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Modern humans began in southwest Africa. That's according to a new genetic study of Africans, the largest ever. The 10-year research project examined blood samples from people all over the African continent. Scientists say it will tell us more about the history of our species, and it could help them better understand how to treat certain diseases.
NPR's Christopher Joyce reports.
CHRISTOPHER JOYCE: This was a monumental task, according to the scientists who undertook it. Traveling by road to some of Africa's most remote places, the scientific team drew blood from 121 different groups all over the continent. Sarah Tishkoff from the University of Pennsylvania was in charge of the project.
Ms. SARAH TISHKOFF (University of Pennsylvania): I think the most remarkable finding is the extensive amount of genetic diversity not only within but among African populations. And one of the key points of the study is that there is no single African population that is representative of the diversity present on the continent.
JOYCE: By looking at how many changes have accumulated in the DNA of various groups, geneticists can determine how long they've lived apart from each other. Scientists can also tease out information about when and where different groups migrated over thousands of years' time.
The team says their genetic map shows that modern humans probably originated near the South African-Namibian border, and their last waypoint before migrating out of Africa was Northeastern Africa near the Red Sea.
The scientists also compared the African genes to those of African-Americans and concluded that on average, African-Americans inherited about 71 percent of their DNA from ancestors in Western Africa and about 13 percent from Europeans.
Tishkoff says scientists can better understand inherited diseases and how to treat them by studying variations in the genes of different African groups.
Ms. TISHKOFF: Like resistance to malaria infection. Some of these variants could also cause disease, and they may be geographically restricted to certain regions. So the only way we're going to even find them is by looking at these different populations.
JOYCE: The research appears in this week's issue of the journal, Science.
Christopher Joyce, NPR News.
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