8 Jul 2005 @ 00:51, by Raymond Powers
EXPLORER: SEARCH FOR ADAM
By Bijal Trivedi
National Geographic Channel
June 16, 2005
Analyzing DNA from the cheek cells of a group of Mongolians enabled
geneticist Spenser Wells, an Explorer-In-Residence at the National
Geographic Society, to figure out whether they were indeed descendants of
the notorious warrior who lived 800 years ago and thousands of miles away.
Such exotic historical enigmas are daily fodder for Wells who is in the
midst of the Genographic Project (GP)‹a massive undertaking to sample human
DNA from around the world to illuminate human genetic and migratory history.
³There is a history book in your DNA [that reveals] how people are related
to each other all over the planet and how we have moved around,² says Wells.
The last 10,000 years are of particular interest to Wells who, since
childhood, wanted to be an historian. ³I was fascinated by Egypt and Greece
and Rome and all of these great empires and I¹m very interested in the
impact of these empires on the patterns of genetic variation‹for example,
can we see traces of the Phoenicians in North Africa?² says Wells.
His latest adventures have led him to discover that Thomas Jefferson¹s
ethnic background is not quite as one would expect. He has hunted down
possible descendents of Solomon, the third king of Israel. And, he has
entered a world where science and religion converge‹the search for what he
calls the ³scientific Adam,² the man who gave rise to all men today and the
³trunk² of the human family tree. Wells has used DNA to trace this common
ancestor back to Africa and perhaps to the very plains where he may have
hunted. He has even identified a living tribe with an ancient lineage that
offers a window into the life of ³scientific Adam²‹and, the face of one of
the tribe members served as a model to determine what he may have looked
like.
Unlike medical geneticists who study genetic changes that cause
morphological differences or diseases, population geneticists like Wells
study genetic changes that don¹t have any effect at all. These changes,
called genetic markers, are created by random mutations in the DNA and are
passed down through the generations. Each population accumulates its own
distinctive set of markers.
As these mutations are pretty rare, if two people share one of these markers
that suggests they share an ancestor. By comparing DNA samples from many
different populations, Wells hopes to reveal the shape of the human family
tree, from twigs to trunk.
Wells has traveled the world studying genetic patterns for about the past 15
years. He¹s completed fieldwork in central Asia, India, and the Middle East
collecting samples from about 10,000 people. Analysis of these samples
revealed a broad-brush view of how man originated in Africa and moved around
planet to Australia and Central Asia.
³But,² says Wells, ³10,000 samples isn¹t enough to reveal details about how
we are all related and moved around.² To figure out the details he proposed
a project that required 100,000 samples‹the Genographic Project.
As part of the GP, 10 centers scattered around the globe will each take
blood samples from 100-200 indigenous populations (50 to 100 individuals per
population) over the next five years. Together the project should yield data
on at least 100,000 individuals.
Everyone knows a little about their parents, grandparents, and maybe even
their great grandparents‹but beyond that is a historical realm. ³People
always ask Œit must be really tough to get samples from tribes in remote
regions¹ but that¹s not true. When you explain to people that they are
carrying this history book in there genome, in their blood, and that you can
help them read it they are fascinated‹most people want to participate.²
³I¹ve sampled in Lebanon and Christians and Muslims alike want to know if
they are related to the Phoenicians‹they are intrigued by the chance they
could be a descendent of this great imperial power,² says Wells.
Similarly on the island of Pate, off the coast of Kenya near the Somalia
border, the people have an oral tradition that they are related to Chinese
sailors who washed ashore on 400-foot ships and married local women. Wells
discovered that the residents of Pate don¹t have any Chinese Y chromosomes
but they have Y-chromosomes from everywhere else‹India, Pakistan, the Middle
East, and Europe. However, the presence of 15th century Chinese pottery on
the island suggests that there may be truth to the tales and more genetic
sampling is needed.
³Genographic is not really a genetics project. It is using genetics as a
tool to study history and anthropology. I¹m interested in the impact of the
Inca empire on the genetic patterns in upper Amazonia, in Central Asia I
want to look at the impact of Alexander the Great,² says Wells as he rattles
of a hit list of historical mysteries that he hopes to solve.
The GP has taken on a particular urgency because of massive migrations
currently in progress. People are leaving their ancient homelands, moving to
the cities, and becoming part of the melting pot. As people marry
individuals from other cultures genetic patterns are quickly scrambled. If
Wells can¹t identify the location where a particular genetic pattern arose,
it becomes tricky to identify how different ethnic groups are related to one
another.
³This makes the job of a population geneticist very difficult because though
you carry your genes with you, you lose the context in which that genetic
variation arose,² says Wells.
A symptom of this mixing is the rapid decline in the number of spoken
languages in the world. In the year 1500, linguists estimate 15,000
languages were spoken; today there are 6,000. By the end of the century
about half to 90% of those are going to be extinct, says Wells. ³We are
going through a period of cultural mass extinction. We have a narrowing
window of opportunity to collect genetic samples from indigenous populations
where people have stayed put for a very long period of time.²
Wells hopes that by studying the DNA from these groups he can locate where
particular genetic changes occurred and when, which will reveal how our
ancestors migrated around the planet.
To date, Wells has visited about 50 countries to sample different genetic
lineages. Of all the indigenous tribes he has met, the Hazabe of Tanzania
have had the greatest impact on Wells.
³I have hung out with other Bushmen and they are fascinating. But most of
them don¹t actually live the hunter-gatherer lifestyle. They can still mock
it up for a film crew but none of them actually live in villages. The Hazabe
live as hunter-gatherers. They are actually pulling up trees and carving
bows and arrows and they make fire by rubbing sticks together, it is amazing
and it really does give you an insight into the way people probably lived 50
or 60 thousand years ago.²
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