Saturday, July 21, 2007

Research Points to Single Origin of Humans

(HealthDay News) -- All humans originated from a single point in Africa and migrated across the world, say British researchers at the University of Cambridge.

Previously, there were two theories on the origin of humans. One theory said that all humans originated in Africa. The second theory said that different populations of humans evolved from different areas of the world.

But in a new study published in the July 19 issue of Nature, researchers say they have proven the single origin of humans theory by combining studies of global genetic variations in humans with skull measurements across the world.

The researchers studied genetic diversity of human populations around the world and measured more than 6,000 skulls from across the globe, kept in academic collections.

They found that losses in genetic diversity the farther a population is from Africa are mirrored by losses in variation in physical attributes.

Variation in the physical attributes of the skulls was highest among the sample from southeastern Africa, and it decreased at the same rate as the genetic data the farther the skull was away from Africa.

"The origin of anatomically modern humans has been the focus of much heated debate. Our genetic research shows the further modern humans have migrated from Africa, the more genetic diversity has been lost within a population," lead researcher Andrea Manica, from the university's department of zoology, said in a prepared statement.

"However, some have used skull data to argue that modern humans originated in multiple spots around the world. We have combined our genetic data with new measurements of a large sample of skulls to show definitively that modern humans originated from a single area in sub-Saharan Africa," Manica said.

The decrease in genetic diversity in populations farther from Africa was likely a result of "bottlenecks" -- events that temporarily reduced populations during human migration.
The researchers attempted to use their data to find non-African origins for modern humans, testing the theory of multiple origins.

"To test the alternative theory for the origin of modern humans, we tried to find an additional, non-African origin. We found this just did not work. Our findings show that humans originated in a single area in Sub-Saharan Africa," co-researcher Francois Balloux said in a prepared statement.

More information
The U.S. National Human Genome Research Institute has more about genetic variation.

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