Neanderthals and humans interbred in Europe for 5,400 years

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Neanderthals and humans interbred in Europe for 5,400 years Jun 22, 2015 5:38:33 GMT

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Post by Admin on Jun 22, 2015 5:38:33 GMT

In a paper titled “Rabbits and hominin survival in Iberia”, the authors put forward the proposal that the Neanderthals’ dependence on large animals for food may have reduced their survival chances. Our closest ancestors are known to have preferred to hunt large prey across woodlands rather than in large open spaces. However, as the climate began to quickly change these large animal became rarer and rarer, study co-author John Steward, a paleoecologist from the University of Bournemouth, is quoted as saying by Past Horizons. It seems, according to Steward, that Neanderthals could not master the skills and technology needed to hunt smaller, faster prey such as rabbits. Modern humans, on the other hand, created traps and used twine to catch rabbits, which bred in abundance in that region 30,000 years ago. Rabbits make for a very good food source because of the relative ease with which they can be caught, because of their fast breeding, and because of their predictability, Steward went on to explain. With access to such easy prey, modern humans were better equipped to deal with climate change and survive it. Yet it is worth noting that “the rabbit” factor may not have had the same effect in other parts of Europe, such as Italy, where these animals didn’t breed so abundantly.

High dependence on the hunting and consumption of large mammals by some hominins may have limited their survival once their preferred quarry became scarce or disappeared. Adaptation to smaller residual prey would have been essential after the many large-bodied species decreased in numbers. We focus on the use of a superabundant species, the rabbit, to demonstrate the importance of this taxon in Iberia as fundamental to predators. We show that the use of the rabbit over time has increased, and that there could have been differential consumption by Neanderthals and Anatomically Modern Humans (AMH). Analysis of bone remains from excavations throughout Iberia show that this lagomorph was a crucial part ofthe diet of AMH but was relatively unutilised during the Mousterian, when Neanderthals were present. We first present changes in mammalian biomass and mean body mass of mammals over 50,000 years, to illustrate the dramatic loss of large mammalian fauna and to show how the rabbit may have contributed a consistently high proportion of the available game biomass throughout that period. Unlike the Italian Peninsula and other parts of Europe, in Iberia the rabbit has provided a food resource of great importance for predators including hominins. We suggest that hunters that could shift focus to rabbits and other smaller residual fauna, once larger-bodied species decreased in numbers, would have been able to persist. From the evidence presented here, we postulate that Neanderthals may have been less capable of prey-shifting and hence use the high-biomass prey resource provided by the rabbit, to the extent AMH did.

Figure 2. Changes in the overall terrestrial mammalian standing biomass (kg/km−2) (grey bars), calculated for faunal assemblages from the Mousterian to the Mesolithic. The black line denotes the percentage contribution to the overall standing biomass made by the rabbit for each time period. MP = Middle Palaeolithic; UP = Upper Palaeolithic; M = Mesolithic. In this study, data for the Mousterian are from the latter stages of this period, between 70,000 and 40,000 BP, where warm and cold climatic regions were present.

Here we represent faunal assemblages for these two types of environments. The Iberian Peninsula constituted one of the southernmost limits of the steppe-tundra expanse and was occupied by these faunas during the coldest periods (Álvarez-Lao and García, 2011). In the Iberian fossil record, the presence of cold-adapted mammal species is occasional and restricted to specific time spans and, in most cases, to limited geographical areas. The sites that have yielded cold-adapted species are distributed irregularly along the Iberian Peninsula, most of them located in the north, where the climatology and landscapes are more similar to central European localities. It is likely that the Pyrenees and Cantabrian Mountain Range functioned as geographic barriers for some of these species. This faunal community is closely related with the steppe-tundra characteristic of the Pleistocene glacial periods, disappeared at the end of the Pleistocene alongside the mammoth fauna. After the end of the Pleistocene. Some of these species (reindeer, musk-ox and arctic fox) moved northward to arctic areas, a few others (as saiga antelope) migrated to the central Asian steppe and some other species (as woolly mammoth and woolly rhinoceros) became extinct. The loss of these megaherbivores is clearly observed in the drop in biomass shown in the graph. Although climatic differences in the north and south of the Iberian Peninsula also occurred within the other time periods, we have only differentiate these for the Mousterian because of the distinctiveness of the cold-adapted faunas that migrated from Eurasia.

Figure 4.

Relative to other mammal groups, rabbit bone abundance was always significantly higher during the Upper Palaeolithic (76%) and Mesolithic (59%) than during the Middle Palaeolithic (Fig. 4). The difference between the average rabbit remains and that of cervids, the second most abundant prey item, were less than 10% during the Mousterian. In contrast, during the Upper Palaeolithic and Mesolithic, the difference between the rabbit and the second-most important prey items was over 60% and 20%, respectively. After the rabbit, large ungulates (caprids, cervids and equids) were relatively important during the Middle and Upper Palaeolithic, while caprids, cervids and suids took that place during the Mesolithic (Fig. 4). Our evidence indicates that hominin diets may have changed from one dependent on large mammals during the Middle Palaeolithic to diets dominated by smaller species in the Upper Palaeolithic, in particular by the wild rabbit. The explanation for this transition is either that climate change negatively impacted large mammal populations, forcing prehistoric people to incorporate smaller vertebrate species into their diets, or that people themselves negatively impacted large mammal populations, which in turn forced foragers to add smaller species to their diets.

Journal of Human Evolution DOI: 10.1016/j.jhevol.2013.01.002

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Neanderthals and humans interbred in Europe for 5,400 years Jun 24, 2015 4:12:47 GMT

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Post by Admin on Jun 24, 2015 4:12:47 GMT

Neanderthals became extinct about 40,000 years ago but contributed on average one to three percent to the genomes of present-day Eurasians. Researchers have now analyzed DNA from a 37,000 to 42,000-year-old human mandible from Oase Cave in Romania and have found that six to nine percent of this person's genome came from Neanderthals, more than any other human sequenced to date. Because large segments of this individual's chromosomes are of Neanderthal origin, a Neanderthal was among his ancestors as recently as four to six generations back in his family tree. This shows that some of the first modern humans that came to Europe mixed with the local Neanderthals.

All present-day humans who have their roots outside sub-Saharan Africa carry one to three percent of Neanderthal DNA in their genomes. Until now, researchers have thought it most likely that early humans coming from Africa mixed with Neanderthals in the Middle East around 50,000 to 60,000 years ago, before spreading into Asia, Europe and the rest of the world. However, radiocarbon dating of remains from sites across Europe suggests that modern humans and Neanderthals both lived in Europe for up to 5,000 years and that they may have interbred there, too.

Figure 1: Allele sharing between the Oase 1 individual and other genomes. Each point indicates the extent to which the Oase 1 genome shares alleles with one or other of a pair of genomes from different populations indicated above and below (see Extended Data Table 1 for numbers).

In 2002, a 40,000-year-old jawbone was found by cavers in Oase Cave in south-western Romania and the site was subsequently studied by an international team led by the researchers of the Emil Racovita Institute of Speleology in Romania. Researchers from the Max Planck Institute for Evolutionary Anthropology (Germany), Harvard Medical School (USA), and the Key Laboratory of Vertebrate Evolution and Human Origins in Beijing (China) have now analyzed DNA from this fossil, which is one of the earliest modern-human remains found in Europe. They estimate that five to 11 percent of the genome preserved in the bone derives from a Neanderthal ancestor, including exceptionally large segments of some chromosomes. By estimating how lengths of DNA inherited from an ancestor shorten with each generation, the researchers estimated that the man had a Neanderthal ancestor in the previous four to six generations.

Figure 2: Spatial distribution of alleles matching Neanderthals in modern humans. Coloured vertical lines indicate alleles shared with Neanderthals and no colour indicates alleles shared with the great majority of West Africans. D, Dinka; F, French; H, Han; K, Kostenki 14; O, Oase 1; U, Ust’-Ishim.

And because Oase I doesn't share more alleles - a variant of a gene - with later Europeans than he does with East Asians, Reich said it suggests that this was a "pioneer" population, which didn't mix with modern Europeans. "If you try and understand how it is related to modern humans today, it doesn't bear a particular close relationship to modern day Europeans. It's actually slightly closer, if anything, to present day East Asians," Reich said. "For us, that was a surprise and very interesting and exciting," he said. "This sample seems to be part of an initial pioneer population of modern humans in Europe that overlapped with Neanderthals, interbred with them and kind of died out and was replaced by other waves of movement from other places. Those people (in Europe) today are descended from this later wave."

Neanderthals are thought to have disappeared in Europe approximately 39,000–41,000 years ago but they have contributed 1–3% of the DNA of present-day people in Eurasia1. Here we analyse DNA from a 37,000–42,000-year-old2 modern human from Peştera cu Oase, Romania. Although the specimen contains small amounts of human DNA, we use an enrichment strategy to isolate sites that are informative about its relationship to Neanderthals and present-day humans. We find that on the order of 6–9% of the genome of the Oase individual is derived from Neanderthals, more than any other modern human sequenced to date. Three chromosomal segments of Neanderthal ancestry are over 50 centimorgans in size, indicating that this individual had a Neanderthal ancestor as recently as four to six generations back. However, the Oase individual does not share more alleles with later Europeans than with East Asians, suggesting that the Oase population did not contribute substantially to later humans in Europe.

Qiaomei Fu, Mateja Hajdinjak, Oana Teodora Moldovan, Silviu Constantin, Swapan Mallick, Pontus Skoglund, Nick Patterson, Nadin Rohland, Iosif Lazaridis, Birgit Nickel, Bence Viola, Kay Prüfer, Matthias Meyer, Janet Kelso, David Reich, Svante Pääbo. An early modern human from Romania with a recent Neanderthal ancestor. Nature, 2015; DOI: 10.1038/nature14558

Last Edit: Apr 12, 2018 23:21:47 GMT by Admin

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Neanderthals and humans interbred in Europe for 5,400 years Jul 5, 2015 2:26:30 GMT

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Post by Admin on Jul 5, 2015 2:26:30 GMT

Today, we think that the discovery of neanderthal fossils were a revelation. At the time, they were just another thing to argue about. Here’s why one talented scientist confused a neanderthal with a Cossack.

Neanderthal remains came to light in the 1800s. One of the first sets of remains to be unearthed is what’s now known as Neanderthal 1, discovered in 1856 under meters of mud in a cave. If its discoverers expected praise, they were disappointed. Now we know it to be the remains of an early human. Back then, it was considered everything from a forgery to a failure of scientific observation.

One of the people leading the charge against it was Rudolf Virchow. Virchow was a dedicated and intelligent man, who used the wide range of his skills to examine disease from multiple angles. He’s best known for his work in cellular pathology, and he described diseases from leukemia to spina bifida. His work describing so many maladies might have helped him make the wrong call when it came to the neanderthal skeleton. Those who accepted that it was a real fossil, naturally had to answer the question of what exactly it was, if it wasn’t an early version of humanity. August Mayer, a paleontologist, had come up with an interesting alternate theory.

The fossils, Mayer claimed, were the remains of a Cossack, one of the many who had come into Germany in the very early 1800s. This one was old, and had spent most of his life on horseback. This, along with rickets due to poor nutrition and a touch of arthritis, accounted for the strange shape of the bones. As for the skull, the cossack had probably died of a cranial injury. In his confusion he had crawled into a cave. And if he subsequently got covered with a great deal of dirt, well, caves are muddy.

Virchow took a look at the remains and agreed with Mayer. Virchow’s fame gave what would otherwise be an outlandish theory legs. Virchow was not a disinterested source. A critic of Charles Darwin, he didn’t believe in evolution and certainly didn’t believe in early humans. His disbelief was ideologically driven, but not by the ideology we tend to see today. Virchow was witnessing the beginning of what came to be known as “social darwinism,” and he didn’t care for it. He wanted to help people in bad situations, not dismiss them as the expendable losers of society. Unfortunately for him, he did allow his ethical concerns to make him pick the wrong factual side.

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Neanderthals and humans interbred in Europe for 5,400 years Jul 15, 2015 1:54:23 GMT

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Post by Admin on Jul 15, 2015 1:54:23 GMT

Anatomically modern humans overlapped and mated with Neandertals such that non-African humans inherit ~1 to 3% of their genomes from Neandertal ancestors. We identified Neandertal lineages that persist in the DNA of modern humans, in whole-genome sequences from 379 European and 286 East Asian individuals, recovering more than 15 gigabases of introgressed sequence that spans ~20% of the Neandertal genome (false discovery rate = 5%). Analyses of surviving archaic lineages suggest that there were fitness costs to hybridization, admixture occurred both before and after divergence of non-African modern humans, and Neandertals were a source of adaptive variation for loci involved in skin phenotypes. Our results provide a new avenue for paleogenomics studies, allowing substantial amounts of population-level DNA sequence information to be obtained from extinct groups, even in the absence of fossilized remains.

Fig. 1. Recovering Neandertal lineages from the DNA of modern humans

At FDR = 5%, we identified more than 15 Gb of introgressed sequence across all individuals, spanning ~20% (600 Mb) of the Neandertal genome (Fig. 1E and table S9). Of the 600 Mb of distinct sequence, ~25% (149 Mb) was shared between Europeans and East Asians. On average, we found 23 Mb of introgressed sequence per individual (Fig. 1F), with East Asian individuals inheriting 21% more Neandertal sequence than Europeans. Within subpopulations, we found small but statistically significant variation in the amount of introgressed sequence among Europeans (Kruskal-Wallis rank sum test, P = 4.2 × 10–12), but not among East Asians (P = 0.43).

Fig. 4. Signatures of adaptive introgression.

We next leveraged the catalog of introgressed sequences in East Asians and Europeans to refine admixture models and infer parameters of gene flow between modern humans and Neandertals (figs. S14 and S15). Specifically, with the use of an approximate Bayesian computation framework (10), we statistically tested a model with a single pulse of introgression into the common ancestor of Europeans and East Asians (3), as well as a second model with gene flow both in the common ancestor and a second, smaller pulse into East Asians shortly after the two populations split (Fig. 3A). Consistent with recent inferences (5, 9), observed patterns of introgression were incompatible with a one-pulse model (Fig. 3B), suggesting that gene flow between Neandertals and humans occurred multiple times. Although we varied many parameters of each model (10) (fig. S14), only the ratio of ancestral effective population size between Europeans and East Asians (Ne EUR/Ne ASN) and the relative amount of introgression between the second and first pulse (m2/m1) had appreciable effects on model fit (Fig. 3B). We estimate that Ne EUR/Ne ASN is 1.29 [95% confidence interval (CI) of 1.15 to 1.57] and that East Asians received 20.2% (95% CI of 13.4 to 27.1%) more Neandertal sequence in the second pulse (10). We note that additional unexplored models may provide a better fit to the data, and refining demographic models of hominin evolution is an important area for future work.

This study shows that the fragmented remnants of the Neandertal genome carried in the DNA of modern humans can be robustly identified, allowing, in aggregate, substantial amounts of Neandertal sequence to be recovered. In principle, our approach can be used in the absence of an archaic reference sequence, potentially allowing the discovery and characterization of previously unknown hominins that interbred with modern humans (22–24). This fossil-free paradigm of sequencing archaic genomes holds considerable promise for revealing insights into hominin evolution, the population genetics characteristics of archaic hominins, how introgression has influenced extant patterns of human genomic diversity, and narrowing the search for genetic changes that endow distinctly human phenotypes.

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Neanderthals and humans interbred in Europe for 5,400 years Jul 23, 2015 2:05:20 GMT

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Post by Admin on Jul 23, 2015 2:05:20 GMT

The most comprehensive dataset ever assembled on our early human ancestors provides evidence that the first humans emerged in South Africa, and that the first humans to migrate out of Africa came from a small-bodied species such as Homo habilis, aka "Handy Man." The theory is a complete shake-up of the human family tree, since it has long been theorized that a relatively tall, muscular human, Homo erectus (Upright Man), was the first to leave Africa for Asia and Europe.

Traditionally, Handy Man "was viewed as a little human, with a relatively big brain, bipedalism, and tool-making forming part of the picture," said Mark Collard, a professor at Simon Fraser University's Human Evolutionary Studies Program and Department of Archaeology, and senior author of the study in Proceedings of the Royal Society B.

Collard, however, added that a revised view of Handy Man is that this human was much more ape-like than us, combining walking on two legs with frequent climbing. Since the scrappy individuals were thought to have been a favorite snack of non-human predators at the time, one can imagine that Handy Man had to be handy with his feet as well when he was threatened.

For the study, Collard and his team compared alternative human evolutionary trees, seeing how well they fit the newly constructed dataset. The output from each, he explained, was a statistic representing one of the following: it was consistent with the dataset, it was not consistent and therefore could be rejected, or it fell somewhere in the middle. The study rejected the theory that Homo floresiensis individuals, "Hobbit Humans," were simply deformed members of our own species. The data instead shows that these tiny residents of the Island of Flores, Indonesia, did indeed belong to a unique species. Collard and his team suspect that the hobbits descended from a small-bodied early Homo species, such as Handy Man.

As for Neanderthals, "We're pretty sure that Neanderthals are an exclusively Eurasian species; there is no evidence for them in Africa," he shared. The species that gave rise to Neanderthals remains a mystery for now. This puzzlement about them, and other Middle Pleistocene humans, is referred to as "the muddle in the middle," Collard said. Somewhat less confusing is the evidence on where the first humans likely emerged. The researchers plugged in information concerning the two-million-year-old human ancestor Australopithecus sediba, to help make that determination. "The fact that Australopithecus sediba groups with Homo is consistent with the idea that the earliest known representative of the genus Homo originated in South Africa," Collard said.