Solving Mysteries via DNA
As a geneticist at 23andMe, I combine my understanding of human prehistory and DNA variation to develop tools that help people answer one of the more fundamental questions we ask ourselves:
“Where am I from?”
It’s always fascinating and often surprising to answer that question, as the powerful stories in PBS’s series “Finding Your Roots” illustrate.
Intriguingly, the question “Where are you from?” has a precise meaning for many eastern Africans, as I learned when I was a Peace Corps volunteer in Kenya. I always respond to that question with “California,” where I have lived most of my life, rather than “England” where I was born. But unlike many Americans, Kenyans often respond to that question with a description of their ancestral origins — the place and its people. They may never have visited the place or people, but that is where they are “from.”
The answer to this question about our deeper ancestry allows us to connect with our ancestors of hundreds or thousands of years ago. If we go back far enough in human history the answer to the question “where are you from” is the same for everyone:
“We’re from Africa.”
But telling someone that “we are all from Africa” doesn’t really answer the question about a person’s origins.
Our DNA has no sense of where we live or where we were born, but it does point directly to our deeper ancestry and to where our ancestors were living over the last few thousand years. This power of DNA to answer questions about human prehistory is what drew me to genetics in the first place. Solving puzzles and mysteries has always fascinated me.
My passion for genetics is also rooted in Africa, in Kenya specifically, where I taught math and science as a Peace Corps volunteer 25 years ago. The mystery I came across there was in the faces, languages and diets as well as other cultural practices of the people I met. I couldn’t help being fascinated by the diversity. The tall, slender Nilotic-speaking Maasai of southwestern Kenya differ in so many ways from the Bantu-speaking Mijikenda who live on the eastern coast where I was teaching. I left Kenya mystified by the origins of that diversity. (Image: Joanna Mountain, teacher with the US Peace Corps in Kenya, showing off Takaungu High School to visiting dignitaries.)
Shortly after I returned home to California, a friend introduced me to a famous geneticist at Stanford University, Luca Cavalli-Sforza, who would give me the tools to solve that mystery. Cavalli-Sforza, who recently celebrated his 90th birthday, taught me the basics of DNA and the theories of population genetics. Together we poured over genetic data of peoples from all continents. Our goal was to discern the broad patterns of ancient human migrations.
I went on to earn my PhD in genetics, delving more deeply into the mysteries of human prehistory. Throughout my research I returned to focus on Africa, trying to understand the diversity that I had observed in Kenya. My research, conducted with collaborators from around the world, helped reveal the general shape of the history of African peoples over the last 100,000 years. We now believe that the ancestors of living peoples began to move from eastern or southern Africa into other parts of the continent by 75,000 years ago. This early spread within Africa explains the high level of genetic diversity in the continent today. The diversity among the people of Kenya that I noticed over two decades ago, which sparked my interest in the study of genetics, has been explained in part by migrations into eastern Africa of people speaking all the major languages of Africa. We’ve learned this by combining genetic information with archaeological and linguistic evidence.
In the same way that we can understand the diversity within Africa, we can understand the diversity of all living people by studying DNA, archaeology and languages. Both the origins of humankind in Africa and the patterns of subsequent migration within and outside of Africa are written in the DNA of living people. We all share a common history in Africa, but the DNA of people both within Africa and elsewhere has differentiated over time as people migrated across the planet, becoming, until the last few hundred years, more and more isolated from one another.
Map of human migrations over the last 100,000 years. L. L. Cavalli-Sforza and M. W. Feldman, Nature Genetics 33, 266 – 275 (2003).Now that we know how DNA aligns with prehistoric migrations, we can trace the DNA of individuals to northern Europe or Central Asia, South America or the Near East, western Africa or Oceania. That information about where DNA is from can, in turn, answer questions about our ancestors. Were they struggling to feed their children through hunting red deer in northern Europe, harvesting shellfish in southeastern Asia, raising alpacas in the highland plateaus of western South America, or digging for tubers in eastern Africa? DNA shows that some of us have ancestors who faced the challenge of survival using several of these strategies.
When Henry Louis Gates sits down with his guests and tells them their story of “where they are from” and explains their ancestry, it is a story that was written in their DNA many generations ago.
Joanna Mountain is a geneticist who is a consultant to the PBS series “Finding Your Roots,” and consulted previously on the PBS series “Faces of America.” Dr. Mountain completed her PhD in Genetics at Stanford University and has spent over 20 years studying human genetic diversity. Currently, she is Senior Director of Research at 23andMe, Inc.
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Comments
March 8, 2012 at 9:13 am
Professor Gates:
I have a grandmother, that was native american Indian but there are no records on her before she was 16 years old. And apparently, she did not share much of herself like where she came from or the name of the tribe in which she belonged to. Very mysterious.
Although I know my mother, I never knew my father. I know his name and he has passed on, but I never saw him face to face.
So I have some mystery as to my roots. And I was the only child conceived and lived that come from my mother and father, even though I do have one half sister that is estranged from my mother and I.
This used to be a source of sadness for me, I have since found peace about it, but I would really like to know…I think?! whether good or bad, it would just be nice to know my roots.
In my case, it may be better to have DNA testing done and try to go back beyond the generation that I have never met or have very little knowledge of.
Certainly, I came from someone…somewhere or I wouldn’t be here! That makes sense to me anyway.
Thank you for your episodes on PBS. I have enjoyed the journey that you take and the stories that have been told through the program!
Glenda Kuehn
March 19, 2012 at 4:01 pm
I have always been fascinated by the African relationship to Asia and India. Both cultures are very old, established and advanced. It is as if the Asian Continent contained a cultural element that allowed it to accelerate. Is the African connection viable as to the development of Asia & India?
March 23, 2012 at 9:34 am
HOW DO I SUBMIT MY DNA… ?
March 23, 2012 at 5:47 pm
Professor Gates, I am trying to do research on my family and it has been very tough through the years. A little bit about me I was born on an Island in the Caribbean called Trinidad as were my parents, grandparents, and some of my great grandparents, my family originally came over from India. As an adult I have so many questions and want to know so many things. I’ve watched your series on Genealogy and DNA and I find it amazing. Then I was told I don’t have a race Indians are a ethnic group, so I have to say that I am south asian… so here is my thing, I want to know more about my roots, I want to know what race I belong too besides the human race, I want to know the origins of my family and so on. I’m at a place now where I’m not sure where to go from here. I live in the US and would like to know your ideas and your suggestions? Also if there can be a project started for Indians in a research group, or something where I can participate it.
Thank You Kindly,
Alistair Sammy
March 25, 2012 at 10:16 pm
Great start of the shows. Many of commented on Facebook how much we enjoyed it. But we have a question:who was the young African -American
researcher in the Cory Booker/ John Lewis episode?
Thanks, and we’re all loking forward to next week’s episode.
March 26, 2012 at 10:28 am
After watching the show last night I am wondering how a person goes about getting the DNA test to help follow our own history. There are many questions I have about my Grandfather that I can seem to find. My mother has dementia and so what information I may gotten from her is gone now. Can you help me about the the test? How to go about getting it done and the cost and time involved? Thank you for such interesting shows. Enjoy them.
March 27, 2012 at 7:34 pm
i would like to know if i can get professor gates to find my roots ?
April 7, 2012 at 3:19 pm
As well as the majority of your viewers I am enjoying watching this show , than more than a show its like a piece of documentary . I
April 13, 2012 at 6:31 pm
I have been searching my roots for years now. The maternal branches of the Caruthers, Coleman, and Goff families of Madison and Crockett County, TN are much easier than my paternal Easterling side.
I cannot locate my father’s birth certificate, even though his military records say Kansas City, Mo., the vital statics bureau have no record of a George Quinton Easterling. Grandma Clara died in St. Louis and so did her mother Emma Ardry Means s I found lots of census info about them. James Easterling, my grandma’s husband, was not my dad’s father because he died in 1922 and George was born in 1929 or 1930.
April 20, 2012 at 4:02 pm
I found out yesterday there is a possibility that I am also Black Dutch. Investigating the history of the countries my ancestors came from is a lesson in history. History wasn’t my favorite subject in high school.
Also, I found through one of the episodes of “Finding Your Roots” that in the 100 years from the Emancipation Proclimation to Dr Martin Luther King’s I Have a Dream speech we took our treatment of the descendants of the released slaves to the level of making them feel like second-class citizens. That is WRONG!
I thank those that took part in any of the things that put Civil Rights back where it belonged: in the public arena.
April 26, 2012 at 11:33 am
In response to the program regarding knowing your roots, by Mr. Gates, Jr. ‘Question, how can Samual L. Jackson and Condilessa Rice, have black/white DNA and Downning, Jr have only white DNA’ Is it a myth that life began in Africa, if true, how can any person on this planet be ‘all White’. Can Mr. Gates connect the dots more correctly?
June 19, 2012 at 5:24 am
I would love to trace my family history on my father’s side but don’t know how to go about it. Would appreciate any help you can give me.