Navigation Links
Geography and history shape genetic differences in humans

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
Public Library of Science

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:
(Date:5/16/2016)... NEW YORK , May 16, 2016   ... authentication solutions, today announced the opening of an IoT ... to strengthen and expand the development of embedded ... provides an unprecedented level of convenience and security with ... to authenticate one,s identity aside from DNA. EyeLock,s platform ...
(Date:4/28/2016)... Sweden , April 28, 2016 First ... M (139.9), up 966% compared with the first quarter of 2015 ... profit totaled SEK 589.1 M (loss: 18.8) and the operating margin ... 7.12 (loss: 0.32) Cash flow from operations was SEK ... The 2016 revenue guidance is unchanged, SEK 7,000-8,500 M. ...
(Date:4/15/2016)... Research and Markets has announced ... 2016-2020,"  report to their offering.  , ... global gait biometrics market is expected to grow ... 2016-2020. Gait analysis generates multiple variables ... to compute factors that are not or cannot ...
Breaking Biology News(10 mins):
(Date:6/27/2016)... ... June 27, 2016 , ... Cancer experts from Austria, Hungary, ... be a new and helpful biomarker for malignant pleural mesothelioma. Surviving Mesothelioma has ... it now. , Biomarkers are components in the blood, tissue or body ...
(Date:6/27/2016)... , June 27, 2016  Liquid Biotech ... announced the funding of a Sponsored Research Agreement ... circulating tumor cells (CTCs) from cancer patients.  The ... in CTC levels correlate with clinical outcomes in ... These data will then be employed to support ...
(Date:6/24/2016)... ... June 24, 2016 , ... While the majority of commercial spectrophotometers ... 5000 and the 6000i models are higher end machines that use the more unconventional ... spectrophotometer’s light beam from the bottom of the cuvette holder. , FireflySci has ...
(Date:6/23/2016)... 2016   Boston Biomedical , an industry ... to target cancer stemness pathways, announced that its ... Drug Designation from the U.S. Food and Drug ... including gastroesophageal junction (GEJ) cancer. Napabucasin is an ... cancer stemness pathways by targeting STAT3, and is ...
Breaking Biology Technology: