Humans more similar than different
Ethnicity may be as good a guide to genetic susceptibilities as testing.
20 December 2002
TOM CLARKE


95 percent of all genetic variation exists within populations.
© USDA



Inuit or Basque, Laotian or Pashtun: we're much more similar than we are different, says the most detailed analysis of human genetic variation to date1.

When it comes to sensitivity to drugs or diseases, the analysis also suggests that a person's account of their ethnic origin is almost as reliable an indicator as intrusive genetic tests.

Around 95% of all genetic variation exists within populations. Just 3 to 5% of variation occurs between different ones, the study finds. "When the world is such a fractious place, it's reassuring to think about our similarities," comments Lynn Jorde, a population geneticist at the University of Utah in Salt Lake City.

Comparing nearly 400 genetic markers from over 1,000 people representing 52 different cultures and nationalities, Noah Rosenberg at the University of Southern California and colleagues searched for patterns of similarities.

Traditionally, researchers have divided DNA samples according to geographical location - North America and Africa say - or language, and looked for differences. Instead, Rosenberg's team "took an honest look at lots of DNA," says Jorde.

Previous studies relying on 20 or 30 markers have only found strong evidence of genetic variation between very isolated populations. The latest high-resolution analysis "allows us to answer questions people couldn't before," says study co-author Jonathan Pritchard, of the University of Chicago.

It reveals that humans fall into six broad genetic groups, corresponding to people living in Eurasia, the Americas, sub-Saharan Africa, East Asia and Oceania.

Identifying these groupings could be good news for medicine. Many genes for susceptibility to particular diseases, drugs and vaccines vary between populations.


The human genome has provided markers for comparison.
© Nature



In the absence of evidence for genetic differences between populations, some researchers had begun to argue that simply asking patients their ethnic or geographic origin is not enough to determine their likely genetic background and that testing is required instead2.

For everyday medical purposes, intrusive genetic tests probably won't be necessary argues Pritchard. "The correlation between self-reported ethnicity and genetic clustering is very strong," he says. "Doctors can ask what ethnicity you are and go with that," he says.

Like previous analyses, Rosenberg's team identified big differences between very isolated populations such as pygmy tribes in Africa. They also highlighted new ones: the Kalash people of northern Pakistan, previously thought to be of East Asian origin, are genetically more similar to those from Europe or the Middle East, they found.


References
Rosenberg, N. A. et al. Genetic structure of human populations. Science, 298, 2381 - 2385, (2002). |Homepage|
Wilson, J. F. et al. Population genetic structure of variable drug response. Nature Genetics, 29, 265 - 269, (2001). |Article|


http://www.nature.com/nsu/021216/021216-13.html