what history lost, genetics tries to recover
Africa is the cradle of humanity, which is why it's the most exciting place to study the early days of modern human evolution.
We've long assumed that Africa is home to the widest genetic diversity in humans. After all, it's our ancestral home and it only makes sense that as we spread throughout the world, the genetic variation for each culture and society eventually narrowed. This is why the recent headline about a 10 year study by a team of scientists showing this was indeed the case didn't raise many eyebrows.
Of course, this isn't what the study actually set out to test. Instead, using basic evolutionary principles as their guide, the team tried to add more details to a rather murky map of human migration across the world and pinpoint the genetic relationships between 121 African, 60 non-African and four African-American populations.
Looking at patterns in 1,327 insertion and deletion markers in over 3,000 collected DNA samples, scientists found a group of 14 "ancestral population clusters" with similar language, ethnicity and culture. According to Dr. Sarah Tishkoff, the study's lead scientist, this is a big departure from how genetic ancestry was studied in the past. Researchers would take DNA from a small group of Africans and assume they were a good sample for the continent's genetic make-up.
However, as the study shows, that's not actually the case and there's so much genetic variety in African populations you can't take a random sample of several individuals and use it for genomics research. Ultimately the data will be used to help conduct better studies on gene and disease relationships as well as better track down the ancestral history of human populations.
Societies which preserved their language and traditions for hundreds of years and seem pretty uniform to an outside observer, could have a vibrant genetic history which mixes genes from numerous populations around them, or even groups of ancient nomads who once came their way.
Dr. Tishkoff's team ran into a very similar situation with the Masai people of Kenya who extensively mixed with Ethiopian populations while maintaining the same lifestyles and linguistic traditions since time immemorial. It seems that when we use genes to take a peek into the history of humanity, we find that it's a lot more dynamic and complex than we think.
See: Tishkoff, S., et al., (2009). The Genetic Structure and History of Africans and African Americans Science DOI: 10.1126/science.1172257
