Ancient DNA reveals genetic relationship between today’s Sardinians and Neolithic Europeans

By: Cathy Yarbrough, contributing science writer 

When Stanford University population geneticist Carlos Bustamante and his team analyzed the ancient DNA (aDNA) of the mummy known as Otzi, the Iceman, they discovered that the 5,300-year-old had a genetic affinity with modern-day Sardinians. However, Otzi was not discovered in Sardinia, a large island in the Mediterranean Sea, but on a glacier thousands of miles away near the Austrian-Italian border.

During subsequent investigations of other ancient genomes that had been uncovered in Europe, the researchers found an explanation for Otzi’s genetic affinity with Sardinians: the mummy’s aDNA represented an ancestry component that was widespread in Europe during the Neolithic period, the last stage of the Stone Age when agriculture spread throughout Europe from the Middle East.

Bustamante concluded that today’s Sardinians are more genetically similar to ancient Europeans than to the current European populations, because the Sardinians remained isolated after the spread of agriculturalists into Europe, and therefore did not undergo admixture with hunter-gatherer groups already living in Europe at the time. Bustamante shared his findings at the 2015 Immunogenomics conference, held in late September at the HudsonAlpha Institute for Biotechnology in Huntsville, Ala.

“Whole genome sequencing of ancient humans and other hominids provides insight into human migration, admixture and disease,” he said. Hominids include humans as well as their erect and bipedal evolutionary ancestors. Admixture, which refers to offspring of two individuals from geographically separated areas, introduces new genetic lineages into a population.

While Otzi’s tissue was well preserved, the aDNA of most ancient hominids is either degraded or contaminated, Bustamante said. To enable scientists to use these aDNA samples in research, Bustamante’s lab invented a procedure to enrich inadequate aDNA samples quickly, accurately and at a relatively low cost.

Bustamante is applying the procedure, named whole-genome in-solution capture (WISC), to understand the origins of the millions of Africans forcibly removed from their homes during the Translantic African slave trade of the 15th to 19th centuries. “We are using DNA to understand who they were, where they came from and who today shares DNA with those people taken aboard the ships,” he said.

Bustamante and collaborators in Denmark used WISC to recover sufficient DNA from the skeletons of three slaves, two men and one woman, who were buried more than 300 years ago on the Caribbean island of St. Martin. The researchers identified characteristics that could be used to pinpoint the regions of Africa where the three individuals were likely born. The scientists compared the DNA characteristics of the three slaves to genomic information from on 11 West African populations. The comparison revealed that one of the males was probably a member of a Bantu-speaking group in northern Cameroon. The other two individuals were shown to share DNA similarities with non-Bantu-speaking populations in modern-day Nigeria and Ghana.

Because of WISC, Bustamante said, “It’s possible to obtain genome-wide aDNA from the tropics and obtain a genetic picture of the slave trade.”

WISC also is being applied to forensics to make predictions about an individual’s hair and eye color from traces of DNA found at crime scenes. For example, Bustamante described a recent use of WISC to describe the features of the suspected murderer in a sexual homicide case in Pennsylvania.

HudsonAlpha will host the 4th Immunogenomics conference Sept. 26-28, 2016.