Deep insights into old family relationships

The new method has uncovered, among other things, two relatives whose remains were once buried 1,500 kilometers apart in Eurasia. © Ringbauer & Huang et al., Nature Genetics (2023) / 123RF | hedge

Who was once related to whom? A new method for analyzing ancient DNA can now show the connections between people much more extensively than before: from the previously possible third degree of relationship, the range expands to the sixth. Using interesting examples, the scientists have already been able to document how the process can be used to uncover previously unknown connections within and between groups of people.

In addition to shovels, brushes, etc., modern genetics has increasingly become an important tool in researching human history in recent years: remains of genetic material can provide interesting information from the past. By comparing ancient DNA that can be obtained from human bones, ancestry relationships can also be identified. Because related people have the same parts of their genome that they inherited from their last common ancestor. However, compared to “fresh” genetic material, the possibilities for detecting these so-called IBD segments (Identity by Descent) have so far been limited. Because genomes that are centuries or millennia old are often only preserved in fragments.

Cleverly filled gaps

But now, using sophisticated genomic data processing techniques, an international team of researchers has succeeded in filling gaps in ancient genomes with modern reference DNA. This then makes previously hidden IBD segments clear, as the team was able to demonstrate using reference examples. Called “ancIBD,” the scientists are now presenting the process as a new instrument for analyzing ancient DNA data.

“By identifying regions in the genome that individuals have in common with one another, we can now detect pairs of relatives up to the sixth degree in ancient genomes, whereas previous methods could only detect relatives up to the third degree,” summarizes first author Yilei Huang from the Max Planck Institute for Evolutionary Anthropology in Leipzig. This means that in historical or prehistoric people, links can be shown between second or third cousins ​​or to a great-great-great-great-grandparent.

In their study, the researchers are already presenting application results of their new method. They used ancIBD to analyze a data set of 4,248 previously published genomes, which come from human remains up to 50,000 years old from various parts of Eurasia. As they report, ancIBD actually identified many previously undetected relative pairs in the genomic data. Connections within certain groups and also long-distance relationships emerged.

Interesting kin pairs identified

In one particularly striking case, scientists identified two people linked by fifth-degree kinship who lived in Eurasia about 5,000 years ago. The interesting thing was that their respective graves were around 1,500 kilometers apart in Mongolia and Russia. The result reflects the enormous mobility of these people or their close ancestors.

As the team further reports, in addition to familial relationships, the analysis tool can also provide evidence of connections at the population level: using an average rate of similar DNA segments, it can show mixing between groups of people, the researchers explain. “We have discovered exciting new connections between ancient cultures – sometimes over long distances and over a period of just a few hundred years,” says senior author Harald Ringbauer from the Max Planck Institute for Evolutionary Anthropology. Among other things, the researchers discovered the signature of a gene flow in Eurasia that began around 5,000 years ago. Europeans associated with the Corded Pottery culture therefore had a biological connection with the Yamnaya shepherds of the Pontic-Caspian steppe.

The scientists summarize that the new method for screening ancient DNA could provide insights into human history on various levels: on the micro level, with a focus on individual life paths, and on the macro level, when it comes to researching significant cultural-historical developments. The researchers emphasize that the potential is constantly increasing. The amount of archaeogenetic data increases enormously every year.

Source: Max Planck Society, specialist article: Nature Genetics, doi: 10.1038/s41588-023-01582-w

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