Over The Horizon

Assessing Our African Origins

The claim that humans originated in Africa has been supported by the findings of a PhD study on African ethnic groups, recently completed through Massey University. Elizabeth Watson, who was awarded a PhD in evolutionary genetics in May, spent nine months in Africa collecting blood and hair samples from 500 people to compile their genetic history. Her thesis was supervised by Professors David Penny and Mike Hendy, and she also worked with Professor Svante Paabo at Munich University in Germany, sequencing DNA and analysing data.

Watson used a region of the mitochondrial DNA (mtDNA) to analyse the genetic relationships between and within the ethnic groups' genetics. Generally a short region of DNA will be identical in all humans, but this locus has a high "substitution rate", which means that changes in the DNA bases accumulate quickly and can be useful for building a family tree of relationships within a species.

She then compared her findings to a database of genetics, gathered from other populations around the world.

"The most fascinating and exciting part of the study was the amount of diversity in African people. It is higher there than in any other continent," Watson says.

One ethnic group, the Turkana from Kenya, were the most diverse group of all African people, and therefore the most genetically diverse people in the world.

"In fact they are more diverse than the populations from around the world pooled together.

"That means that two individuals from the Turkana ethnic group have genetic make up which is more distinct from each other than say a European and an Asian person," she says.

Watson says the most likely explanation for such diversity is that Turkana people have the oldest history in the world, so the results suggest the origins of modern humans lie in East Africa.

No other research has studied in such depth the mtDNA in African people.

"It was very exciting that DNA could help us to understand the history of humankind," Watson says.

Her study of African ethnic groups also looked at what has happened within Africa, and the relationship between ethnic groups.

"Within the African groups, I found that groups all shared genetic elements, even though they may live thousands of kilometres apart. Of course some elements of people's genetic make-up were specific to a region. But the common elements meant they shared a similar history."

Watson plans to begin postdoctoral study through Massey University, and will continue studying questions raised in her thesis.