Genetic mutation may have allowed early humans to migrate throughout Africa

Sep 19, 2012

A genetic mutation that occurred thousands of years ago might be the answer to how early humans were able to move from central Africa and across the continent in what has been called "the great expansion," according to new research from Wake Forest Baptist Medical Center.

By analyzing variation patterns in different populations around the world, three teams of scientists from Wake Forest Baptist, Johns Hopkins University School of Medicine and the University of Washington School of Medicine, Seattle, demonstrated that a critical genetic variant arose in a key on , known as the fatty acid desaturase cluster or FADS, more than 85,000 years ago. This variation would have allowed early humans to convert plant-based (PUFAs) to brain PUFAs necessary for increased brain size, complexity and function. The FADS cluster plays a critical role in determining how effectively medium-chain PUFAs found in plants are converted to the long-chain PUFAs found in the brain.

This research is published online today in .

Archeological and suggest that homo sapiens appeared approximately 180,000 years ago, but stayed in one location around bodies of water in central Africa for almost 100,000 years. Senior author Floyd H. "Ski" Chilton, Ph.D., professor of physiology and pharmacology and director of the Center for Botanical Lipids and Inflammatory Disease Prevention at Wake Forest Baptist, and others have hypothesized that this location was critical, in part, because early humans needed large amounts of the long-chain PUFA docosahexaenoic acid (DHA), which is found in shellfish and fish, to support complex .

"This may have kept early humans tethered to the water in central Africa where there was a constant food source of DHA," Chilton said. "There has been considerable debate on how early humans were able to obtain sufficient DHA necessary to maintain and complexity. It's 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.'"

Once this trait arose, the study shows that it was under intense selective pressure and thus rapidly spread throughout the population of the entire 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 that exist in contemporary populations," said Joshua M. Akey, Ph.D., lead scientist at the University of Washington.

This conversion meant that didn't have to rely on just one food source, fish, for brain growth and development. This may have been particularly important because the genetic variant arose before organized hunting and fishing could have provided more reliable sources of long-chain PUFAs, Akey said.

To investigate the evolutionary forces shaping patterns of variation in the FADS gene cluster in geographically diverse populations, the researchers analyzed 1,092 individuals representing 15 different human populations that were sequenced as part of the 1000 Genome Project and 1,043 individuals from 52 populations from the Human Genome Diversity Panel database. They focused on the FADS cluster because they knew those genes code for the enzymatic steps in long-chain PUFA synthesis that are the least efficient.

Chilton said the findings were possible because of the collaboration of internationally recognized scientists from three distinct and diverse disciplines – fatty acid biochemistry (Wake Forest Baptist), statistical genetics (Johns Hopkins) and population genetics (University of Washington). This new information builds on Chilton's 2011 research findings published in BMC Genetics that showed how people of African descent have a much higher frequency of the gene variants that convert plant-based medium-chain omega-6 PUFAs found in cooking oils and processed foods to long-chain PUFAs that cause inflammation. Compared to Caucasians, African Americans in the United States have much higher rates of hypertension, type 2 diabetes, stroke, coronary heart disease and certain types of cancer. "The current observation provides another important clue as to why diverse racial and ethnic populations likely respond differently to the modern western diet," Chilton said.

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jonnyboy
Sep 19, 2012
This comment has been removed by a moderator.
JVK
1.2 / 5 (17) Sep 19, 2012
A mutation? Who decided to call a critical genetic variation that arose in a key gene cluster more than 85,000 years ago, which allowed early humans to convert plant-based polyunsaturated fatty acids as required for or increased brain size, complexity, and function a mutation? It is clearly the result of a nutrient chemical-driven epigenetic effect on intracellular signaling and stochastic gene expression that enables adaptive evolution via ecological, social, neurogenic, and socio-cognitive niche construction constrained by pheromones that control reproduction.

Calling it a mutation reminds me of how foolish theories about random mutations have maintained their foothold in the literature only because they are so often repeated. See for comparison: Kohl, J.V. (2012) Human pheromones and food odors: epigenetic influences on the socioaffective nature of evolved behaviors. Socioaffective Neuroscience & Psychology, 2: 17338. http://dx.doi.org...i0.17338
Parsec
5 / 5 (11) Sep 20, 2012
It is clearly the result of a nutrient chemical-driven epigenetic effect on intracellular signaling and stochastic gene expression that enables adaptive evolution via ecological, social, neurogenic, and socio-cognitive niche construction constrained by pheromones that control reproduction.


Really? You have some evidence for this? The research indicated the changes were a mutation in the genes, i.e. the actual coding sequence was modified, indicating a base change in the DNA, not an epigenetic effect.

Unless you have evidence for your suggestion, its just wild eyed speculation, far from clear.
la7dfa
1 / 5 (4) Sep 20, 2012
Much of the migrations have followed the coastline, especially from Africa to India and beyond. There it was access to shell, crabs etc.
Homo Erectus arrived in England some 700.000 years ago. Its a bit strange if a needed mutation occur in erectus (?), then disappear when we became humans. But its not the first time in evolution genes has been disabled for a long period. :)
Anda
2.5 / 5 (4) Sep 20, 2012
I don't discuss the mutation but i'm sceptical about their hypotesis that complex human brain function was a consequence of a fish diet... never heard such a theory.
Squirrel
2 / 5 (2) Sep 20, 2012
The paper's abstract with a link to the open access pdf is here http://www.ploson....0044926
JVK
1 / 5 (6) Sep 20, 2012
It is clearly the result of a nutrient chemical-driven epigenetic effect on intracellular signaling and stochastic gene expression that enables adaptive evolution via ecological, social, neurogenic, and socio-cognitive niche construction constrained by pheromones that control reproduction.


Really? You have some evidence for this? The research indicated the changes were a mutation in the genes, i.e. the actual coding sequence was modified, indicating a base change in the DNA, not an epigenetic effect.

Unless you have evidence for your suggestion, its just wild eyed speculation, far from clear.


I linked to the evidence. How would a mutation cause adaptive evolution? Is their any evidence for that?
Kohl, J.V. (2012) Human pheromones and food odors: epigenetic influences on the socioaffective nature of evolved behaviors. Socioaffective Neuroscience & Psychology, 2: 17338. http://dx.doi.org...i0.17338