Where Is Your Family Tree Rooted?
At some time in the distant past, the ancestors of all six billion of us may have lived in Africa
Human Migration Through the Millennia
Your family tree may look quite different than you expected. That is, you might well be related to the queen of England — but through a common ancestor who lived millennia ago.
In pursuit of such knowledge, National Geographic and IBM Corp. have undertaken an ambitious, five-year, $40 million project to trace the migration of human beings and their cultures over the thousands of years of human existence. The massive research project will involve the collection, identification and computer analysis of about 100,000 DNA sample — pre-historic, historic and contemporary.
Questions to answer
“We want to learn the why of history,” said Spencer Wells, National Geographic’s director of the Genographic Project. “Why did people move? Why did these people look a little bit like those people? Why did they speak the same language or a different language? We want to place the genetic information in the context of history and anthropology.”
DNA Traces the Paths of Humans
Last year, University of Pennsylvania anthropologist Theodore Schurr, head of the Genographic Project’s North American branch, took DNA samples from members of the Seaconke Wampanoag, a Native American tribe that once thrived in the northeastern United States.
Members of the Seaconke wanted to know more about their genealogy but were limited by a lack of written records, says Michael Markley, the tribe’s chairman. He saw a write-up on the project in National Geographic magazine and sought out the chance to get involved and learn more about the distant past of his people.
Archaeology suggests that the Seaconke’s ancestors came from Siberia many centuries ago. The DNA of surviving members could eventually reveal more precisely when their ancestors crossed the land bridge from Asia into North America, how quickly they traversed the continent, where they might have lived before reaching the eastern coast, and with which tribes they are most closely related.
Schurr says he and his colleagues want to sample DNA from members of indigenous groups because they are less “admixed” than the typical person living in the United States. Researchers need the help of people such as Micronesians or Kalahari bushmen because more is already known about how long they’ve occupied their homelands and where they lived before, thanks to linguistics, archaeology and history.
Groups that tend to intermarry also provide clearer branches on the human family tree. Those with more diverse ancestry may carry bits of genetic material from those branches that scientists don’t yet know how to identify and interpret.
In the 1950s. Italian geneticist Luigi Cavalli-Sforza used blood types to determine relationship between the people of the world’s continents. After moving to Stanford University in the early 1970s, he started gathering genetic clues. We all carry many harmless copying errors, called mutations, in our DNA, and how many of these we share with someone else tells something of how closely we’re related.
The first bit of DNA studied was called mitochondrial DNA, which is carried was eggs but not sperm, thereby following maternal lines. By comparing copying errors in volunteers from around the world and estimating how long it takes them to accumulate, researchers estimate that human beings share common ancestors who lived in Africa several thousand years ago. Similar studies involving the Y chromosome follow male lines and also lead to an African origin.
Results of the study
DNA analysis has already shown that skin color and other traits we associate with race are much more superficial than previously thought and emerged only in the last few thousands of years, Schurr says,”The important thing to remind people of is, despite our differences, we share a common heritage.”
- genographic 基因地理的 : using genetics to study human migration over time
- genetic 遺傳(學)的
- anthropology 人類學
- genealogy 家譜學
- archaeology 考古學
- Micronesian 麥克羅尼西亞人
- Kalahari bushmen 喀拉哈里沙漠布西曼族
- linguistics 語言學
- mitochondrial 線粒體的
- millennium : a period of 1000 years
- undertake : to do or begin to do something, especially something that will be difficult
- thrive : to grow, develop or be successful
- indigenous : naturally existing in a location rather than arriving from another place
- mutation : the way in which genes change and produce permanent differences
- superficial : not complete and involving only the most obvious things