4,500-year-old tomb in France reveals secrets of how 'European genome' came to be

High-resolution analysis of the genomes of individuals buried in a 4,500-year-old collective tomb at Bréviandes-les-Pointes, near the French town of Troyes, has revealed a surprising story with far-reaching implications. As detailed in an article in the journal Science Advances, the final stage in the formation of the European genome is still present in many present-day Europeans.

The human genome is the totality of the genetic information carried by our DNA, and it partially reflects the History of our ancestors. The genome of present-day Europeans was formed over a period of more than 40,000 years as a result of various migrations and the resulting mixing of populations. It is thus made up of the complex heredity of the small populations of hunter-gatherers who occupied Europe until the arrival, around 8,000 years ago, of populations from Anatolia and the Aegean region, who descended from those who invented agriculture and animal domestication in the Fertile Crescent. These Neolithic farmers interbred with the local hunter-gatherers and contributed a very important part of the genome of many of today's Europeans.

Finally, at the end of the Neolithic 5,000 to 4,000 years ago, nomadic populations from the Pontic steppes (north of the Black Sea stretching from the Danube to the Urals) migrated to Europe and contributed the third of the main genomic components that have endured in Europeans over the following millennia to the present day.

Although today the deciphering — known also as sequencing — of this genetic information is a routine process, this approach remains tricky for the genomes of individuals who lived in the past. All we have left of them are a few more or less fragmented skeletons. Some parts of these skeletons may still contain traces of preserved DNA, but it is fragmented and sparse, which makes it a methodological challenge to analyze.

Our team at the Institut Jacques Monod has taken up this challenge and optimized the methods so that we could obtain reliable results. This enabled us to analyze ancient genomes using the most advanced bioinformatics and statistical methods.

A witness to cross-breeding between populations

Our analyses of the genomes of seven individuals from the Bréviandes tomb, combined with analyses of the morphology of the bones carried out by anthropologists from Inrap, have shown that the tomb held:

• A woman who was older than 60 when she died.
• her son, an adult man aged around 20-39
• her grandson, aged around 4-8
• the grandson’s mother, aged 20-39
• a young woman aged 20-39
• the young woman’s newborn
• a child aged between 6-10

The last three individuals were not related to the others in the grave, and the last child was not related to any of the others. The fathers of the adult man, the newborn baby and the lone child were not present. It was can therefore be surmised that this not the grave of a single biological family. On the other hand, all the female individuals carried a hereditary component characteristic of the populations of southern France and southwestern Europe, and this common origin outside the area of the tomb might explain why they were buried together with their offspring.