Message from Graham and Peter: Thanks everyone for all of your great questions. We'll answer some of the pending questions, as of 1pm PT May 16th, but won't be answering new ones. Thanks!

We are the authors, Peter Ralph (/u/petrelharp) and Graham Coop (/u/grahamcoop), of a recent paper on The Geography of Recent Genetic Ancestry across Europe.

The article made some news in a number of places with the headline that "Europeans are all related". What does that mean? Didn't we already know that? And how can you show that the Spanish and the Polish have the same ancestors only 1,000 years ago, but also see different effects of events from 1,500 years ago in their genomes? We're ready to talk about genetics, genealogy, and even a little bit of European history (Although note that we're not historians).

Here's a quick intro; there's more detail here.

Few of us know our family histories more than a few generations back. It is therefore easy to overlook the fact that we are all distant cousins, related to one another via a vast network of relationships.

In the paper we use genome-wide data from European individuals to investigate these relationships over the past 3,000 years, by looking for long stretches of genome that are shared between pairs of individuals through their inheritance from common genetic ancestors. We find evidence of ubiquitous recent common ancestry, showing for instance that even pairs of individuals from opposite ends of Europe share hundreds of genetic common ancestors over this time period.

Since the vast majority of genealogical ancestors from 1,000 years ago are not genetic ancestors, this implies that all of the Europeans in our sample share nearly all of their genealogical ancestors only 1000 years ago (albeit to differing extents). Despite this degree of commonality, there are also regional differences. Southeastern Europeans, for example, share relatively more common ancestors that date roughly to the era of the Slavic and Hunnic expansions around 1,500 years ago, while most common genetic ancestors that Italians share with other populations lived longer than 2,500 years ago. The study of long stretches of shared genetic material promises to uncover rich information about many aspects of recent population history.

Ask us anything about our paper!