DNA from 4,000-year-old human sequenced
The DNA of a human who lived 4,000 years ago in Greenland reveals that even ancient men had to worry about baldness.
An international team of scientists sequenced the genome of the man from DNA found in a tuft of hair preserved in the permafrost.
Their study was published this week in the journal Nature.
The researchers said the man — whom they've named Inuk, which means human in Greenlandic — was a member of the Saqqaq culture from northwestern Greenland.
"Inuk" is also the singular of "Inuit," but the scientists said that their Inuk is more closely related to modern-day people from tribes in northwestern Siberia than to the Inuit. They chose the name to acknowledge that the discovery was made in Greenland.
From the genome, the researchers were able to determine that Inuk had brown eyes, darker skin than most Europeans, the blood type A-positive, and shovel-shaped front teeth. They also found that he had a tendency toward baldness and was adapted to cold temperatures.
The genome also suggested that he had thick, dark hair, the only physical trait of Inuk the researchers were able to confirm directly.
Deep freeze preserves genetic material
The tuft of hair was found on the west coast of Greenland, north of the Arctic Circle in 1986. Prof. Eske Willerslev, of the University of Copenhagen, who led the research, only recently found out about the hair, which was stored in the National Museum of Denmark.
"After the Greenland National Museum and Archives granted permission, we analyzed the hair for DNA using various techniques and found it to be from a human male. For several months, we were uncertain as to whether our efforts would be fruitful. However, through the hard work of a large international team, we finally managed to sequence the first complete genome of an extinct human," Willerslev said in a statement.
The deep freeze of the permafrost preserved the genetic material, and the researchers said it's not clear if human remains from warmer places would be suitable for reconstructing genomes.
The scientists said Inuk's ancestors came to the New World from northeastern Siberia between 4,400 and 6,400 years ago, and that their previously unknown migration was separate from the one that brought the Inuit and other North American aboriginal people to the continent.
Very little is known about the Saqqaq people because there are few remains of the culture.
Success hinged on sequencing techniques
Willerslev and his team, which included scientists from Denmark, the U.S., Latvia, the U.K. and China, credited their success in finding Inuk's genome to advances in DNA sequencing techniques.
The team has previously sequenced DNA from cell components, called mitochondria, from an ancient human and a woolly mammoth, but this is the first time that DNA from the nucleus has been completely sequenced.
"Previous efforts to reconstruct the mammoth nuclear genome resulted in a sequence filled with gaps and errors due to DNA damage because the technology was in its infancy. The genome of Inuk is comparable in quality to that of a modern human," said Willerslev.
Willerslev said that other hair samples from around the world, from mummies in museum collections or otherwise preserved, could be usable for similar studies.
"I won't say it will become routine," he told reporters, but "I think it will be something we will see much more in the coming five years."
Scientists have recently reconstructed draft versions of genomes of other species from much older DNA. A study on the woolly mammoth used DNA that was 18,000 years old and 58,000 years old.
With files from The Associated Press