Modern humans arrived in Europe ~45,000 years ago, but little is known about their genetic composition before the start of farming ~8,500 years ago. Here we analyse genome-wide data from 51 Eurasians from ~45,000–7,000 years ago. Over this time, the proportion of Neanderthal DNA decreased from 3–6% to around 2%, consistent with natural selection against Neanderthal variants in modern humans. Whereas there is no evidence of the earliest modern humans in Europe contributing to the genetic composition of present-day Europeans, all individuals between ~37,000 and ~14,000 years ago descended from a single founder population which forms part of the ancestry of present-day Europeans. An ~35,000-year-old individual from northwest Europe represents an early branch of this founder population which was then displaced across a broad region, before reappearing in southwest Europe at the height of the last Ice Age ~19,000 years ago. During the major warming period after ~14,000 years ago, a genetic component related to present-day Near Easterners became widespread in Europe. These results document how population turnover and migration have been recurring themes of European prehistory.

Genetic similarity among late Neanderthals is predicted well by their geographical location, and although some of these Neanderthals were contemporaneous with early modern humans, their genomes show no evidence of recent gene flow from modern humans. Many questions remain about the relationship between populations of Neanderthals around the time of their final interactions with modern humans, and how this contributed to the evolution of modern humans. Janet Kelso, Svante Pääbo and colleagues sequenced the genomes of five Neanderthals that lived between 39,000 and 47,000 years ago, broadening the temporal and geographical range of available Neanderthal genomes. They analyse these genomes together with previously sequenced ancient genomes and find that relatedness among Neanderthals is related to geographic proximity. They find that the majority of gene flow into early modern humans originated from one or more Neanderthal populations that diverged from the late Neanderthals at least 70,000 years ago, but after their split from the Altai Neanderthal approximately 150,000 years ago. Although it has previously been shown that Neanderthals contributed DNA to modern humans1,2, not much is known about the genetic diversity of Neanderthals or the relationship between late Neanderthal populations at the time at which their last interactions with early modern humans occurred and before they eventually disappeared. Our ability to retrieve DNA from a larger number of Neanderthal individuals has been limited by poor preservation of endogenous DNA3 and contamination of Neanderthal skeletal remains by large amounts of microbial and present-day human DNA3,4,5. Here we use hypochlorite treatment6 of as little as 9 mg of bone or tooth powder to generate between 1- and 2.7-fold genomic coverage of five Neanderthals who lived around 39,000 to 47,000 years ago (that is, late Neanderthals), thereby doubling the number of Neanderthals for which genome sequences are available. Genetic similarity among late Neanderthals is well predicted by their geographical location, and comparison to the genome of an older Neanderthal from the Caucasus2,7 indicates that a population turnover is likely to have occurred, either in the Caucasus or throughout Europe, towards the end of Neanderthal history. We find that the bulk of Neanderthal gene flow into early modern humans originated from one or more source populations that diverged from the Neanderthals that were studied here at least 70,000 years ago, but after they split from a previously sequenced Neanderthal from Siberia2 around 150,000 years ago. Although four of the Neanderthals studied here post-date the putative arrival of early modern humans into Europe, we do not detect any recent gene flow from early modern humans in their ancestry.

Modern humans have populated Europe for more than 45,000 years^1,2. Our knowledge of the genetic relatedness and structure of ancient hunter-gatherers is however limited, owing to the scarceness and poor molecular preservation of human remains from that period³. Here we analyse 356 ancient hunter-gatherer genomes, including new genomic data for 116 individuals from 14 countries in western and central Eurasia, spanning between 35,000 and 5,000 years ago. We identify a genetic ancestry profile in individuals associated with Upper Palaeolithic Gravettian assemblages from western Europe that is distinct from contemporaneous groups related to this archaeological culture in central and southern Europe⁴, but resembles that of preceding individuals associated with the Aurignacian culture. This ancestry profile survived during the Last Glacial Maximum (25,000 to 19,000 years ago) in human populations from southwestern Europe associated with the Solutrean culture, and with the following Magdalenian culture that re-expanded northeastward after the Last Glacial Maximum. Conversely, we reveal a genetic turnover in southern Europe suggesting a local replacement of human groups around the time of the Last Glacial Maximum, accompanied by a north-to-south dispersal of populations associated with the Epigravettian culture. From at least 14,000 years ago, an ancestry related to this culture spread from the south across the rest of Europe, largely replacing the Magdalenian-associated gene pool. After a period of limited admixture that spanned the beginning of the Mesolithic, we find genetic interactions between western and eastern European hunter-gatherers, who were also characterized by marked differences in phenotypically relevant variants.

Y chromosome evolution in Neanderthals: The genomes of archaic hominins have been sequenced and compared with that of modern humans. However, most archaic individuals with high-quality sequences available have been female. Petr et al. performed targeted sequencing of the paternally inherited Y chromosomes from three Neanderthals and two Denisovans (see the Perspective by Schierup). Comparisons with available archaic and diverse modern human Y chromosomes indicated that, similar to the maternally inherited mitochondria, the human and Neanderthal Y chromosomes were more closely related to each other compared with the Denisovan Y chromosome. This result supports the conclusion that interbreeding between early humans and Neanderthals and selection replaced the more ancient Denisovian-like Y chromosome and mitochondria in Neanderthals. Science , this issue p. 1653 ; see also p. 1565

Significance: The microbiome plays key roles in human health, but little is known about its evolution. We investigate the evolutionary history of the African hominid oral microbiome by analyzing dental biofilms of humans and Neanderthals spanning the past 100,000 years and comparing them with those of chimpanzees, gorillas, and howler monkeys. We identify 10 core bacterial genera that have been maintained within the human lineage and play key biofilm structural roles. However, many remain understudied and unnamed. We find major taxonomic and functional differences between the oral microbiomes of Homo and chimpanzees but a high degree of similarity between Neanderthals and modern humans, including an apparent Homo -specific acquisition of starch digestion capability in oral streptococci, suggesting microbial coadaptation with host diet.