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.
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