April Flowers for redOrbit.com Your Universe Online

Thousands of years ago, a genetic mutation occurred which might be the answer to how early humans were able to move from central Africa and across the continent. This movement has been called the great expansion.

Three teams of researchers, from Wake Forest Baptist Medical Center, Johns Hopkins University School of Medicine and University of Washington School of Medicine, have analyzed genetic sequence variation patterns in different populations around the world. Their research, published this week in the online journal PLoS One, demonstrates that about 85,000 years ago, a critical genetic variant arose in a key gene cluster on chromosome 11, known as the fatty acid desaturase cluster (FADS).

This genetic variant would have allowed humans to convert plant-based polyunsaturated fatty acids (PUFAs) to brain PUFAs. The long-chain of PUFAs found in the brain are necessary for increased brain size, complexity and function, and the FADS cluster plays a critical role in determining how effectively medium-chain PUFAs in plants are converted.

According to archeological and genetic studies, Homo sapiens appeared approximately 180,000 years ago. For almost 100,000 years, our early ancestors tended to stay in one location close to bodies of water in central Africa. Scientists have hypothesized that this location was critical because early humans needed large amounts of the long-chain PUFA docosahexaenoic acid (DHA) commonly found in fish and shellfish in order to support complex brain function.

This may have kept early humans tethered to the water in central Africa where there was a constant food source of DHA, explained Dr. Floyd Chilton, director of the Center for Botanical Lipids and Inflammatory Disease Prevention at Wake Forest Baptist.

There has been considerable debate on how early humans were able to obtain sufficient DHA necessary to maintain brain size and complexity. Its amazing to think we may have uncovered the region of genetic variation that arose about the time that early humans moved out of this central region in what has been called the great expansion.

Under the intense pressure of natural section, this new trait was able to spread rapidly throughout the entire Homo sapiens population on the African continent.

The power of genetics continually impresses me, and I find it remarkable that we can make inferences about things that happened tens of thousands of years ago by studying patterns of genetic variation that exist in contemporary populations, said Dr. Joshua M. Akey from the University of Washington.

The most important result of this conversion was that humans no longer had to rely on just one food source, fish, for brain growth and development. This was particularly important because the genetic variant arose before organized hunting and fishing could have provided more reliable sources of long-chain PUFAs.

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New Studies On Genetic Variations Offer Insights Into Origins Of Man