Genetic Genealogy & Ancient DNA (TITLES/ABSTRACTS)

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Revealing close and distant relatives in ancient DNA with unprecedented precision (phys.org)

If two persons are biologically related, they share long stretches of DNA that they co-inherited from their recent common ancestor. These almost identically shared stretches of genomes are called IBD ("Identity by Descent") segments. Up to the sixth-degree relatives—such as second to third cousins would be, or a great great great great grandparent—the two relatives even share multiple IBD segments. Personal genomics companies such as 23andme or Ancestry detect those segments routinely in DNA of their customers, and use this signal to distinctively reveal biological relatives in their databases.

In a new study published in Nature Genetics, researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and Harvard University, U.S., has now developed a powerful new tool named "ancIBD" to extract these IBD segments also in genomes of humans who lived hundreds, thousands, or even tens of thousands of years in the past.

The critical challenge was that such ancient genomes are often very degraded and therefore of much worse quality than modern DNA, so the authors had to come up with an innovative trick to fill in gaps in ancient genomes using modern reference DNA panels.