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New Genome Technique Sheds Light on Denisovans

Aug 31, 2012 09:06 AM EDT
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Scientists have sequenced the genome of lesser known Denisovan race that might possibly shed some light on the evolution of present-day humans.

An international team of researchers led by Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, sequenced the genome of a small section of a finger bone and two teeths that were discovered during an excavation at the southern Siberia's Denisova Cave in 2008.

Using a new sequencing technique, the experts sequenced every position in the genome by splitting the double strands of DNA. They compared the complete genome sequence of the Denisovan race with that of the Neanderthals and 11 genomes of modern-day humans. 

"This is an extinct genome sequence of unprecedented accuracy", Matthias Meyer, the lead author of the study, said in a statement. "For most of the genome we can even determine the differences between the two sets of chromosomes that the Denisovan girl inherited from her mother and father," he said. 

Based on the genome sequence, the experts compared the two different types of chromosomes of the girl inherited from her mother and father. They suggested a low genetic diversity in the Denisovan population compared to the present-day humans that could possibly mean that the Denisovan population didn't expand much and faced extinction as modern humans started spreading.  

The experts aligned the Denisovan genome with that of the human genome and by counting the genetic mutations they estimated that the Denisovans split from the modern humans between 170,000 and 700,000 years ago. Their study also suggested that the Denisovans had dark skin with brown hair and brown eyes. They determined that the girl could have died 80,000 years ago.

The findings also hint at the possibility that the Denisovans and the Neanderthals descended from one group of population that migrated from Africa.

While earlier studies have suggested that the Denisovans existed along with the Neanderthals, they were also found to have interbred with ancestors of ancient Southeast Asians after some Denisovan DNA were found in some present-day island Southeast Asians.

Surprisingly, the team also found that the Southeast Asians have more Neanderthal DNA than the Europeans have, which is peculiar because the most number of Neanderthal fossils were found in Europe.

Experts also confirmed their previous studies based on the new genome sequence, which suggested that the three percent of the genomes of Papua New Guinea people living currently come from Denisovans, while places like Han and Dai in China have just a trace of Denisovan DNA.

The findings of the study, "A High-Coverage Genome Sequence from an Archaic Denisovan Individual," are published in the journal Science

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