April 16, 2009

Nat’l Geographic Expert Traces Human Origins

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“Where did we come from, and how did we get to where we live today?”
So read the flyer distributed by The Cornell Center for Comparative and Population Genomics promoting yesterday’s lecture by Spencer Wells, PhD., director of the Genographic Project at the National Geographic Society.
There were few empty seats in Call Auditorium in Kennedy Hall yesterday evening, where Ithaca residents and members of the Cornell community gathered to hear Wells speak.
“It’s great to see such a high turnout, especially on tax day,” Wells said. “I’m glad all of you aren’t off doing strange things with teabags.”
Wells’ talk focused on the question of human origin and the question of the human journey. The purpose of the Genographic Project, a five-year endeavor started in April of 2005, is to “explain the patterns of human diversity that we see throughout the world,” according to Wells, by mapping patterns of human migration from a common African Homo sapiens ancestor.
“But how different are we?” Wells asked.
According to Wells, humans are about 99.9 percent identical at the genetic level. The one-in-a-thousand sequence mutations are what make individuals unique. These genetic markers can be used to trace “family trees” of ancestral origin.
“Different regional populations carry distinct markers that can be traced back to a common African ancestor,” Wells said.
The longest branches in the human “family tree” are found in African populations. This means, Wells said, “Africans have been accumulating these genetic changes for longer than any other group.”
Addressing the question of origin, Wells tracked humans — “people we would recognize as resembling us if they were sitting in the third row” — to a common African ancestor.
“The most recent common ancestor was a man who walked the plains of Africa between 60 and 90 thousand years ago,” Wells said. “From an evolutionary perspective, that’s the blink of an eye.”
To answer its research question of the human journey, the Genographic Project is sequencing DNA samples from indigenous populations and from the general public in order to track migration patterns from an original locus by specific genetic markers.
The focus thus far has been on indigenous peoples who have lived in the same place for a long period of time.
“They retain that link to the past and to their ancestors,” Wells said. “They still display genetic patterns that many of us have lost.”
DNA from 50,000 indigenous volunteers have been sequenced thus far. This number represents about half of the Genographic project’s target sample size.
Wells also stressed the importance of public participation.
“We didn’t want to limit it to the story of the world’s indigenous peoples — it’s the story of everyone.”
Members of the public wishing to take part in the study can purchase a gene sequencing kit for $110.95 from genographic.nationalgeographic.com.
To this point, 300,000 people from 130 countries have submitted their DNA to the project.
Profits from kit sales fund Genographic research and support the Legacy Fund, an organization created to educate and protect indigenous peoples and cultures.
Legacy Fund projects include the documentation of the dying practice of oral poetry in Sierra Leone, the preservation of traditional weaving patterns in Gaza, and the categorization of native plants and their uses in Ecuador. The Legacy Fund is also working to revitalize traditional language being lost to mass migration in Tajikistan, where a dying tongue was once the “Lingua Franca” of the silk road.
“We’re going through a period of cultural mass extinction at this point,” Wells said. “We’re losing a language every two weeks.”
Wells focused on the impact of abrupt and severe climate changes on patterns of human habitation in his explanation of the human journey.
According to Wells, humans left sub-Saharan Africa about 45,000 years ago, migrating to the Middle East.
“How did people actually cross the Sahara 40 to 50 thousand years ago, across this sand sea?”
Wells referred to paleoclimatological evidence for a mechanism he referred to as “the Climate Pump.”
The earth’s precessional rotations determine where in Africa the monsoon rains will fall, sometimes causing them to be pushed farther north.
Evidence suggests that 40,000 to 50,000 years ago, the Sahara used to be grassland, allowing early humans, still in the hunter-gatherer phase of civilization, to cross into the Middle East.
“These results are really leading us to reevaluate where people came from,” Wells said. “More and more it’s starting to look like these climatic shifts are determining where people moved and when.”
Even today, Wells argued, climate controls human migration patterns.
“We like to think that we are above being controlled by the climate these days, but that’s not necessarily the case,” he said.
“Climatologists believe that storms like Hurricane Katrina will increase in frequency and intensity.”
Wells noted that Katrina displaced thousands of people from their homes, many of whom have not returned. The prediction, based on the past, is that sudden and major climate changes will determine the movement of populations.
One woman spoke at length during the question-and-answer portion of the lecture about the rights of indigenous peoples. Wells reiterated the systematic and sensitive way that his project was promoted in indigenous areas.
“The whole issue of privacy is one that we thought about long and hard before we initiated the Project,” he responded. “We feel that we’ve been very open and collaborative about this with indigenous communities. We are not trying to exploit.”
Wells believes strongly in the importance of the Genographic Project.
“Think about the pharmaceuticals that might be prescribed by your physicians,” he said. “Over half of them can be tracked back to traditional plant sources. How many potential cures for cancer or aids might we be missing out on? [This is] an important reason to preserve this knowledge.”­­­­­