Navigation Links
Geography and history shape genetic differences in humans
Date:6/5/2009

New research indicates that natural selection may shape the human genome much more slowly than previously thought. Other factors -- the movements of humans within and among continents, the expansions and contractions of populations, and the vagaries of genetic chance have heavily influenced the distribution of genetic variations in populations around the world. The study, conducted by a team from the Howard Hughes Medical Institute, the University of Chicago, the University of California and Stanford University, is published June 5 in the open-access journal PLoS Genetics.

In recent years, geneticists have identified a handful of genes that have helped human populations adapt to new environments within just a few thousand yearsa strikingly short timescale in evolutionary terms. However, the team found that for most genes, it can take at least 50,000-100,000 years for natural selection to spread favorable traits through a human population. According to their analysis, gene variants tend to be distributed throughout the world in patterns that reflect ancient population movements and other aspects of population history. "We don't think that selection has been strong enough to completely fine-tune the adaptation of individual human populations to their local environments," says co-author Jonathan Pritchard. "In addition to selection, demographic history -- how populations have moved around -- has exerted a strong effect on the distribution of variants."

To determine whether the frequency of a particular variant resulted from natural selection, Pritchard and his colleagues compared the distribution of variants in parts of the genome that affect the structure and regulation of proteins to the distribution of variants in parts of the genome that do not affect proteins. Since these neutral parts of the genome are less likely to be affected by natural selection, they reasoned that studying variants in these regions should reflect the demographic history of populations.

The researchers found that many previously identified genetic signals of selection may have been created by historical and demographic factors rather than by selection. When the team compared closely related populations they found few large genetic differences. If the individual populations' environments were exerting strong selective pressure, such differences should have been apparent.

Selection may still be occurring in many regions of the genome, says Pritchard. But if so, it is exerting a moderate effect on many genes that together influence a biological characteristic. "We don't know enough yet about the genetics of most human traits to be able to pick out all of the relevant variation," says Pritchard. "As functional studies go forward, people will start figuring out the phenotypes that are associated with selective signals," says lead author Graham Coop. "That will be very important, because then we can figure out what selection pressures underlie these episodes of natural selection."

But even with further research, much will remain unknown about the processes that have resulted in human traits. In particular, Pritchard and Coop urge great caution in trying to link selection with complex characteristics like intelligence. "We're in the infancy of trying to understand what signals of selection are telling us," says Coop, "so it's a very long jump to attribute cultural features and group characteristics to selection."


'/>"/>

Contact: Catriona Silvey
csilvey@plos.org
Public Library of Science
Source:Eurekalert

Related biology news :

1. Mixing genomics and geography yields insights into life and environment
2. Biogeography, changing climates and niche evolution
3. Surprising discovery from first large-scale analysis of biodiversity and biogeography of viruses
4. Prehistoric aesthetics explains snail biogeography puzzle
5. History of hyperactivity off-base, says researcher
6. Penn Medicine honored for its historic role in the history of microbiology
7. Tiny differences in our genes help shed light on the big picture of human history
8. DOE makes largest Danforth Campus research award in history
9. Study of protein structures reveals key events in evolutionary history
10. Chantix side effects no worse with depression history
11. NJIT history professor receives national endowment for humanities
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:3/27/2017)... , March 27, 2017  Catholic Health ... and Management Systems Society (HIMSS) Analytics for achieving ... Adoption Model sm . In addition, CHS previously ... U.S. hospitals using an electronic medical record (EMR). ... its high level of EMR usage in an ...
(Date:3/24/2017)... , Mar 24, 2017 Research and ... Access System Market Analysis & Trends - Industry Forecast to 2025" ... ... to grow at a CAGR of around 15.1% over the next ... This industry report analyzes the market estimates and forecasts for all ...
(Date:3/23/2017)... Mar. 23, 2017 Research and Markets has ... Analysis & Trends - Industry Forecast to 2025" report to ... ... a CAGR of around 8.8% over the next decade to reach ... analyzes the market estimates and forecasts for all the given segments ...
Breaking Biology News(10 mins):
(Date:9/21/2017)... , ... September 21, 2017 , ... ... neon green this month, the response was swift and efficient thanks to the ... ). RRWQG is made up of more than 50 stakeholders, including officials from ...
(Date:9/20/2017)... ... September 20, 2017 , ... Cybrexa Therapeutics , ... to the role of chief scientific officer. In this role, Dr. Paralkar will ... president and CEO, Per Hellsund. , “I was impressed with Cybrexa’s revolutionary technology ...
(Date:9/20/2017)... ... September 20, 2017 , ... ... study examining the effects of exoskeleton-assisted walking on gait parameters and neuromuscular ... article, "Neuromechanical adaptations during a robotic powered exoskeleton assisted walking session" (doi:10.1080.10790268.2017.1314900) ...
(Date:9/19/2017)... ... September 19, 2017 , ... ... the most dangerous step of sample prep for metals digestion—the addition of acids ... at an affordable price. The system is ideal for any laboratory performing their ...
Breaking Biology Technology: