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The best explanation is that the Denisovans interbred with an unidentified species, and picked up some of their DNA. Or as Reich puts it: "Denisovans harbour ancestry from an unknown archaic population, unrelated to Neanderthals."
The data looks convincing, says geneticist Johannes Krause of the University of Tübingen in Germany. "There's a very strong signal, difficult to question."
Krause is one of several geneticists who have studied the Denisovan genome and wondered if....
“We have very clear evidence that this version of the gene came from Denisovans,” a mysterious human relative that went extinct 40,000-50,000 years ago, around the same time as the more well-known Neanderthals, under pressure from modern humans, said principal author Rasmus Nielsen, UC Berkeley professor of integrative biology. “This shows very clearly and directly that humans evolved and adapted to new environments by getting their genes from another species.”
"We find no trace of Denisovan genetic material in mainland Eurasia, including in mainland Southeast Asia, to the limits of our resolution," says study co-author David Reich of Harvard Medical School. "However, it's clear that Denisovan genetic material has contributed 3 percent to 5 percent of the genomes of people in Australia and New Guinea and aboriginal people from the Philippines and some of the island nearby."
originally posted by: Kratos40
a reply to: SLAYER69
Hey Slayer,
That illustration is on point when I read this article in the New York Times yesterday. I immediately remembered about your thread and posts about human migration across the world.
The human family is truely a gnarled bush of evolution. With more genetic information, we may elucidate the origins of the Kennewick Man mystery.
Since Gobekli Tepe has been slowly uncovered, I wonder if human "culture" goes back even further with different extinct human cousins.
As first first science officer Spock would have said "Fascinating".
However, the new evidence shows that these people did not arrive in an empty wilderness. Stone tools and charcoal from the site in Brazil show evidence of human habitation as long ago as 50,000 years.
The site is at Serra Da Capivara in remote northeast Brazil. This area is now inhabited by the descendants of European settlers and African slaves who arrived just 500 years ago.
But cave paintings found here provided the first clue to the existence of a much older people...
To make the link between the Denisovans and indigenous Australians, the study looked at two Aboriginal populations, one of which was from the Northern Territory. The researchers concluded that Denisovans interbred with modern humans in South-East Asia 44,000 years ago, before Australia separated from Papua New Guinea.
"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," say the scientists behind the research in a summary of the findings.
"The study also confirms controversial claims that the ancestors of all living Eurasians interbred with the Neandertals, while past Asians/Oceanians also mated with the mysterious ancient humans from Denisova cave[s] in Siberia," comments Darren from UNSW. "This is clear and independent validation of DNA work on both these extinct humans [the Neanderthals and the Denisovans], confirming today's other big announcement about their deep connections to Australians and other indigenous people in our region."
Although initial studies suggested that Denisovan ancestry was found only in modern human populations from island Southeast Asia and Oceania, more recent studies have suggested that Denisovan ancestry may be more widespread. However, the geographic extent of Denisovan ancestry has not been determined, and moreover the relationship between the Denisovan ancestry in Oceania and that elsewhere has not been studied. Here we analyze genome-wide SNP data from 2493 individuals from 221 worldwide populations, and show that there is a widespread signal of a very low level of Denisovan ancestry across Eastern Eurasian and Native American (EE/NA) populations. We also verify a higher level of Denisovan ancestry in Oceania than that in EE/NA; the Denisovan ancestry in Oceania is correlated with the amount of New Guinea ancestry, but not the amount of Australian ancestry, indicating that recent gene flow from New Guinea likely accounts for signals of Denisovan ancestry across Oceania. However, Denisovan ancestry in EE/NA populations is equally correlated with their New Guinea or their Australian ancestry, suggesting a common source for the Denisovan ancestry in EE/NA and Oceanian populations. Our results suggest that Denisovan ancestry in EE/NA is derived either from common ancestry with, or gene flow from, the common ancestor of New Guineans and Australians, indicating a more complex history involving East Eurasians and Oceanians than previously suspected.
However, the new evidence shows that these people did not arrive in an empty wilderness. Stone tools and charcoal from the site in Brazil show evidence of human habitation as long ago as 50,000 years.
he Neanderthal had a feature which was unique to them (they ALL had it) and is found in some modern humans: the retromolar gap or retromolar space.
A paper published in March 2015, "The Retromolar Space: A Morphological Curiosity Observed Amongst the Protohistoric Arikara and Mandan" by C. de la Cova DOI: 10.1002/oa.2451 International Journal of Osteoarchaeology, noted that it is quite frequent among two American Native groups, the Arikara and the Mandan peoples:
Abstract
The retromolar space (RMS), defined in paleoanthropology as a space posterior to the third molar, between the distal edge of the tooth and the anterior margin of the ascending ramus when the mandible is held in lateral view, has been described as an autapomorphic trait unique to Neandertals despite its presence in anatomically modern humans (AMHs). This study examined RMS prevalence in a sample of Protohistoric Arikara and Mandan Amerindians to determine what craniofacial morphology is correlated with the RMS. It was hypothesized that the feature would be present in the Amerindians studied and associated with a long cranial length, a large nasal height, midfacial prognathism, a broad mandible, and dental wear. The results indicated that RMSs were present in the Arikara and Mandan and significantly correlated with cranial length, cranial breadth, nasal height, bizygomatic breadth, basion-nasion length, basion-nasiospinale, mandible length, gonial angle, bigonial breadth, and dental wear. Thus, RMSs are associated with a dolichocephalic skull, wide cranial and facial breadth, a prognathic face, large nose, and a corresponding wide and long mandible with a reduced gonial angle. This suggests that the RMS is the result of these features merging together in the craniofacial complex and should not be considered a Neandertal autapomorph.
Of course, the conclusion that Ms. Cova reaches is that it is not an exclusive Neandertal feature but that it is related to a certain skull morphology that these natives have...
How about testing another hypothesis: the natives have it because they have a high admixture with Neandertals and got the genes that produce the retromolar gap from the Neandertals themselves... maybe even admixing in America and not in Asia before migrating to the New World.
[/ex]
retromolar gap
Patagonian Monsters
And more musings from Austin
Neanderthals, Psoriasis and Native Americans... a Link
A very interesting paper by Yen-Lung Lin, Pavlos Pavlidis, Emre Karakoc, Jerry Ajay, and Omer Gokcumen, " Variants Shared with Archaic Hominin Genomes" takes a look at "polymorphic human deletions that are shared with archaic hominin genomes, approximately 87% of which originated before the Human–Neandertal divergence (ancient) and only approximately 9% of which have been introgressed from Neandertals (introgressed)...", some of these deletions are the cause of well known diseases.
I decided to see if there were any hints at a link between Native Americans and diseases prevalent among Neanderthals and this is what I found:
The previous paper by the same team (The Evolution and Functional Impact of Human Deletion Variants Shared with Archaic Hominin Genomes by Yen-Lung Lin, Pavlos Pavlidis, Emre Karakoc, Jerry Ajay, and Omer Gokcum. Mol. Biol. Evol. doi:10.1093/molbev/msu405 Advance Access publication January 2, 2015) states that one of the deleted sequences shared by humans and Neanderthals is the LCE3C gene deletion: "...which has been strongly associated with psoriasis (de Cid et al. 2009). The allele frequency of LCE3C gene deletion is extremely high among Eurasians, reaching to over 70% allele frequency in some European and Asian populations..." it is the authors' "understanding that this deletion has been maintained in high allele frequencies since before Human– Neandertal divergence."
patagoniamonsters.blogspot.com...
And about Native americans inheriting the diabetes risk gene from Neanderthal
Mexicans and other Latin Americans have a higher risk of diabetes because of a Neanderthal gene mutation, researchers say.
and
Although this gene variant is common among people with recent Native American ancestry and is also found in about 20 percent of East Asians, only 2 percent of Europeans have it, and no known Africans carry SLC16A11. This pattern is somewhat unusual; modern humans arose in Africa, so nearly all common human genetic variants are found in African populations. [Top 10 Mysteries of the First Humans]
To uncover the roots of this odd pattern, the researchers investigated ancient human DNA and found the high-risk mutation of this gene was apparently inherited from Neanderthals, the closest extinct relatives of modern humans. Recent analysis of Neanderthal DNA revealed the ancestors of modern humans interbred with Neanderthals; the first high-quality genome sequence from a Neanderthal suggests about 1.5 percent to 2.1 percent of the DNA of modern humans living outside Africa is Neanderthal in origin. In contrast, Neanderthal DNA is much less common among modern Africans, matching these latest findings.
Diabetes in Native Americans
What's most interesting about that work is that another recent paper, im trying to track it down, shows that meso americans, specifically a group of yucatan maya have the highest levels of neanderthal ancestry of all modern humans.
Neandertal in the (immediate) family tree
Early European may have had Neanderthal great-great-grandparent
One of Europe’s earliest known humans had a close Neanderthal ancestor: perhaps as close as a great-great-grandparent.
The finding, announced on 8 May at the Biology of Genomes meeting in Cold Spring Harbor, New York, questions the idea that humans and Neanderthals interbred only in the Middle East, more than 50,000 years ago.
Qiaomei Fu, a palaeogenomicist at Harvard Medical School in Boston, Massachusetts, told the meeting how she and her colleagues had sequenced DNA from a 40,000-year-old jawbone that represents some of the earliest modern-human remains in Europe. They estimate that 5–11% of the bone's genome is Neanderthal, including large chunks of several chromosomes. (The genetic analysis also shows that the individual was a man). By analysing how lengths of DNA inherited from any one ancestor shorten with each generation, the team estimated that the man had a Neanderthal ancestor in the previous 4–6 generations. (The researchers declined to comment on the work because it has not yet been published in a journal).