Oldest Human DNA Reveals Mysterious Branch of Humanity

[Buster's Uncle]

Oldest Human DNA Reveals Mysterious Branch of Humanity
LiveScience.com
By Charles Q. Choi, LiveScience Contributor  3 hours ago



The oldest known human DNA found yet reveals human evolution was even more confusing than before thought, researchers say



The oldest known human DNA found yet reveals human evolution was even more confusing than thought, researchers say.

The DNA, which dates back some 400,000 years, may belong to an unknown human ancestor, say scientists. These new findings could shed light on a mysterious extinct branch of humanity known as Denisovans, who were close relatives of Neanderthals, scientists added.

Although modern humans are the only surviving human lineage, others once strode the Earth. These included Neanderthals, the closest extinct relatives of modern humans, and the relatively newfound Denisovans, who are thought to have lived in a vast expanse from Siberia to Southeast Asia. Research shows that the Denisovans shared a common origin with Neanderthals but were genetically distinct, with both apparently descending from a common ancestral group that had diverged earlier from the forerunners of modern humans.

Genetic analysis suggests the ancestors of modern humans interbred with both these extinct lineages. Neanderthal DNA makes up 1 to 4 percent of modern Eurasian genomes, and Denisovan DNA makes up 4 to 6 percent of modern New Guinean and Bougainville Islander genomes in the Melanesian islands.


Pit of Bones

To discover more about human origins, researchers investigated a human thighbone unearthed in the Sima de los Huesos, or "Pit of Bones," an underground cave in the Atapuerca Mountains in northern Spain. The bone is apparently 400,000 years old.

"This is the oldest human genetic material that has been sequenced so far," said study lead author Matthias Meyer, a molecular biologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. "This is really a breakthrough — we'd never have thought it possible two years ago that we could study the genetics of human fossils of this age." Until now, the previous oldest human DNA known came from a 100,000-year-old Neanderthal from a cave in Belgium.

The Sima de los Huesos is about 100 feet (30 meters) below the surface at the bottom of a 42-foot (13-meter) vertical shaft. Archaeologists suggest the bones may have been washed down it by rain or floods, or that the bones were even intentionally buried there.



The thighbone of the 400,000-year-old hominid from Sima de los Huesos, Spain.


This Pit of Bones has yielded fossils of at least 28 individuals, the world's largest collection of human fossils dating from the Middle Pleistocene, about 125,000 to 780,000 years ago.

"This is a very interesting time range," Meyer told LiveScience. "We think the ancestors of modern humans and Neanderthals diverged maybe some 500,000 years ago." The oldest fossils of modern humans found yet date back to about 200,000 years ago.


Denisovan relative?

The researchers reconstructed a nearly complete genome of this fossil's mitochondria — the powerhouses of the cell, which possess their own DNA and get passed down from the mother. The fossils unearthed at the site resembled Neanderthals, so researchers expected this mitochondrial DNA to be Neanderthal.

Surprisingly, the mitochondrial DNA reveals this fossil shared a common ancestor not with Neanderthals, but with Denisovans, splitting from them about 700,000 years ago. This is odd, since research currently suggests the Denisovans lived in eastern Asia, not in western Europe, where this fossil was uncovered. The only known Denisovan fossils so far are a finger bone and a molar found in Siberia. [Denisovan Gallery: Tracing the Genetics of Human Ancestors]

"This opens up completely new possibilities in our understanding of the evolution of modern humans, Neanderthals and Denisovans," Meyer said.

The researchers suggest a number of possible explanations for these findings. First, this specimen may have been closely related to the ancestors of Denisovans. However, this seems unlikely, since the presence of Denisovans in western Europe would suggest an extensive overlap of territory with Neanderthal ancestors, raising the question of how both groups could diverge genetically while overlapping in range. Moreover, the one known Denisovan tooth is significantly different from teeth seen at the Pit of Bones.

Second, the Sima de los Huesos humans may be related to the ancestors of both Neanderthals and Denisovans. The researchers consider this plausible given the fossil's age, but they would then have to explain how two very different mitochondrial DNA lineages stemmed from one group, one leading to Denisovans, the other to Neanderthals.

Third, the humans found at the Sima de los Huesos may be a lineage distinct from both Neanderthals and Denisovans that later perhaps contributed mitochondrial DNA to Denisovans. However, this suggests this group was somehow both distinct from Neanderthals but also independently evolved several Neanderthal-like skeletal features.

Fourth, the investigators suggest a currently unknown human lineage brought Denisovan-like mitochondrial DNA into the Pit of Bones region, and possibly also to the Denisovans in Asia.

"The story of human evolution is not as simple as we would have liked to think," Meyer said. "This result is a big question mark. In some sense, we know less about the origins of Neanderthals and Denisovans than we knew before."

The scientists now hope to learn more about these fossils by retrieving DNA from their cell nuclei, not their mitochondria. However, this will be a huge challenge — the researchers needed almost 2 grams of bone to analyze mitochondrial DNA, which outnumbers nuclear DNA by several hundred times within the cell.

The scientists detailed their findings in the Dec. 5 issue of the journal Nature.


http://news.yahoo.com/oldest-human-dna-reveals-mysterious-branch-humanity-181139436.html

[Buster's Uncle]

'Pit of Bones' Yields Oldest Known Human DNA
ABC News
By GILLIAN MOHNEY | ABC News – 3 hours ago






Researchers have uncovered a new clue about human origins after discovering the oldest known human DNA in a legendary Spanish archeological site called Sima de los Huesos, or the "Pit of Bones."

Researchers were able to extract DNA from a leg bone that was estimated to be 400,000 years old. After extracting the DNA from a femur bone, Matthias Meyer, who published his findings in a study in the journal Nature, was able to replicate the entire genome for the ancient human relative.


News on the Human Genome Project 

The genetic sequence surprised researchers, who thought it was likely that the sequence would reveal that remains were related to the Neanderthals. Instead, the genetic sequence revealed that this early human species is related to another genetic cousin of modern humans,the mysterious Denisovans.

Little is known about the Denisovans, who are thought to have been common throughout the regions now known as Asia and Eastern Europe. This early human species was discovered after genetic sequencing was used to map DNA through the ancient pinkie bone of a girl in 2010.

Anthropologists and genetic experts said the findings from the Pit of Bones could help shed light on how early human species evolved and spread across different continents.

"This places what we have to assume from the genetic sequence is an earlier branch of our family that goes back even further" in time, said Kenneth Kidd, professor of genetics at the Yale University School of Medicine. Kidd said since the DNA was from 400,000 years ago, this mysterious human relative likely predated most Neanderthals.

Kidd explained that one reason there is little known about the Denisovans is that "the Neanderthals may have annihilated the Denisovans," similar to how the Neanderthals died off as modern humans became more populous.

If you're wondering if you're related to the ancient DNA, Kidd said there is no evidence that the Denisovans provided any genetic material for the modern human race.

Theodore Schurr, professor of anthropology at the University of Pennsylvania, said the findings were significant since it showed clearly how DNA mapping was changing the field of anthropology. Schurr said solely from the skeletal remains researchers thought the human species appeared to be related to Neanderthals.

"This is also significant because it's the DNA coming from the oldest remains," said Schurr. "It's interesting to compare the skeletons to the genetics because the stories may not match up."


http://gma.yahoo.com/39-pit-bones-39-yields-oldest-known-human-203310093.html

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Early Human Interbreeding More Widespread Than Thought, Study Suggests
By Robert Lee Hotz  Updated Dec. 4, 2013 7:30 p.m. ET



Researchers analyzing DNA found in ancient bones from Spain discovered a stranger in the mix, suggesting that interbreeding between human species in Ice Age Europe was more widespread than suspected, according to research published Wednesday.

Geneticists led by Matthias Meyer at the Max Planck Institute for Evolutionary Anthropology in Germany extracted the oldest known human DNA—dating back more than 300,000 years—from a fossil thigh bone preserved at the bottom of a cave shaft called Sima de los Huesos—the pit of the bones—in northern Spain, where remains of 28 early humans belonging to an unknown species have been discovered.

By the appearance of their bones, these primitive precursors to modern humankind likely looked most like stocky, barrel-chested Neanderthals. But the genetic analysis reported in Nature showed that their maternal DNA, drawn from special cell structures called mitochondria, was different than that of Neanderthals and also unlike that of more modern humans. It was most closely related to a mysterious species called the Denisovans.



The remains of an early human discovered in a cave in northern Spain Javier Trueba/Madrid Scientific Films


The Denisovans themselves were unknown to science until 2010, when their DNA was first identified from the fingertip of a young female discovered in a cave in Siberia. Her remains dated to about 40,000 years ago, offering evidence that Neanderthals, anatomically modern humans and Denisovans coexisted at that time.

Wednesday's telltale snippet of maternal DNA from a much earlier era left independent experts in human origins perplexed about the ancestral relationships recorded in the chemistry of human heredity.

"No one knows what to make of this," said anthropologist Ian Tattersall at the American Museum of Natural History in New York, who wasn't involved in the research. "We are lifting the edge of the curtain onto something more complex than any of us had ever thought."

Experts offered four tentative theories to account for the puzzling pedigree revealed in the mitochondrial DNA, which is passed from a mother unchanged to all her children: The people at the Sima cave could have been a distinct species that had interbred with Denisovans. They also could have been related to the ancestors of Denisovans; the ancestors of both Denisovans and Neanderthals; or related to an older human species that lived elsewhere in Europe and Asia, such as Homo heidelbergensis. Or all of the above.

"I would speculate the likelihood of interbreeding is quite high," Dr. Meyer said.

Indeed, there is a little bit of Neanderthal DNA in every modern non-African today, according to a 2010 genetic analysis of ancient and modern genomes. Last year, researchers at the Max Planck Institute reported that there is a bit of Denisovan in some people as well—as much as 6% of the genomes of some modern South Pacific Islanders.





"This tells us something interesting about how our species evolved," said population geneticist Michael Hammer at the University of Arizona. "It may be that interbreeding was a common process in all of human evolution."

Under most circumstances, genetic material quickly breaks down and degrades, but the cool, humid and undisturbed air of the Sima cave shaft offered almost perfect conditions for the preservation of the fragile molecules.

"It is the most perfect fridge you could build to preserve ancient fossil DNA," Dr. Meyer said.

The researchers used a dental drill to extract about 2 grams of relatively pristine bone. Despite precautions, the Sima material was contaminated by modern human DNA. But the scientists separated the ancient and contemporary sequences by sorting DNA fragments based on the distinctive molecular signature of genetic decay. Dr. Meyer and his colleagues then stitched together very small fragments of intact DNA to reconstruct and sequence the genome of the Sima individual's mitochondria—energy-producing structures that every cell has by the hundreds.

The researchers compared the Sima genetic sequence to the mitochondrial DNA from modern and ancient humans, Neanderthals, Denisovans, chimpanzees and bonobos. The Sima sample overlapped only with Denisovans, according to the researchers.

"We thought they were Neanderthal relatives but the mitochondrial genome told a different story," said Juan-Luis Arsuaga, director of the Center for Contemporary Human Evolution at the Institute of Health Carlos III in Madrid, who has worked at the Sima site since 1983. "It was unexpected and shocking."


http://online.wsj.com/news/articles/SB10001424052702303722104579238193023240718