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 5, 2016 22:46:32 GMT

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Post by Admin on Jun 5, 2016 22:46:32 GMT

A team of researchers from Europe, Russia and the US analysed width and length of arm, leg and pelvic bones from two neonate Neanderthal (Homo neanderthalensis) skeletons: one from Mezmaiskaya in Russia and another from Le Moustier in France. They then compared the measurements to recent skeletons of African and European-American babies of a comparable age.

Compared to modern human skeletons, the Neanderthals had large hips relative to thigh-bone length, suggesting they were stocky from birth. The Mezmaiskaya skeleton also had a longer pubis and wider long bones than modern baby skeletons.

In short, the baby Neanderthals looked like smaller versions of adults, the researchers write: "Neanderthals largely look like Neanderthals, regardless of age."

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Neanderthals and humans interbred in Europe for 5,400 years Jun 6, 2016 22:52:46 GMT

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Post by Admin on Jun 6, 2016 22:52:46 GMT

The Neanderthal genome included harmful mutations that made the hominids around 40% less reproductively fit than modern humans, according to estimates published in the latest issue of the journal Genetics. Non-African humans inherited some of this genetic burden when they interbred with Neanderthals, though much of it has been lost over time. The results suggest that these harmful gene variants continue to reduce the fitness of some populations today. The study also has implications for management of endangered species.

Harris and her colleague Rasmus Nielsen (University of California, Berkeley / University of Copenhagen) hypothesized that the force in question was natural selection. In small populations, like the Neanderthals', natural selection is less effective and chance has an outsized influence. This allows weakly harmful mutations to persist, rather than being weeded out over the generations. But once such mutations are introduced back into a larger population, such as modern humans, they would be exposed to the surveillance of natural selection and eventually lost.

To quantify this effect, Harris and Nielsen used computer programs to simulate mutation accumulation during Neanderthal evolution and to estimate how humans were affected by the influx of neanderthal genetic variants. The simulations incorporated data on the mutation rates, genome properties, and population dynamics of hominids.

The results suggest that Neanderthals carried many mutations with mild, but harmful effects. The combined effect of these weak mutations would have made Neanderthals at least 40% less fit than humans in evolutionary terms--that is, they were 40% less likely to reproduce and pass on their genes to the next generation.

Harris and Nielsen's simulations also suggest that humans and Neanderthals mixed much more freely than originally thought. Today, Neanderthal sequences make up approximately 2% of the genome in people from non-African populations. But Harris and Nielsen estimate that at the time of interbreeding, closer to 10% of the human migrants' genome would have been Neanderthal. Because there were around ten times more humans than Neanderthals, this number is consistent with the two groups acting as as single population that interbred at random. Recent DNA evidence has confirmed that the Neanderthal contribution to Eurasian genomes was higher in the past.

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Neanderthals and humans interbred in Europe for 5,400 years Jun 10, 2016 22:40:14 GMT

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Post by Admin on Jun 10, 2016 22:40:14 GMT

Deep inside Bruniquel Cave, in the Tarn et Garonne region of southwestern France, a set of human-made structures[1] 336 meters from the entrance was recently dated as being approximately 176,500 years old. This discovery indicates that humans began occupying caves much earlier than previously thought: until now the oldest formally proven cave use dated back only 38,000 years (Chauvet). It also ranks the Bruniquel structures among the very first in human history. In addition, traces of fire show that the early Neanderthals, well before Homo sapiens, knew how to use fire to circulate in enclosed spaces far from daylight. The research, reported in the 25 May 2016 issue of Nature, was conducted by an international team including Jacques Jaubert from the University of Bordeaux, Sophie Verheyden from the Royal Belgian Institute of Natural Sciences (RBINS) and Dominique Genty of the CNRS, with logistical support from the Société Spéléo-Archéologique de Caussade under president Michel Soulier and the backing of the French Ministry of Culture and Communication.

Bruniquel Cave, an extraordinary find

Bruniquel Cave was discovered in 1990 on a site overlooking the Aveyron Valley. The team of speleologists in charge of its management has kept the site in pristine condition, preserving its numerous natural formations (an underground lake, calcite rafts, translucent flowstone, concretions of all types…), intact floors containing numerous bone remains and dozens of bear hibernation hollows[2] with impressive claw marks. But most importantly, the cave contains original structures made up of about 400 stalagmites or sections of stalagmites, gathered and arranged in more or less circular formations. These circles show signs of fire use: calcite reddened or blackened by soot and fractured by heat, as well as burnt matter including bone remnants. In 1995, a first team of speleologists and researchers[3] used carbon 14 to date a burnt bone at 47,600 years (the oldest possible date using that technique), but no further dating was carried out at that time.

In 2013 a team of researchers, with the backing of the DRAC Midi Pyrénées regional archaeological department, launched a new program of studies and analyses. In addition to a 3D survey of the stalagmite structures and an inventory of their constituent elements, a magnetic study was used to reveal anomalies caused by heat, making it possible to map the burnt remnants found in this part of the cave. It seems most plausible that these fires were simply used as light sources.

Since no other stalagmite structure of this scale has yet been discovered, the team developed a new concept to designate these carefully arranged pieces of stalagmites: "speleofacts." An inventory of the cave's 400 speleofacts reveals a total of 112 meters of stalagmites broken into well-calibrated pieces, weighing an estimated 2.2 metric tons. The components of the structures are aligned, juxtaposed and superimposed (in two, three and even four layers), with props around the outside, apparently to hold them in place, and filler pieces. Marks left by the wrenching of stalagmites from the cave floor to make the structures have been identified nearby.

No remains were found in the cave floors that could help date the installation: a thick crust of calcite has coated the structures, sealing them in place and concealing the original floor. For this reason, the researchers, with the help of colleagues from the University of Xi'an (China) and the University of Minnesota (US), used a method called uranium series dating (U-Th), based on the radioactive properties of uranium, trace amounts of which are omnipresent in the environment. When stalagmites are formed, uranium is present in the calcite. Over time it breaks down into other elements, including thorium (Th). The age of a stalagmite can therefore be determined by measuring the thorium and remaining uranium in the calcite.

The Neanderthals made these structures by breaking stalagmites and rearranging the pieces. After the site was abandoned, new layers of calcite, including new stalagmite growth, formed on the human-made structures. By dating the end of the growth of the stalagmites used in the structures and the beginning of the regrowth sealing those same structures, the researchers have estimated the age of the installation at 176,500 years, ± 2,000 years. Additional samples, in particular of the calcite covering a burnt bone, confirmed this surprising result.

Were the first Neanderthals explorers and builders?

The very existence of these structures, virtually unique in the annals of archaeology, was already an astonishing discovery. In Prehistory, it wasn't until the beginning of the recent Paleolithic[4] in Europe, plus some isolated cases in Southeast Asia and Australia, that man was known to make regular incursions into the underground world, beyond the reach of sunlight. The proof is nearly always drawings, engravings and paintings, like those found in the caves of Chauvet (-36,000 years), Lascaux (-22,000 to -20,000 years), Altamira in Spain and Niaux (-18,000 to -15,000 years for both sites) and, more rarely, burial sites (Cussac Cave in France's Dordogne region: -28,500 years). But the Bruniquel stalagmite structures were built long before modern humans arrived in Europe (-40,000 years). Their creators must therefore have been the first Neanderthals[5] so far presumed by the scientific community not to have ventured far underground, nor to have mastered such sophisticated use of lighting and fire, let alone to have built such elaborate constructions.

New questions about the Neanderthals

We now know that, some 140 millennia before the arrival of modern man, Europe's first Neanderthals were occupying deep caves, building complex structures and maintaining fires in them. The Bruniquel structures are of particular interest due to their distance from the mouth of the cave, which is thought to be the same now as in the days of the Neanderthals. The researchers also wonder what the function of these installations, so far from daylight, could have been. Eliminating the unlikely hypothesis of shelter, given the structures' distance from the entrance, was it to find materials of now-unknown utility? Could it have been for "technical" purposes, such as water storage? Or for the observance of religious or other rites? In any case, the researchers confirm that the Neanderthals had to have an advanced social organization to build such constructions. Further studies will attempt to explain their function, which for the moment remains the biggest mystery surrounding Bruniquel Cave.

[1] Comprising approximately 400 stalagmites, or elements from the stalagmitic floor, most of them cut into sections, arranged in two more or less circular shapes and four other accumulations.

[2] Places where bears settle in for the winter, in order to hibernate under stable thermal conditions.

[3] Led by François Rouzaud, at the time chief heritage curator of the DRAC Midi Pyrénées, and Michel Soulier, president of the Société Spéléo-Archéologique de Caussade.

[4] From 45,000 to 12,000 years ago.

[5] The known Neanderthal fossils are between 40,000 and 250,000 years old.

Last Edit: Apr 13, 2018 5:08:18 GMT by Admin

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Neanderthals and humans interbred in Europe for 5,400 years Jun 20, 2016 22:43:33 GMT

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Post by Admin on Jun 20, 2016 22:43:33 GMT

The verdict of experts from the London Natural History Museum has revived the theory that a tooth discovered in Għar Dalam in 1917 may prove Neanderthals once roamed the island. The claim is not new. It was made in the 1920s by two British anthropologists, but four decades later the theory no longer had credence.

“Well, the presence of Neanderthals pushes that back some 30,000 years. It’s a complete game changer,” he told the Sunday Times of Malta yesterday. Dr Mifsud believes features recently identified as being “exclusively Neanderthal” by international experts are present in at least one molar found during the dig in Għar Dalam in 1917.

In a recently published book entitled Dossier Malta – Neanderthal Dr Mifsud lays out his study of the crowns of these teeth using the same principles adopted by world leaders in the field of geometric morphometrics – the quantitative analysis of shapes and sizes in nature.

By examining the grooves and edges of the molars, he discovered features on their surfaces, including a particular cusp which formed a kind of ‘dental fingerprint’. According to the experts, this is “undeniably” Neanderthal. Dr Mifsud did not stop there. He wasted little time in contacting world leaders in several fields, including experts from the Natural History Museum in London, all of whom confirmed his findings.

AT a meeting of the Royal Anthropological Institute on March 4, the president, Prof. C. G. Seligman, in the chair, a paper by Sir Arthur Keith on “The Discovery of Neanderthal Man in Malta, with an account of the Survey of the Cave in which the evidence was found (Ghar Dalam), by Mr. George Sinclair,” was presented by Dr. A. Burkitt, of the University of Sydney, in the absence of the author The discovery was made in 1917 by Mr. G. Despott, curator of the Malta Natural History Museum, who in digging a trench across the deposits on the floor oof Ghar Dalam found two human teeth of a remarkable character. They lay in the second stratum of the cave-a deposit of red cave earth, which varies in depth from 6 to 8 feet. Over the cave earth is a superficial stratum varying from ij to 2-| feet in depth and of neolithic date, while under the cave “arth is the third stratum, a bone breccia 3 feet in thickness, made up chiefly of rolled fragments of fossil bones belonging to two species of hippopotamus and three species of extinct elephants. The two teeth were found i| feet and 2j feet deep in the red cave earth with remains of stag, elephant (E. Mnaidrensis), and hippopotamus (H. pentlandi). These bones and the teeth were in the same state of fossilisation. At the same levels and mingled with the above were found chards of neolithic pottery, teeth, and also other remains of neolithic man. Men of the neolithic period and of later dates had lived in the cave and wrought some degree of confusion in the upper levels of the cave earth. In spite of extensive excavations carried out under the auspices of the British Association, no trace of the culture of palaeolithic man has been found-neither of the Mousterian period, which is that of Neanderthal man, nor of the later Aurignacian period. All that can be assigned with certainty to palaeolithic man are the two molar teeth.

Nature 113, 405-405 (15 March 1924) | doi:10.1038/113405a0

Last Edit: Apr 13, 2018 5:08:54 GMT by Admin

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Neanderthals and humans interbred in Europe for 5,400 years Jun 22, 2016 22:46:10 GMT

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Post by Admin on Jun 22, 2016 22:46:10 GMT

Fig. 1.

Adult European Americans and African Americans differ, on average, in body proportions, with European Americans having a wider trunk relative to limb length and relatively shorter distal limb segments (22, 23). These contrasts are much the same, although less extreme, as those between high- and low-latitude human groups (24, 25), and result from the geographic ancestries of European Americans and African Americans [Bergmann’s (26) and Allen’s (27) “rules”]. Similar proportional differences are already detectable in our fetal/infant sample (Fig. 1), which is consistent with other studies of subadult body proportions (28, 29). European Americans tend to have a wider and a longer ilium relative to femur length (Fig. 1 A and B), a shorter radius relative to humerus length (Fig. 1C), and a shorter tibia relative to femur length (Fig. 1D). Consistent with the “cold-adapted” body proportions of adult Neandertals (24, 30, 31), both Mezmaiskaya 1 and Le Moustier 2 have a very large ilium relative to femur length (Fig. 1 A and B), and Mezmaiskaya 1 has short distal-to-proximal limb lengths (Fig. 1 C and D; the results for tibia–femur proportions are less conclusive than for radius–humerus proportions because, although Mezmaiskaya 1 plots just below the European-American curve, the curves are minimally separated in this part of the graph). However, unexpectedly, Le Moustier 2 has a long radius relative to humerus length (Fig. 1C).

Fig. 3.

Adult European Americans and African Americans differ, on average, in the shapes of their long bones, with European Americans having thicker shafts and larger articulations relative to shaft length (23, 36). In dry-bone samples of young individuals, it is not possible to compare articulation size to shaft length, because the articulations are mostly or completely cartilaginous. However, it is possible to compare the diaphysis end (i.e., metaphysis) size, which should be related to articulation size, to diaphysis length. Our fetal/infant sample does not show a uniform contrast between European Americans and African Americans in end size to length (Fig. 3). For the humerus (Fig. 3A) and femur (Fig. 3C), African Americans tend to have larger ends relative to length; for the tibia (Fig. 3D), European Americans tend to have larger ends relative to length; and for the radius (Fig. 3B), there is no consistent difference across size (i.e., age) in end size relative to length. Adult Neandertals have thick shafts and large articulations relative to shaft length (36⇓–38), and Mezmaiskaya 1 and Le Moustier 2 may anticipate this feature of adult Neandertals by having long bone diaphyses with very large ends relative to length (Fig. 3).

Fig. 4.

Principal components (PCs) of residuals from the all-recent-human regressions provide a multivariate synthesis of the bivariate analyses (Fig. 4). PC1 encompasses 37% of the variance, and it mainly reflects differences in ilium size relative to femur length and long bone diaphysis end to length dimensions; PC2 encompasses 23% of the variance, and it mainly reflects differences in distal to proximal limb lengths; and PC3 encompasses 19% of the variance, and it mainly reflects differences in pubis length relative to ilium size, ilium length relative to femur length, and radius length relative to humerus length (Table S5). Mezmaiskaya 1 has a highly positive score on PC1 (Fig. 4A), which reflects its large ilium relative to femur length and long bone diaphyses with large ends relative to lengths. Differences between African Americans and European Americans along PC2 and PC3 appear to reflect differences in body proportions, and Mezmaiskaya 1 plots within but near the edge of the European-American convex hull (Fig. 4B).

If we consider that evolutionary changes are a more likely explanation than fetal environment for skeletal differences between Neandertals and modern humans, climatic adaptation is the best-supported explanation for many aspects of Neandertal postcranial form because Neandertals have body proportions close to present-day humans with ancestry in cold climates (24, 30, 31), it appears that multiple generations are necessary for appreciable changes in body proportions (i.e., an evolutionary timescale is needed) (24, 25), a wide variety of taxa exhibit similar ecological relationships (47⇓–49), and laboratory experiments on human subjects demonstrate that body proportions influence heat loss (50) [see also Churchill (51)]. Recent research, however, has cast some doubt on this explanation. Because the modern human expansion from Africa that gave rise to recent human groups had a substantial south-to-north component, differences among recent human groups in body proportions could have more to do with population history than climatic adaptation (52⇓–54). Additionally, a wide body may have been the ancestral condition for Homo (7, 55⇓–57), even though the earliest members of our genus presumably lived in warm climates. Consequently, although it remains likely that many postcranial differences between Neandertals and modern humans stem from contrasts in body proportions (21, 36, 38, 58), further research will be necessary to establish whether climate played an important role in shaping these differences in body proportions.

Timothy D. Weaver, doi: 10.1073/pnas.1523677113