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Neanderthal assimilation and admixture in all of us? Interbreeding study

You may wish to check out a new analysis appearing online since February 13, 2014. of the archaeological records of Neanderthals and their modern human contemporaries has found that complex interbreeding and assimilation may have been responsible for Neanderthal disappearance 40,000 years ago, in contrast to many current theories, according to results of a study, "Neanderthal Demise: An Archaeological Analysis of the Modern Human Superiority Complex," published April 30, 2014, in the open access journal PLOS ONE by Paola Villa from the University of Colorado Museum and Wil Roebroeks from Leiden University in the Netherlands. You also may wish to check out the abstract of a recent study, "Neandertal Admixture in Eurasia Confirmed by Maximum-Likelihood Analysis of Three Genomes," appearing online since February 13, 2014 in the journal Genetics.

Neanderthal assimilation and admixture in all of us?
Photo by Photo by Giorgio Cosulich/Getty Images

Complex and drawn-out processes of interbreeding and assimilation may have been responsible for the disappearance of the specific Neanderthal morphology from the fossil record. A new study questions Neanderthal inferiority to early modern humans and explains that the Neanderthal demise may be the result of interbreeding, assimilation, not early modern human superiority. They are us, and we are them, that is, a part of them genetically speaking, admixed, interbred, assimilated, and absorbed into the autosomal DNA so that the keratin in hair and nails is what shows up in current times and some genes that affect immunity or other health issues.

The researchers show in the new study that the Neanderthal archaeological record was not different enough to explain their demise in terms of inferiority in archaeologically visible domains.

So, if Neanderthals were not technologically and cognitively “disadvantaged,” how do the researchers explain that they did not survive? They look at the genetic studies to see how, when, and where Neanderthals and Homo Sapiens admixed. Neanderthals thrived in Eurasia for more than 300,000 years but vanished around 40,000 years ago, around the same time that modern humans entered Europe. There's a study that reports genetic findings where Neanderthals and Homo Sapiens admixed in Eurasia.

Archaeologists have developed many theories to explain their disappearance, and many of these suggest that modern-day humans were superior in a wide range of ways, including weaponry and subsistence strategies, according to the April 30, 2014 news release, "Study questions Neanderthal inferiority to early modern humans." This superiority may have eventually led to the demise of Neanderthals. However, new evidence, including genetic data, suggest that differences between Neanderthals and modern humans in Africa may not be so clear as previously thought.

Differences between Neanderthals and modern humans in Africa may not be so clear as previously thought, says the new research

In this latest study, scientists systematically tested the strength of some of the archaeologically derived explanations for Neanderthal extinction, such as the Neanderthals' supposed lack of complex language, inferior capacity for innovation, inferior hunting ability, and smaller social networks, as well as other environmental explanations, including harsh climate or volcanic eruptions that occurred at the time of their decline. But what if there are other explanations?

If the Neanderthal record is compared to that of African Middle Stone Age human contemporaries, instead of the modern humans that succeeded them, the differences between them and humans in their capacities, like weaponry, subsistence, and use of symbols are too small to explain their demise in terms of cognitive or behavioral inferiority. Instead, the authors argue, genetic data recently obtained from Neanderthal skeletal remains suggest that complex and drawn-out processes of interbreeding and assimilation may have been responsible for the disappearance of the specific Neanderthal morphology from the fossil record.

What cognitive gap between them and us?

The study explains that "after 40,000 years and 2000 generations the Neanderthal fraction in non-African modern human genomes still constitutes a substantial legacy from these ancient hominins who differed from contemporary AMHs in both geno- and phenotypes but whose archeological record was not different enough to support the purported cognitive “gap” between them and their contemporary modern humans."

The study is open access. You can check out, Neanderthal Demise: An Archaeological Analysis of the Modern Human Superiority Complex," published April 30, 2014, in the open access journal PLOS ONE by Paola Villa from the University of Colorado Museum and Wil Roebroeks from Leiden University in the Netherlands. Authors of the study are Villa P, and Roebroeks W. Research by Paola Villa was funded by the National Science Foundation grant BCS 1118143. Both Paola Villa and Wil Roebroeks were supported by the Netherlands Organization for Scientific Research (N.W.O, SP128-548). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors have declared that no competing interests exist.

Neanderthal health

If you're interested in the health of Neanderthals, they had teeth free from dental decay, regardless of what they ate. In fact, they didn't eat much other than meat or what sea food they could find along the shore without access to fishing equipment. But what they did know about was how to make toothpicks, according to a new study. Check out the October 17, 2013 news release, Neanderthals used toothpicks to alleviate the pain of diseases such as inflammation of the gums.

You can read the study's findings from scientists at the Universitat Autonoma de Barcelona in the open access journal, Plos One. Check out the study, "Toothpicking and Periodontal Disease in a Neanderthal Specimen from Cova Foradà Site (Valencia, Spain)." On the other hand, even with no decay, the Neanderthals' remains found showed they did have gum disease. An IPHES research done in collaboration with UAB, documents reveals the oldest case of palliative treatment of periodontal disease. This is another step to characterize the Neanderthals as a species with a wide range of adaptations to the environment and, even, resources in medicine.

Another study on Neanderthals published in the Journal of Quaternary Science shows a record of Neanderthal archaeology, thought to be long lost, that now has been re-discovered by NERC-funded scientists working in the Channel island of Jersey. Results of this study are from the Natural Environment Research Council, according to the October 17, 2013 news release, "Archaeologists rediscover the lost home of the last Neanderthals." That island of Jersey refers to the one in the British Isles, not New Jersey in the USA.

A record of Neanderthal archaeology, thought to be long lost, has been re-discovered by NERC-funded scientists working in the Channel island of Jersey. The study, published October 17, 2013 in the Journal of Quaternary Science reveals that a key archaeological site has preserved geological deposits which were thought to have been lost through excavation 100 years ago.

The discovery was made when the team undertook fieldwork to stabilize and investigate a portion of the La Cotte de St Brelade cave, on Jersey's south eastern coastline

A large portion of the site contains sediments dating to the last Ice Age, preserving 250,000 years of climate change and archaeological evidence. The site, which has produced more Neanderthal stone tools than the rest of the British Isles put together, contains the only known late Neanderthal remains from North West Europe. These offer archaeologists one of the most important records of Neanderthal behavior available.

"In terms of the volume of sediment, archaeological richness and depth of time, there is nothing else like it known in the British Isles. Given that we thought these deposits had been removed entirely by previous researchers, finding that so much still remains is as exciting as discovering a new site," says Dr Matt Pope of the Institute of Archaeology at University College London, who helped lead the research, according to the October 17, 2013 news release, "Archaeologists rediscover the lost home of the last Neanderthals."

The team dated sediments at the site using a technique called Optically Stimulated Luminesce, which measures the last time sand grains were exposed to sunlight. This was carried out at the Luminescence Dating Research Laboratory for Archaeology and the History of Art at Oxford University

The results showed that part of the sequence of sediments dates between 100,000 and 47,000 years old, indicating that Neanderthal teeth which were discovered at the site in 1910 were younger than previously thought, and probably belonged to one of the last Neanderthals to live in the region.

"The discovery that these deposits still exist and can be related to previously excavated deposits opens up a range of exciting possibilities," says Dr Martin Bates, University of Trinity St Davids, who is leading current fieldwork at the site, according to the October 17, 2013 news release, "Archaeologists rediscover the lost home of the last Neanderthals." The findings bring the large collections of stone tools, animal bone and the Neanderthal remains from the area under renewed study.

"Excavation in the future will provide us with the opportunity to subject the site to the wide range of approaches we use today in Palaeolithic archaeology and Quaternary science. For example we are hoping to be able to link our site with the broader Neanderthal landscapes through study of similarly aged deposits around the island and, through bathymetric survey, on the seabed," says Bates in the news release.

"We were sure from the outset that the deposits held some archaeological potential, but these dates indicate we have uncovered something exceptional," explains Pope in the news release. "We have a sequence of deposits which span the last 120,000 years still preserved at the site. Crucially, this covers the period in which Neanderthal populations apparently went 'extinct'."

It was during this period that Neanderthals appear to have been replaced by our own species - Homo sapiens

The NERC-funded work represented the first formal programme of scientific research to be focused on the site since the early 1980s. The site has since then been managed and preserved by the Société Jerisaise, the Jersey-based academic society involved in early investigation of the site and which continues to manage and protect the site through to the present day.

"For over a hundred years the Societe has tried to maintain the interest of the wider academic world in La Cotte, having realized its international importance from the beginning. We are delighted, therefore, that such a prestigious team is now studying the site, and, in addition, the wider Palaeolithic landscape of Jersey," says Neil Molyneux, president of the Société Jersiaise, according to the October 17, 2013 news release, "Archaeologists rediscover the lost home of the last Neanderthals."

The wider project, supported also by the Arts and Humanities Research Council and the Jersey Government will now continue to investigate the site and material excavated from it over the past 110 years

"Working with our partners to bring these rediscovered sediments under new analysis will allow us to bring the lives of the last Neanderthal groups to live in North West Europe into clearer focus," says Pope in the news release. "We may be able to use this evidence to better understand when Neanderthal populations disappeared form the region and whether they ever shared the landscape with the species which ultimately replaced them, us," he concludes in the news release. For more information, you may wish to see the Natural Environment Research Council site.

Denisovans made the journey to Australia, Melanesia, including Papua-New Guinea

Those cousins to Neanderthals, the Denisovans of Central Asia, also made it further east to Australia and New Guinea, says a new study published on October 18, 2013 in Science magazine You can check out the abstract of the study, "Did the Denisovans Cross Wallace's Line?" Or listen to the Podcast Interview.

According to an October 17, 2013 news release, "Mysterious ancient human crossed Wallace's Line." Scientists from the University of Adelaide in Australia have proposed that the most recently discovered ancient human relatives -- the Denisovans -- somehow managed to cross one of the world's most prominent marine barriers in Indonesia, and later interbred with modern humans moving through the area on the way to Australia and New Guinea.

Scientists have proposed that the most recently discovered ancient human relatives -- the Denisovans -- somehow managed to cross one of the world's most prominent marine barriers in Indonesia, and later interbred with modern humans moving through the area on the way to Australia and New Guinea

Three years ago the genetic analysis of a little finger bone from Denisova cave in the Altai Mountains in northern Asia led to a complete genome sequence of a new line of the human family tree -- the Denisovans. Since then, genetic evidence pointing to their hybridization with modern human populations has been detected, but only in Indigenous populations in Australia, New Guinea and surrounding areas, says the study.

The only question readers have is if the genes only have been detected in indigenous populations of Melanesia, how come some of the DNA testing companies give you your average 2.0 percentage of Denisovan genes if you're of European or Asian ancestry (or mixed with Asian or European and any other ancestry)? Although, on the other hand, the issue is still being researched. Most Europeans seem to come up a percentage of Neanderthal and a percentage of Denisovan on the DNA tests that give you your 'score' of autonomous DNA of Denisovan and/or Neanderthal.

Apparently, the Denisovans lived in the Altai and across Central Asia and mixed with Europeans and Asians as well as Melanesians, but at different percentage rates. And Neanderthals mixed with those who left Africa, such as Europeans, Asians, and Melanesians, but not with those who never left Africa for other parts of the world in prehistoric times, according to various research studies to date.

In contrast, Denisovan DNA appears to be absent or at very low levels in current populations on mainland Asia, even though this is where the fossil was found

Published October 18, 2013 in a Science opinion article, scientists Professor Alan Cooper of the University of Adelaide in Australia and Professor Chris Stringer of the Natural History Museum in the UK say that this pattern can be explained if the Denisovans had succeeded in crossing the famous Wallace's Line, one of the world's biggest biogeographic barriers which is formed by a powerful marine current along the east coast of Borneo. Wallace's Line marks the division between European and Asian mammals to the west from marsupial-dominated Australasia to the east.

"In mainland Asia, neither ancient human specimens, nor geographically isolated modern Indigenous populations have Denisovan DNA of any note, indicating that there has never been a genetic signal of Denisovan interbreeding in the area," says Professor Cooper, Director of the Australian Centre for Ancient DNA - University of Adelaide, according to the October 17, 2013 news release, Mysterious ancient human crossed Wallace's Line. "The only place where such a genetic signal exists appears to be in areas east of Wallace's Line and that is where we think interbreeding took place -- even though it means that the Denisovans must have somehow made that marine crossing."

Interbeeding may have taken place east of the Wallace Line, according to the study

"The recent discovery of another enigmatic ancient human species Homo floresiensis, the so-called Hobbits, in Flores, Indonesia, confirms that the diversity of archaic human relatives in this area was much higher than we'd thought," says Professor Stringer, Research Leader in Human Origins, Natural History Museum, in London, according to the news release. "The morphology of the Hobbits shows they are different from the Denisovans, meaning we now have at least two, and potentially more, unexpected groups in the area.

"The conclusions we've drawn are very important for our knowledge of early human evolution and culture. Knowing that the Denisovans spread beyond this significant sea barrier opens up all sorts of questions about the behaviors and capabilities of this group, and how far they could have spread."

"The key questions now are where and when the ancestors of current humans, who were on their way to colonise New Guinea and Australia around 50,000 years ago, met and interacted with the Denisovans," says Professor Cooper in the news release. "Intriguingly, the genetic data suggest that male Denisovans interbred with modern human females, indicating the potential nature of the interactions as small numbers of modern humans first crossed Wallace's Line and entered Denisovan territory."

Interestingly, in Europe, other scientists looking at Neanderthals, a cousin of Denisovans also found that male Neanderthals interbred with human females, probably in the Middle East, before the admixed populations kept moving toward Europe and Asia. See, "First Love Child of Human, Neanderthal Found: Discovery News." That article explains, "The skeletal remains of an individual living in northern Italy 40,000-30,000 years ago are believed to be that of a human/Neanderthal hybrid, according to a paper in PLoS ONE."

Scientists still need to do further research on that theory about the possible hybrid found in Italy

If the theory turns out to be correct, it's the first fossil found to date that shows actual evidence that humans and Neanderthals admixed. In the past few years scientists found that Europeans and Asians carry anywhere from 1 to 4 percent Neanderthal genes. Many Europeans who have their DNA tested come out with 2.7% Neanderthal or similar percentages.

For example, the National Genographic project and other DNA testing firms give you your percentage of Neanderthal and Denisovan genes. With the study on the hybrid Neanderthal and Homo Sapien skull, the study looks at the person's jaw. The skull was found buried in a rock-shelter called Riparo di Mezzena in the Monti Lessini region of Italy.

Both Neanderthals and modern humans inhabited Europe at the time. Now the question remains whether the Neanderthals were interbreeding with Homo Sapien women in exchange for being given food or tools? Did the women choose the Neanderthal males? Or were the Home Sapien women taken by capture? Then again, the fittest males don't always get the girl by her choice. See, "Faint heart sometimes wins fair lady." In prehistoric times, getting food was a priority.

Depending on what part of the world from which your ancestors arrived, humans not only interbred with Neanderthals, they also mated with Denisovans, according to several new studies

You may wish to see the site, "New DNA analysis shows ancient humans interbred with Denisovans." Denisovans lived in the large area going from Siberia to East Asia. Neanderthals lived in the Middle East and Europe. And both mixed with Homo Sapiens, depending on where any of your prehistoric ancestors lived. In 2012 the entire genome of Denisovans were mapped. See, "Denisovans, an ancient human group, have genome mapped." And Neanderthals also have had their genome mapped in March 2013, making it scientifically possible to clone them back, if anyone ever tries. See, "Entire Neanderthal Genome Mapped For The First Time | Fast."

Asia was settled in multiple waves by different peoples

A recent DNA study suggests Asia was settled in multiple waves of migration from undifferentiated peoples that didn't resemble the way modern Chinese or Indonesian people look in current times, reports a September 22, 2011 news release by by Debra Ruder, "DNA study suggests Asia was settled in multiple waves of migration." Analysis reveals archaic Denisovans lived from Siberia to Southeast Asia. An international team of researchers studying DNA patterns from modern and archaic humans has uncovered new clues about the movement and intermixing of populations more than 40,000 years ago in Asia.

One archaeogentics study showed a Denisovan girl found had brown hair, brown eyes, and brown skin. See, "Genome of Mysterious Extinct Human Reveals Brown-Eyed Girl." People have changed a lot genetically in the past 30,000 years. The scientists in one archeological and genetic project discovered about 100,000 recent changes in our genome that occurred after the split from the Denisovans.

A number of these changes influence genes linked with brain function and nervous system development, leading to speculation that we may think differently from the Denisovans. Other changes are linked with the skin, eyes and teeth. See, "Genome of ancient Denisovans may help clarify human evolution."

In another study, using state-of-the-art genome analysis methods, scientists from Harvard Medical School and the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have found that Denisovans—a recently identified group of archaic humans whose DNA was extracted last year from a finger bone excavated in Siberia—contributed DNA not just to present-day New Guineans, but also to aboriginal Australian and Philippine populations.

The study demonstrates that contrary to the findings of the largest previous genetic studies, modern humans settled Asia in more than one migration

According to David Reich, a professor of genetics at Harvard Medical School, "Denisova DNA is like a medical imaging dye that traces a person's blood vessels. It is so recognizable that you can detect even a little bit of it in one individual. In a similar way, we were able to trace Denisova DNA in the migrations of people. This shows the power of sequencing ancient DNA as a tool for understanding human history."

The patterns the researchers found can only be explained by at least two waves of human migration: the first giving rise to the aboriginal populations that currently live in Southeast Asia and Oceania, and later migrations giving rise to relatives of East Asians who now are the primary population of Southeast Asia.

The study also provides new insights about where the ancient Denisovans lived

According to Mark Stoneking, a professor at the Max Planck Institute who is senior author of the paper, Denisovans must have inhabited an extraordinarily large ecological and geographic range, from Siberia to tropical Southeast Asia. "The fact that Denisovan DNA is present in some aboriginal populations of Southeast Asia but not in others shows that there was a checkerboard of populations with and without Denisova material more than 44,000 years ago," he said. "The presence of Denisovan genetic material in some but not all the groups there can most easily be explained if Denisovans lived in Southeast Asia itself."

The findings appear on September 22, 2011 in the The American Journal of Human Genetics - Cell. This research builds on previous work by Reich and colleagues at the Max Planck Institute, in which they analyzed an ancient pinky bone uncovered by Russian archaeologists in the Siberian Denisova Cave in 2008. The Max Planck Institute team led by Svante Pääbo sequenced the bone's nuclear genome, and Reich led the population genetic analysis using algorithms that he and colleagues developed.

Reporting December 2010 in Nature, the team identified Denisovans as a distinct group of archaic humans (hominins) that lived more than 30,000 years ago and contributed genes to present-day New Guineans. They concluded that Denisovans were neither Neandertals nor early modern humans, though they shared a common ancestry. This paper helped fill in some empty pieces in the evolutionary puzzle that began after early humans left Africa and reinforces the view that humans have intermixed throughout history.

Genetic footprints

The new study was initiated by Stoneking, an expert on genetic variation in Southeast Asia and Oceania who has assembled diverse samples from that region. The study takes a closer look at the Denisovans' genetic footprint. The researchers analyzed DNA from dozens of present-day populations in Southeast Asia and Oceania, including Borneo, Fiji, Indonesia, Malaysia, Australia, the Philippines, Papua New Guinea and Polynesia. Some of the data already existed, and some were newly collected for the study.

Their analysis shows that, in addition to New Guineans, Denisovans contributed genetic material to Australian aborigines, a Philippine "Negrito" group called Mamanwa, and several other populations in eastern Southeast Asia and Oceania. However, groups in the west or northwest, including other Negrito groups such as the Onge in the Andaman Islands and the Jehai in Malaysia, as well as mainland East Asians, did not interbreed with Denisovans.

The researchers concluded that:

  • Denisovans interbred with modern humans in Southeast Asia at least 44,000 years ago before the time of the separation of the Australians and New Guineans.
  • Southeast Asia was first colonized by modern humans unrelated to present-day Chinese and Indonesians, and that these and other East Asians arrived in later migrations. This "southern route" hypothesis has previously been supported by archaeological evidence, but has never had strong genetic support.

Investigators from the Broad Institute of MIT and Harvard, from Germany, India, Taiwan, Japan, Malaysia, and The Netherlands also contributed. This study was funded by the Max Planck Society and the National Science Foundation HOMINID program. For more information, check out the site, "Human Origins (HOMINID) - National Science Foundation."

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