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Tracing Human Migration
Megan Sever

Testing your DNA

Many people are fascinated with learning about their family tree — for example, tracing long-lost relatives through Ellis Island to learn when they left their home countries and set foot in America. Now, imagine finding out not just about the past few generations, but also about your ancestors’ moves from when they first left Africa as much as 60,000 years ago. A new partnership between National Geographic Society, IBM and the Waitt Family Foundation, aims to do just that: trace the ancient migratory paths our ancestors took to populate the planet.

The Genographic Project researchers will collect and analyze the DNA of 100,000 indigenous people in 1,000 targeted populations throughout the world, as well as the DNA of other interested members of the public. The result will be an anthropological database that can be “the ultimate guide to human history,” says Spencer Wells, a population geneticist and Explorer-in-Residence at National Geographic who dreamt up and is leading the project, which launched this spring. “The goal is to trace the migratory history of the human species, to map how the Earth was populated,” he says.

Although humans in present form originated in Africa about 200,000 years ago, clues from genetics, archaeology and paleoanthropology show that it was not until around 60,000 years ago that people first began wandering off the continent to populate the planet. “Our DNA carries a story that is shared by everyone,” Wells says, and everyone’s DNA can be traced to a common ancestor in Africa — an “Adam,” who lived around that 60,000-year mark, or an “Eve,” who lived around 150,000 years ago, the earliest traceable male and female.

People receive about half of their genes from their mother and half from their father, representing a mixture of DNA passed down from their ancestors. Geneticists rely on this chromosomal inheritance to track genetic histories. Occasional mutations in this genetic sequence stick out — they become unique markers of descent that get passed down from generation to generation. This isn’t the genetic material that determines if you get blue eyes from your mother or brown eyes from your father; this is the part that remains unchanged from your original ancestor to you.

Because these genetic markers originate in a single individual, they can be traced back to the particular geographic region where that person and his or her descendents lived, Wells says. As indigenous populations have remained in close to the same location for hundreds of generations, their DNA likely contains key genetic markers that have remained relatively unaltered, he says. Thus, their DNA can provide a starting place for the rest of us to figure out when our ancestors left these populations and migrated outward. It is especially important to do this now, he says, as indigenous populations are shrinking rapidly as people are migrating and mixing to a much greater extent than in the past.

The Genographic Project has set up 10 centers around the world to work with indigenous populations to collect and analyze their DNA. The principal investigators will collect blood samples from members of indigenous populations who are willing to participate, take the samples back to the lab, and then isolate and analyze the DNA, molecule by molecule, to decode the unique genetic markers. Women’s results come from their maternal line, via mitochondrial DNA. Men will be tested via the Y chromosome, which provides slightly more easily traceable results, Wells says. Other people can volunteer to submit DNA to track their lineages by purchasing a kit from the National Geographic Web site for $99.95, with the proceeds going to participating indigenous populations (see sidebar, below).

Whether for an indigenous person or an interested member of the public, the results are the same: a familial history that goes back thousands of years. For example, Julius Indaaya Hun/!un//!ume, an indigenous man who is chieftain for the Hadzabe tribe, a nomadic hunter-gatherer people who live in northern Tanzania, can trace his lineage straight back 60,000 years to the same location to “Haplogroup A.” A haplogroup is a branch of a family tree defined by unique genetic markers that link the members of that group back to the marker’s first appearance in the group’s most recent common ancestor. The tribal chief’s people have not moved; he is “a relic.”

By contrast, the Genographic Project’s Communications Director Lucie McNeil, a British woman of Anglo descent who provided her DNA sample, tested as part of “Haplogroup J,” a group that began 150,000 years ago with the first traceable woman in Africa and has since migrated extensively and undergone a number of genetic mutations. Haplogroup J is actually one of the more common groups for people of European descent, Wells says.

Fifty thousand years ago, when the climate changed and the Sahara became inhabitable, McNeil’s African ancestors migrated northward to the Middle East, where they likely lived alongside Neanderthals. Over the next 40,000 years, her ancestors wandered toward the Near East, near the present-day Black Sea. About 10,000 years ago, her lineage in the Near East became some of the world’s first farmers; their agricultural success spawned population bursts and encouraged migration into Europe. Today, her lineage is found throughout Europe and the Middle East.

Although that information is pretty specific, there are many genetic details that have not been worked out yet, Wells says, such as what happened after McNeil’s ancestors moved into Europe, and more details about specific movements within each of the larger timescales, including the 100,000 years her ancestors seem to have just been hanging out in Africa. As more people participate, Wells says, the scientists will learn more about the different lineages, information that they will upload to the Web site so participants can learn more as well.

Throughout the project, Wells and colleagues will be working with anthropologists, archaeologists, geologists and geneticists to create as detailed a human history as possible. Using ancient DNA from bodies in museums or collected during archaeological digs, and DNA collected from the participants in the project, Wells says he hopes they will be able to learn more about the current patterns of diversity and how we evolved so-called phenotypic changes — such as skin color or facial shapes and features — so quickly (at least on a geologic timescale).

The researchers also hope to learn about when we humans spread throughout the planet, such as when the first wave of migration hit Australia or Asia, says Alan Cooper, a geneticist and geologist at the University of Adelaide in Australia, who is the principal investigator charged with ancient DNA studies for the project. He says that the scientists may even be able to solve the decades-old debate about when humans first set foot on North America (see story, this issue).

“I think the study will certainly produce a far more accurately resolved picture of the paths and complexities of human migration and evolution,” Cooper says. Judging the timing of the events, however, is “far more problematic,” as molecular clocks are not as reliable for time periods of less than 1 million years, “which of course includes most of the interesting events within human evolution.” Still, he says, “the data will be our best stab” at dating human movement and evolution.

The Genographic Project was launched in April and will continue for the next five years, with the end result being a comprehensive database filled with the world’s DNA, Wells says. Considering the project is still just getting under way, Cooper says, there’s no telling how things will develop and what scientists will learn about our origins.

Testing your DNA

As scientists traipse across the world collecting DNA from indigenous people in hopes of learning how humans migrated out of Africa to populate the planet, interested members of the general public can also participate. They can contribute their DNA to the study and learn about their own genetic journeys.

People can purchase a testing kit from the National Geographic Web site for $99.95, which they will receive in the mail. The kit includes a DVD explaining the project, a map tracing ancient migratory paths, a consent form (allowing the project to test the DNA) and two cheek swabs. The testing procedure is simple: Scrape the inside of the cheek for 60 seconds (as is seen on detective shows on TV when they collect DNA samples), stick the swab into a vial containing a unique identification number and send the vial to a DNA testing facility. Besides the DNA, the only personal information participants provide about themselves is their gender, so the testing facility knows to check mitochondrial DNA for women or the Y chromosomal DNA for men. The DNA results are completely anonymous and will be thrown out after they have been entered into the migratory database.

Roughly two weeks after sending in the kit, participants can log on to the project’s Web site using their unique kit identification number to track their DNA’s progress. (My kit got lost, so I don’t have my results to share, but National Geographic was quick to send me a new kit for free — I get the feeling I’m not the first person to whom this happened.) Assuming all goes well, throughout the following four weeks, participants can watch as scientists analyze their DNA. About six weeks after the kit is received, participants can upload the final results.

The first thing participants will see is their DNA sequence and an explanation of what their unique genetic markers show. Participants are then taken “on a journey of their DNA,” says Spencer Wells, director of the Genographic Project. They can follow their genes back to the first member of the family tree in Africa as many as 150,000 years ago.

Over the five-year course of the project, participants are encouraged to log into the Web site periodically to check for updates on their genealogy. Some genetic lines are already fairly well-mapped, while less is known about others. But as more people participate, the project scientists will update the genetic lines.

Proceeds from the sale of the kits will go back to the participating indigenous populations, as part of the Genographic Legacy Project.

MS

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Sever is a staff writer for Geotimes.

Links:
National Geographic
"Footprints push back American migration," Geotimes, September 2005

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