Dr. Spencer Wells on Collecting Genetic Data Around the World

Description: Wells uses the latest microbiological techniques to accomplish his genographic mission.

Question: How do you go about collecting data?

Transcript: You know, we’re building on the work of many, many people, particularly the work of the man who was my post doctoral advisor at Stanford, Lucca Cavalli-Sforza who really kind of created the field of human population genetics, starting back in the 1950s, studying blood groups and other so called classical polymorphisms, these are protein variance and cell surfaces like the blood groups and, you know, so studying things that were studyable in those days before the DNA era before, you know, molecular genetics really came along and he started to ask questions like, you know, does this genetic information tell us something about how human populations are related and yes it did but it was kinda vague.  And it was really only with the era of DNA sequencing which came about in the 1980s that people could start to get out some of the details of this. 

Question: Where do you get blood samples?

Transcript: Yeah and so, you know, the question that has been asked since that first, you know, era back in the 1950s and even before was just an open ended one, you know, so what is the pattern of variation look like and, you know, where does it lead us.  We’re starting in the present in effect so we’re kind of answering the question in reverse, we’re searching for origins in people alive today and so there’s some theoretical framework built into it.  But basically what you’re looking at are shared genetic variance.  So if you share a genetic marker with someone, these are changes that occur from time to time as DNA’s been copied to pass on through the generations, if you share one of these markers, you are part of the same lineage of the human family and by looking at the pattern of shared markers all over the world we can trace further and further back into time.  So we place even to ever deeper branches on the human family tree and so we wanna take as wide a survey of human variation as possible.  Ideally we would sample every person alive today and sequence their entire genome, now that’s, you know, literally impossible, it’d be way too expensive.  We have, you know, to spend the money on other perhaps more important things but in effect we wanna take as broad of a survey of human diversity as possible.  So we sample people from around the globe and just ask what do the patterns look like and in particular we ask where are those deepest branches on the tree.  So where is humanity most diverse, where has it been accumulating variation for the longest and that leads us back to Africa and the story that the DNA tells us is that we all came out of Africa very recently and, you know, it’s nothing new to say that we are an African species.  Darwin said that 130 years ago in The Descent of Man, he wrote that we most likely came from Africa because our nearest cousins the apes appeared in Africa first and so we most likely appeared there as well.  The key is to give a time and so was it 23 million years ago when apes appear in the fossil record, now as recently as 60,000 years ago.  Every human alive on the planet was living in Africa and it’s only in the last 60,000 years that people started to scatter around the rest of the world and so the idea is you sample as many people as possible, the more the better.  2000 is good, 20,000 is better, 200,000 is even better and you ask where did their lineages trace back to.

Recorded on: 5/22/08