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Genetic sequence from 24,000-year-old boy is oldest genome from human to date

By Catholic Online (NEWS CONSORTIUM)
November 21st, 2013
Catholic Online (www.catholic.org)

What are the origins of Native Americans? Thanks to the genome of a young boy who died 24,000 years ago in south-central Siberia, scientists are closer to answering that question. The said genetic sequencing is the oldest genome performed on a human to date.

LOS ANGELES, CA (Catholic Online) -  DNA extracted from the bones of the prehistoric boy, who died while only a toddler, proved that he shared genetic traits with Western Europeans and native Americans - but none with East Asians. The discovery has surprised and perplexed the lead scientist conducting the research.

"At first I thought it was contamination, to be honest. It was just so unexpected," Eske Willerslev, director of the Center for GeoGenetics at the University of Copenhagen says.

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Native Americans are genetically associated with East Asians. Many believe that the first Americans were descendents of Asian groups who arrived via Siberia and the Beringia land bridge. There has been no specific, contemporary East Asian population that modern native Americans can be linked to.

The discovery in Washington's Beringia land bridge of Kennewick Man in 1996, which was a complete 9,500-year-old skeleton with non-Asian features ignited years of controversy. North American archeological finds further compounded that uncertainty.

The X haplogroup, a trait that some native Americans and Europeans share is believed to be the result of post-colonial contact or prior ancestry. One theory, the Solutrean hypothesis, even held that the first people in America were Europeans who came by boat.

Willerslev along with American colleague Kelly Graf wondered if a very old and very rare skeleton housed at a museum in St. Petersburg, Russia might hold clues to these questions.

The bones in question belonged to a boy who died as a toddler some 24,000 years ago. Discovered at the Mal'ta archeological site, which sits near Lake Baikal in Siberia and which was excavated between 1928 and 1958. It was believed that the human remains may contain answers.

Willerslev's team received permission to sample 150 milligrams of the Mal'ta boy's arm bone and sequence his DNA in 2009. They believe it is the oldest genome from an anatomically modern human ever reported.

Mitochondrial DNA showed that the boy belonged to haplogroup U, which was found with high frequency among Stone Age European hunter-gatherers.

Willerslev at first thought it must be a mistake. Further testing showed more genetic signatures shared with Western Europeans and with native Americans.

Willerslev and his co-authors now estimate that modern native Americans share between 14 and 38 per cent of their DNA with this boy and the population he belonged to. The other two-thirds can be traced back to East Asian groups.

Inconclusively, this suggests that the people who first populated this continent were the result of intermixing between two groups, if not more.

"It shows that native Americans, as a group, are not just a branch of East Asians, but were formed in their own right by the meeting of different peoples," Willerslev says.

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