Share

Humans may have faced extinction

Human beings may have had a brush with extinction 70 000 years ago, an extensive genetic study suggests.

The human population at that time was reduced to small isolated groups in Africa, apparently because of drought, according to an analysis. The report notes that a separate study by researchers at Stanford University estimated the number of early humans may have shrunk as low as 2 000 before numbers began to expand again in the early Stone Age.

"This study illustrates the extraordinary power of genetics to reveal insights into some of the key events in our species' history," Spencer Wells, National Geographic Society explorer in residence, said in a statement. "Tiny bands of early humans, forced apart by harsh environmental conditions, coming back from the brink to reunite and populate the world. Truly an epic drama, written in our DNA."

Wells is director of the Genographic Project, launched in 2005 to study anthropology using genetics. The report was published in the American Journal of Human Genetics.

Previous studies using mitochondrial DNA - which is passed down through mothers - have traced modern humans to a single 'mitochondrial Eve', who lived in Africa about 200 000 years ago.

The migrations of humans out of Africa to populate the rest of the world appear to have begun about 60 000 years ago, but little has been known about humans between Eve and that dispersal.

How the study was done
The new study looks at the mitochondrial DNA of the Khoi and San people in South Africa which appear to have diverged from other people between 90 000 and 150 000 years ago.

The researchers led by Doron Behar of Rambam Medical Centre in Haifa, Israel and Saharon Rosset of IBM T.J. Watson Research Centre and Tel Aviv University concluded that humans separated into small populations prior to the Stone Age, when they came back together and began to increase in numbers and spread to other areas.

Eastern Africa experienced a series of severe droughts between 135 000 and 90 000 years ago and the researchers said this climatological shift may have contributed to the population changes, dividing into small, isolated groups which developed independently.

Climate almost led to human extinction
Palaeontologist Meave Leakey, a Genographic adviser, commented, "Who would have thought that as recently as 70 000 years ago, extremes of climate had reduced our population to such small numbers that we were on the very edge of extinction."

Today more than 6.6 billion people inhabit the globe, according to the US Census Bureau. The research was funded by the National Geographic Society, IBM, the Waitt Family Foundation, the Seaver Family Foundation, Family Tree DNA and Arizona Research Labs. – (Sapa)

April 2008

Read more:
Nano-scale structures made from DNA
DNA shows people less alike

We live in a world where facts and fiction get blurred
Who we choose to trust can have a profound impact on our lives. Join thousands of devoted South Africans who look to News24 to bring them news they can trust every day. As we celebrate 25 years, become a News24 subscriber as we strive to keep you informed, inspired and empowered.
Join News24 today
heading
description
username
Show Comments ()
Editorial feedback and complaints

Contact the public editor with feedback for our journalists, complaints, queries or suggestions about articles on News24.

LEARN MORE