target locus in phylogenetically distant species. We demonstrated that probes synthesized using long-range PCR products from a placental mammal mitochondrion (Bison spp.) could be used to enrich for mitochondrial DNA in birds and marsupials (but not plants). Importantly, our results were obtained for approximately a third of the cost of similar commercially available reagents.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0209499PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6361428PMC
October 2019

Reconstructing the Deep Population History of Central and South America.

Cell 2018 11 8;175(5):1185-1197.e22. Epub 2018 Nov 8.

Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig 04103, Germany.

We report genome-wide ancient DNA from 49 individuals forming four parallel time transects in Belize, Brazil, the Central Andes, and the Southern Cone, each dating to at least ∼9,000 years ago. The common ancestral population radiated rapidly from just one of the two early branches that contributed to Native Americans today. We document two previously unappreciated streams of gene flow between North and South America. One affected the Central Andes by ∼4,200 years ago, while the other explains an affinity between the oldest North American genome associated with the Clovis culture and the oldest Central and South Americans from Chile, Brazil, and Belize. However, this was not the primary source for later South Americans, as the other ancient individuals derive from lineages without specific affinity to the Clovis-associated genome, suggesting a population replacement that began at least 9,000 years ago and was followed by substantial population continuity in multiple regions.
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http://dx.doi.org/10.1016/j.cell.2018.10.027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6327247PMC
November 2018

Molecular resolution to a morphological controversy: The case of North American fossil muskoxen Bootherium and Symbos.

Mol Phylogenet Evol 2018 12 16;129:70-76. Epub 2018 Aug 16.

Australian Centre for Ancient DNA (ACAD), School of Biological Sciences, Environment Institute, University of Adelaide, Australia. Electronic address:

The musk ox (Ovibos moschatus) is the only surviving member of a group of Pleistocene North American musk ox genera (Praeovibos, Ovibos, Bootherium, Euceratherium, and Soergelia) whose taxonomy is uncertain. The helmeted musk ox (Bootherium bombifrons) and the woodland musk ox (Symbos cavifrons) have been synonymised as male and female forms of a single Nearctic species found from Alaska, in the north, to Texas, in the south. However, this reclassification has not been tested using molecular data, despite the potential to use ancient DNA to examine these late Pleistocene taxa. In the present study, we sequenced mitochondrial genomes from seven subfossil musk ox specimens (originally identified as Bootherium and/or Symbos), allowing us to evaluate the identity of these muskoxen, explore their phylogeography, and estimate the timeline for their evolution. We also used nuclear genomic data to determine the sex of six of our seven samples. Ultimately, our molecular data support the synonymisation of the North American muskoxen Bootherium and Symbos.
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http://dx.doi.org/10.1016/j.ympev.2018.08.008DOI Listing
December 2018

Current evidence allows multiple models for the peopling of the Americas.

Sci Adv 2018 08 8;4(8):eaat5473. Epub 2018 Aug 8.

Department of Anthropology, University of Wyoming, Laramie, WY 82071, USA.

Some recent academic and popular literature implies that the problem of the colonization of the Americas has been largely resolved in favor of one specific model: a Pacific coastal migration, dependent on high marine productivity, from the Bering Strait to South America, thousands of years before Clovis, the earliest widespread cultural manifestation south of the glacial ice. Speculations on maritime adaptations and typological links (stemmed points) across thousands of kilometers have also been advanced. A review of the current genetic, archeological, and paleoecological evidence indicates that ancestral Native American population expansion occurred after 16,000 years ago, consistent with the archeological record, particularly with the earliest securely dated sites after ~15,000 years ago. These data are largely consistent with either an inland (ice-free corridor) or Pacific coastal routes (or both), but neither can be rejected at present. Systematic archeological and paleoecological investigations, informed by geomorphology, are required to test each hypothesis.
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http://dx.doi.org/10.1126/sciadv.aat5473DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6082647PMC
August 2018

Molecular phylogenetics supports the origin of an endemic Balearic shrew lineage (Nesiotites) coincident with the Messinian Salinity Crisis.

Mol Phylogenet Evol 2018 08 31;125:188-195. Epub 2018 Mar 31.

Departament de Biodiversitat i Conservació, Institut Mediterrani d'Estudis Avançats (CSIC-UIB), Esporles, Illes Balears, Spain. Electronic address:

The red-toothed shrews (Soricinae) are the most widespread subfamily of shrews, distributed from northern South America to North America and Eurasia. Within this subfamily, the tribe Nectogalini includes the fossil species Nesiotites hidalgo recorded from the Late Pleistocene to Holocene of the Balearic Islands (Western Mediterranean). Although there is a consensus about the close relationship between the extinct red-toothed shrew genera Nesiotites and Asoriculus based on morphology, molecular data are necessary to further evaluate the phylogenetic relationships of the Balearic fossils. We obtained a near complete mitochondrial genome of N. hidalgo, allowing the first molecular phylogenetic analysis of this species. Analyses based on 15,167 bp of the mitochondrial genome placed N. hidalgo as close relative to the extant Himalayan shrew (Soriculus nigrescens), and a combined analysis using molecular and morphological data confirm that N. hidalgo and Asoriculus gibberodon are sister-taxa with S. nigrescens as the immediate outgroup. Molecular clock and divergence estimates suggest that the split between N. hidalgo and its closest living relative occurred around 6.44 Ma, which is in agreement with the previously proposed colonisation of the Balearic Islands from mainland Europe by nectogaline shrews during the Messinian Salinity Crisis (5.97-5.33 My ago). Our results highlight that it is possible to retrieve genetic data from extinct small mammals from marginal environments for DNA preservation. Additional finds from the fossil record of Soricinae from the Eurasian Late Miocene/Early Pliocene are needed to shed further light on the still confusing taxonomy and paleobiogeography of this clade.
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http://dx.doi.org/10.1016/j.ympev.2018.03.028DOI Listing
August 2018

Genome of the Tasmanian tiger provides insights into the evolution and demography of an extinct marsupial carnivore.

Nat Ecol Evol 2018 Jan 11;2(1):182-192. Epub 2017 Dec 11.

School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia.

The Tasmanian tiger or thylacine (Thylacinus cynocephalus) was the largest carnivorous Australian marsupial to survive into the modern era. Despite last sharing a common ancestor with the eutherian canids ~160 million years ago, their phenotypic resemblance is considered the most striking example of convergent evolution in mammals. The last known thylacine died in captivity in 1936 and many aspects of the evolutionary history of this unique marsupial apex predator remain unknown. Here we have sequenced the genome of a preserved thylacine pouch young specimen to clarify the phylogenetic position of the thylacine within the carnivorous marsupials, reconstruct its historical demography and examine the genetic basis of its convergence with canids. Retroposon insertion patterns placed the thylacine as the basal lineage in Dasyuromorphia and suggest incomplete lineage sorting in early dasyuromorphs. Demographic analysis indicated a long-term decline in genetic diversity starting well before the arrival of humans in Australia. In spite of their extraordinary phenotypic convergence, comparative genomic analyses demonstrated that amino acid homoplasies between the thylacine and canids are largely consistent with neutral evolution. Furthermore, the genes and pathways targeted by positive selection differ markedly between these species. Together, these findings support models of adaptive convergence driven primarily by cis-regulatory evolution.
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http://dx.doi.org/10.1038/s41559-017-0417-yDOI Listing
January 2018

Parallel palaeogenomic transects reveal complex genetic history of early European farmers.

Nature 2017 11 8;551(7680):368-372. Epub 2017 Nov 8.

Laczkó Dezso˝ Museum, Veszprém 8200, Hungary.

Ancient DNA studies have established that Neolithic European populations were descended from Anatolian migrants who received a limited amount of admixture from resident hunter-gatherers. Many open questions remain, however, about the spatial and temporal dynamics of population interactions and admixture during the Neolithic period. Here we investigate the population dynamics of Neolithization across Europe using a high-resolution genome-wide ancient DNA dataset with a total of 180 samples, of which 130 are newly reported here, from the Neolithic and Chalcolithic periods of Hungary (6000-2900 bc, n = 100), Germany (5500-3000 bc, n = 42) and Spain (5500-2200 bc, n = 38). We find that genetic diversity was shaped predominantly by local processes, with varied sources and proportions of hunter-gatherer ancestry among the three regions and through time. Admixture between groups with different ancestry profiles was pervasive and resulted in observable population transformation across almost all cultural transitions. Our results shed new light on the ways in which gene flow reshaped European populations throughout the Neolithic period and demonstrate the potential of time-series-based sampling and modelling approaches to elucidate multiple dimensions of historical population interactions.
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http://dx.doi.org/10.1038/nature24476DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5973800PMC
November 2017

Megafaunal isotopes reveal role of increased moisture on rangeland during late Pleistocene extinctions.

Nat Ecol Evol 2017 Apr 18;1(5):125. Epub 2017 Apr 18.

Australian Centre for Ancient DNA, University of Adelaide, North Terrace, South Australia 5005, Australia.

The role of environmental change in the late Pleistocene megafaunal extinctions remains a key question, owing in part to uncertainty about landscape changes at continental scales. We investigated the influence of environmental changes on megaherbivores using bone collagen nitrogen isotopes (n = 684, 63 new) as a proxy for moisture levels in the rangelands that sustained late Pleistocene grazers. An increase in landscape moisture in Europe, Siberia and the Americas during the Last Glacial-Interglacial Transition (LGIT; ~25-10 kyr bp) directly affected megaherbivore ecology on four continents, and was associated with a key period of population decline and extinction. In all regions, the period of greatest moisture coincided with regional deglaciation and preceded the widespread formation of wetland environments. Moisture-driven environmental changes appear to have played an important part in the late Quaternary megafaunal extinctions through alteration of environments such as rangelands, which supported a large biomass of specialist grazers. On a continental scale, LGIT moisture changes manifested differently according to regional climate and geography, and the stable presence of grasslands surrounding the central forested belt of Africa during this period helps to explain why proportionally fewer African megafauna became extinct during the late Pleistocene.
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http://dx.doi.org/10.1038/s41559-017-0125DOI Listing
April 2017
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