Insights into Modern Human Prehistory Using Ancient Genomes

Recent positive selection signatures reveal phenotypic evolution in the Han Chinese population

Characterizing natural selection signatures and relationships with phenotype spectra is important for understanding human evolution and both biological and pathological mechanisms. Here, we identified 24 genetic loci under recent selection by analyzing rare singletons in 3946 high-depth whole-genome sequencing data of Han Chinese. The loci include immune-related gene regions (MHC cluster, IGH cluster, STING1, and PSG), alcohol metabolism-related gene regions (ADH1B, ALDH2, and ALDH3B2), and the olfactory perception gene OR4C16, in which the MHC cluster, ADH1B, and ALDH2 were also identified by TOPMed and WestLake Biobank. Among the signals, the IGH cluster is particularly interesting, in which the favored allele of variant 14_105737776_C_T (rs117518546, IgG1-G396R) promotes immune response, but also increases the risk of an autoimmune disease systemic lupus erythematosus (SLE). It is also surprising that our newly discovered ALDH3B2 evolved in the opposite direction to ALDH2 for alcohol metabolism. Besides monogenic traits, we found that multiple complex traits experienced polygenic adaptation. Particularly, multi-methods consistently revealed that lower blood pressure was favored in natural selection. Finally, we built a database named RePoS (recent positive selection, http://bigdata.ibp.ac.cn/RePoS/) to integrate and display multi-population selection signals. Our study extended our understanding of natural evolution and phenotype adaptation in Han Chinese as well as other populations.

Genomes from historical Drosophila melanogaster specimens illuminate adaptive and demographic changes across more than 200 years of evolution

The ability to perform genomic sequencing on long-dead organisms is opening new frontiers in evolutionary research. These opportunities are especially notable in the case of museum collections, from which countless documented specimens may now be suitable for genomic analysis-if data of sufficient quality can be obtained. Here, we report 25 newly sequenced genomes from museum specimens of the model organism Drosophila melanogaster, including the oldest extant specimens of this species. By comparing historical samples ranging from the early 1800s to 1933 against modern-day genomes, we document evolution across thousands of generations, including time periods that encompass the species' initial occupation of northern Europe and an era of rapidly increasing human activity. We also find that the Lund, Sweden population underwent local genetic differentiation during the early 1800s to 1933 interval (potentially due to drift in a small population) but then became more similar to other European populations thereafter (potentially due to increased migration). Within each century-scale time period, our temporal sampling allows us to document compelling candidates for recent natural selection. In some cases, we gain insights regarding previously implicated selection candidates, such as ChKov1, for which our inferred timing of selection favors the hypothesis of antiviral resistance over insecticide resistance. Other candidates are novel, such as the circadian-related gene Ahcy, which yields a selection signal that rivals that of the DDT resistance gene Cyp6g1. These insights deepen our understanding of recent evolution in a model system, and highlight the potential of future museomic studies.

Origin and Spread of the ALDH2 Glu504Lys Allele

Gene polymorphism of acetaldehyde dehydrogenase 2 (ALDH2), a key enzyme for alcohol metabolism in humans, can affect catalytic activity. The ALDH2 Glu504Lys mutant allele has a high-frequency distribution in East Asian populations and has been demonstrated to be associated with an increased risk of cardiovascular disease, stroke, and tumors. Available evidence suggests that the evolution of the ALDH2 gene has been influenced by multiple factors. Random mutations produce Glu504Lys, and genetic drift alters the frequency of this allele; additionally, environmental factors such as hepatitis B virus infection and high-elevation hypoxia affect its frequency through selective effects, ultimately resulting in a high frequency of this allele in East Asian populations. Here, the origin, selection, and spread of the ALDH2 Glu504Lys allele are discussed, and an outlook for further research is proposed to realize a precision medical strategy based on the genetic and environmental variations in ALDH2.

Insights into human history from the first decade of ancient human genomics

[Figure: see text].

Projecting Ancient Ancestry in Modern-Day Arabians and Iranians: A Key Role of the Past Exposed Arabo-Persian Gulf on Human Migrations

The Arabian Peninsula is strategic for investigations centered on the early structuring of modern humans in the wake of the out-of-Africa migration. Despite its poor climatic conditions for the recovery of ancient human DNA evidence, the availability of both genomic data from neighboring ancient specimens and informative statistical tools allow modeling the ancestry of local modern populations. We applied this approach to a data set of 741,000 variants screened in 291 Arabians and 78 Iranians, and obtained insightful evidence. The west-east axis was a strong forcer of population structure in the Peninsula, and, more importantly, there were clear continuums throughout time linking western Arabia with the Levant, and eastern Arabia with Iran and the Caucasus. Eastern Arabians also displayed the highest levels of the basal Eurasian lineage of all tested modern-day populations, a signal that was maintained even after correcting for a possible bias due to a recent sub-Saharan African input in their genomes. Not surprisingly, eastern Arabians were also the ones with highest similarity with Iberomaurusians, who were, so far, the best proxy for the basal Eurasians amongst the known ancient specimens. The basal Eurasian lineage is the signature of ancient non-Africans who diverged from the common European-eastern Asian pool before 50,000 years ago, prior to the later interbred with Neanderthals. Our results appear to indicate that the exposed basin of the Arabo-Persian Gulf was the possible home of basal Eurasians, a scenario to be further investigated by searching ancient Arabian human specimens.

Current Progress in Evolutionary Comparative Genomics of Great Apes

The availability of high-quality genome sequences of great ape species provides unprecedented opportunities for genomic analyses. Herein, we reviewed the recent progress in evolutionary comparative genomic studies of the existing great ape species, including human, chimpanzee, bonobo, gorilla, and orangutan. We elaborate discovery on evolutionary history, natural selection, structural variations, and new genes of these species, which is informative for understanding the origin of human-specific phenotypes.

Maternal genetic structure in ancient Shandong between 9500 and 1800 years ago

Archaeological and ancient DNA studies revealed that Shandong, a multi-culture center in northern coastal China, was home to ancient populations having ancestry related to both northern and southern East Asian populations. However, the limited temporal and geographical range of previous studies have been insufficient to describe the population history of this region in greater detail. Here, we report the analysis of 86 complete mitochondrial genomes from the remains of 9500 to 1800-year-old humans from 12 archaeological sites across Shandong. For samples older than 4600 years before present (BP), we found haplogroups D4, D5, B4c1, and B5b2, which are observed in present-day northern and southern East Asians. For samples younger than 4600 BP, haplogroups C (C7a1 and C7b), M9 (M9a1), and F (F1a1, F2a, and F4a1) begin to appear, indicating changes in the Shandong maternal genetic structure starting from the beginning of the Longshan cultural period. Within Shandong, the genetic exchange is possible between the coastal and inland regions after 3100 BP. We also discovered the B5b2 lineage in Shandong populations, with the oldest Bianbian individual likely related to the ancestors of some East Asians and North Asians. By reconstructing a maternal genetic structure of Shandong populations, we provide greater resolution of the population dynamics of the northern coastal East Asia over the past nine thousand years.

Human evolutionary history in Eastern Eurasia using insights from ancient DNA

Advances in ancient genomics are providing unprecedented insight into modern human history. Here, we review recent progress uncovering prehistoric populations in Eastern Eurasia based on ancient DNA studies from the Upper Pleistocene to the Holocene. Many ancient populations existed during the Upper Pleistocene of Eastern Eurasia-some with no substantial ancestry related to present-day populations, some with an affinity to East Asians, and some who contributed to Native Americans. By the Holocene, the genetic composition across East Asia greatly shifted, with several substantial migrations. Three are southward: an increase in northern East Asian-related ancestry in southern East Asia; movement of East Asian-related ancestry into Southeast Asia, mixing with Basal Asian ancestry; and movement of southern East Asian ancestry to islands of Southeast Asia and the Southwest Pacific through the expansion of Austronesians. We anticipate that additional ancient DNA will magnify our understanding of the genetic history in Eastern Eurasia.

A Southeast Asian origin for present-day non-African human Y chromosomes

The genomes of present-day humans outside Africa originated almost entirely from a single out-migration ~ 50,000–70,000 years ago, followed by mixture with Neanderthals contributing ~ 2% to all non-Africans. However, the details of this initial migration remain poorly understood because no ancient DNA analyses are available from this key time period, and interpretation of present-day autosomal data is complicated due to subsequent population movements/reshaping. One locus, however, does retain male-specific information from this early period: the Y chromosome, where a detailed calibrated phylogeny has been constructed. Three present-day Y lineages were carried by the initial migration: the rare haplogroup D, the moderately rare C, and the very common FT lineage which now dominates most non-African populations. Here, we show that phylogenetic analyses of haplogroup C, D and FT sequences, including very rare deep-rooting lineages, together with phylogeographic analyses of ancient and present-day non-African Y chromosomes, all point to East/Southeast Asia as the origin 50,000–55,000 years ago of all known surviving non-African male lineages (apart from recent migrants). This observation contrasts with the expectation of a West Eurasian origin predicted by a simple model of expansion from a source near Africa, and can be interpreted as resulting from extensive genetic drift in the initial population or replacement of early western Y lineages from the east, thus informing and constraining models of the initial expansion.

Present-Day DNA Contamination in Ancient DNA Datasets

Present-day contamination can lead to false conclusions in ancient DNA studies. A number of methods are available to estimate contamination, which use a variety of signals and are appropriate for different types of data. Here an overview of currently available methods highlighting their strengths and weaknesses is provided, and a classification based on the signals used to estimate contamination is proposed. This overview aims at enabling researchers to choose the most appropriate methods for their dataset. Based on this classification, potential avenues for the further development of methods are discussed.

Unlocking the origins and biology of domestic animals using ancient DNA and paleogenomics

Animal domestication has fascinated biologists since Charles Darwin first drew the parallel between evolution via natural selection and human-mediated breeding of livestock and companion animals. In this review we show how studies of ancient DNA from domestic animals and their wild progenitors and congeners have shed new light on the genetic origins of domesticates, and on the process of domestication itself. High-resolution paleogenomic data sets now provide unprecedented opportunities to explore the development of animal agriculture across the world. In addition, functional population genomics studies of domestic and wild animals can deliver comparative information useful for understanding recent human evolution.

PGG.SNV: understanding the evolutionary and medical implications of human single nucleotide variations in diverse populations

Despite the tremendous growth of the DNA sequencing data in the last decade, our understanding of the human genome is still in its infancy. To understand the implications of genetic variants in the light of population genetics and molecular evolution, we developed a database, PGG.SNV ( https://www.pggsnv.org ), which gives much higher weight to previously under-investigated indigenous populations in Asia. PGG.SNV archives 265 million SNVs across 220,147 present-day genomes and 1018 ancient genomes, including 1009 newly sequenced genomes, representing 977 global populations. Moreover, estimation of population genetic diversity and evolutionary parameters is available in PGG.SNV, a unique feature compared with other databases.

Palaeodemographic modelling supports a population bottleneck during the Pleistocene-Holocene transition in Iberia

Demographic change lies at the core of debates on genetic inheritance and resilience to climate change of prehistoric hunter-gatherers. Here we analyze the radiocarbon record of Iberia to reconstruct long-term changes in population levels and test different models of demographic growth during the Last Glacial-Interglacial transition. Our best fitting demographic model is composed of three phases. First, we document a regime of exponential population increase during the Late Glacial warming period (c.16.6-12.9 kya). Second, we identify a phase of sustained population contraction and stagnation, beginning with the cold episode of the Younger Dryas and continuing through the first half of the Early Holocene (12.9-10.2 kya). Finally, we report a third phase of density-dependent logistic growth (10.2-8 kya), with rapid population increase followed by stabilization. Our results support a population bottleneck hypothesis during the Last Glacial-Interglacial transition, providing a demographic context to interpret major shifts of prehistoric genetic groups in south-west Europe.

The archaeological record provides large ensembles of radiocarbon dates which can be used to infer long-term changes in human demography. Here, the authors analyse the radiocarbon record of the Iberian peninsula, finding support for a bottleneck during the Last Glacial-Interglacial transition

Mawangdui-Type Ancient Human Cadavers in China and Strategies for Their Long-Term Preservation

Ancient human remains may exist as intact cadavers in various forms, including mummies as well as humid or soft corpses. These valuable human depositories have been increasingly investigated with modern molecular biological approaches, delivering breakthrough discoveries in the field of paleoanthropology. Many ancient remains are also preserved in museums for public education of the history of human civilization. The Mawangdui tomb No. 1 cadaver was unearthed in 1972 in Changsha, China, and is a well-preserved humid-type corpse of a deceased woman who lived in the Western Han Dynasty (206BC-24AD). During the past few decades, a number of other similar cadavers have been discovered in China. The Mawangdui cadaver thus appears to represent an archetype of the humid corpses that are commonly unearthed from buried coffins, but show a great extent of anatomical and histological integrity at the time of excavation. Long-term protection of these cadavers is important with regard to scientific investigation and heritage conservation, while challenges exist to develop effective preservation protocols. In this perspective article, we describe the overall features of the humid cadavers found in China, and discuss the factors that potentially contributed to their preservation before excavation. We also introduce the efforts taken for, and experience learned from, postexcavation preservation of the Mawangdui cadaver during the past four decades. Finally, we propose that research into the mechanism governing the breakdown of macromolecules may provide potential solutions for extended protection of these valuable ancient human remains.

Limits of long-term selection against Neandertal introgression

Since the discovery that all non-Africans inherit 2% of their genomes from Neandertal ancestors, there has been a great interest in understanding the fate and effects of introgressed Neandertal DNA in modern humans. A number of recent studies have claimed that there has been continuous selection against introgressed Neandertal DNA over the last 55,000 years. Here, we show that there has been no long-term genome-wide removal of Neandertal DNA, and that the previous result was due to incorrect assumptions about gene flow between African and non-African populations. Nevertheless, selection did occur following introgression, and its effect was strongest in regulatory regions, suggesting that Neandertals may have differed from humans more in their regulatory than in their protein-coding sequences.

Several studies have suggested that introgressed Neandertal DNA was subjected to negative selection in modern humans. A striking observation in support of this is an apparent monotonic decline in Neandertal ancestry observed in modern humans in Europe over the past 45,000 years. Here, we show that this decline is an artifact likely caused by gene flow between modern human populations, which is not taken into account by statistics previously used to estimate Neandertal ancestry. When we apply a statistic that avoids assumptions about modern human demography by taking advantage of two high-coverage Neandertal genomes, we find no evidence for a change in Neandertal ancestry in Europe over the past 45,000 years. We use whole-genome simulations of selection and introgression to investigate a wide range of model parameters and find that negative selection is not expected to cause a significant long-term decline in genome-wide Neandertal ancestry. Nevertheless, these models recapitulate previously observed signals of selection against Neandertal alleles, in particular the depletion of Neandertal ancestry in conserved genomic regions. Surprisingly, we find that this depletion is strongest in regulatory and conserved noncoding regions and in the most conserved portion of protein-coding sequences.

Evidence of aortic dissection and Marfan syndrome in a mummy from the Capuchin Catacombs of Palermo, Sicily

The authors report on the assessment of an anthropogenic mummy of a young man from the Capuchin Catacombs of Palermo, Sicily, tentatively dated from the mid- to late 19^th century AD. The mummy was investigated by full-body CT examination. CT images clearly showed aortic dissection classified as Stanford-A. Due to the relation of aortic dissection to inherited connective tissue diseases in young people, such as Marfan syndrome, conspicuous and pathological findings possibly indicating the presence of underlying Marfan syndrome were assessed. Several systemic features were scored that supported the presence of underlying Marfan syndrome in this mummy. These findings were: pectus carinatum and chest asymmetry, dural ectasia, protrusio acetabuli, dolichocephaly, down-slanting palpebral fissures, malar hypoplasia and (probable) reduced elbow extension. Aortic dissection, a cardinal feature of Marfan syndrome, turned out to be the diagnostic key for the paleoradiological diagnosis of this disease. The demonstrated CT findings contribute to the spectrum of cardiovascular diseases and inherited connective tissue disease in the fields of paleopathology and paleoradiology.