Mapping Ancient Human Migration With Our Spit

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The story of how our ancestors interacted -- as far back as 150,000 years ago -- is being written by DNA samples from the cheeks of over 500,000 people.

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Pools of salt at the Maras mines in Cuzco dating back to pre-Incan civilizations [JanineCosta/Reuters]

A whole industry dedicated to hawking DNA tests that provide insight into genetic ancestry has sprung up in the last decade or so. But with the unveiling of the second phase of National Geographic's Genographic Project, the power of what can be revealed by analyzing your spit has been taken to the next level. By submitting a sample of DNA from swabbing the inside of your cheek and having it scanned for genetic markers, you can shed light on the paths that indigenous groups traveled across the world for the past 150,000 years.

At this week's Atlantic Meets Pacific conference in La Jolla, California, three Atlantic senior editors and correspondents had their DNA analyzed on stage in front of 200 people. The crowd discovered that Jim Fallows has an uncommon number of Neanderthal genes, Alexis Madrigal might turn out to be the nice Jewish boy his mother-in-law always dreamed of, after all, and Steve Clemons is, unfortunately, not at all related to Genghis Khan.

meritbadgeman.jpgSteve Clemons swabs his cheek for a DNA sample

But beyond providing some genetic punch lines, these DNA samples will become part of a database on ancient human migratory patterns that will eventually become part of the public domain. Although some for-profit companies like 23andme have collected many thousands of genetic samples from paying customers, The Genographic Project aims to collect DNA samples from more than 100,000 indigenous people from around the world, more than ten times the number of indigenous people who have ever been tested. To date, the project has collected 75,000 indigenous samples and almost 450,000 samples from members of the public. This anthropological data will help to fill in large gaps in our knowledge about our distant ancestors and build a public database of information about how different peoples may have migrated throughout time.

This genetic information can only answer certain questions about human history, however. Even though Alexis Madrigal now knows that he has maternal Jewish ancestry, for example, does that make Judaism part of his identity? Dr. Spencer Wells, the director of the Genographic Project, cautions against trying to marry genetic information with an understanding of identity. It is "very clear that you cannot define culture on the basis of genetics," he says, arguing instead that genetics are a "mirror" that can shed light on how different groups might have migrated and interacted throughout time rather than defining" the how and why" behind these actions. 

As researchers gain an even better understanding of genetic diversity and human migration over time, their responsibility to use language carefully -- speaking in terms of likelihoods rather than facts and avoiding scientific claims about ethnic identity, for example -- will only become more critical.

So if genetic tests cannot tell you exactly who you are because of the nature of cultural definitions, and you risk finding out that you are more of a Neanderthal than you would like to admit, is it worth shelling out $200 to discover your deep ancestry?

Maybe so. The paths traveled by our ancestors cannot illuminate what it means to be white, Jewish, or Hispanic, but they can lead us toward a better understanding of forgotten cultures and a fuller story of how human history unfolded. The project itself will even have its own effect on human history, with proceeds going toward preserving at-risk indigenous cultures, defending against the erosion of cultural diversity. And who knows; maybe on top of that you'll discover you are related to Genghis Khan.

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Emma Green is an associate editor at The Atlantic.

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