February 7, 2012

The Scientist: Prof. Spencer Wells Traces the Path of the Human Race

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The classic explorer, valiantly sails out to discover new lands, penciling in the blank edges of the map, may no longer hold a place in today’s society.  But, in this explorer’s absence emerges a modern adventurer who traverses the world, filling in not the missing parts of the globe, but rather the gaps in the map of human existence.

Spencer Wells, Frank H.T. Rhodes Class of ’56 Professor and Explorer-in-Residence at National Geographic and Director of the Genographic Project, has adventured to almost 80 countries, ridden ex-Soviet tanks in -70 degree temperatures in far-eastern Russia, traversed the worst part of the Sahara Desert in Chad and crossed mine fields in Bolivia, while on a quest to discover how the human race migrated the globe.

The goal of the ongoing Genographic project is to understand human origins and the genetic relations that are common to all people, according to Wells.

The project analyzes in particular the genes of remote populations along the Silk Road, from London to Mongolia, which is a region that has seen substantial human traffic throughout history. These populations often have relatively “old genes” according to Wells, which means that these groups have reproduced minimally with other populations since ancient times and thus their genes represent an older, purer version, similar to that of humanity’s oldest ancestors.

“The core of the science in this project is based on the work we do around the world with indigenous and traditional peoples,” Wells said. “Because they retain that geographic link back to their ancestors that most of us have lost that recently because our ancestors have moved around so much.”

By examining the number of genetic differences in populations and factoring in the normal rate of genetic mutation, he can determine how long a population has been in a certain region and through where it traveled to get there.

Unlike other academic geneticists, Wells gets to meet the people who give their samples to the Genographic project while in the field.  In doing so he gets to better understand the cultural patterns behind each sample, he said.

“It’s amazing being able to piece the story of human migration together by meeting the people who provided the clues,” Wells said.

In conducting the Genographic project, Wells found that humans are 99.9 percent genetically similar to each other.  The superficial differences between people are the result of small variation in only a few genes.

From the initial pool of genes, superficial changes have been those evolutionarily advantageous for survival in specific regions. For example, pale skin is necessary for sufficient vitamin D production in areas where there is little direct light and similarly, dark skin is advantageous in areas of relentless solar radiation. Other changes, such as hair type, can be attributed to sexual selection among individual populations, Wells said.The genetic homogeneity of Homo sapiens can be contributed to a near extinction event 70,000 years ago. At this time, there were only a few thousand humans alive in the world, all of them living in Africa.

When compared with the rest of the large apes, who have between four and 10 times more within-species diversity than humans, people are significantly more similar than outward appearances would suggest.

“I think this message of people being much more closely connected genetically than we might suspect by looking at surface features is an important social message that to me can’t be overstated.”

Original Author: Shauntle Barley