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Natural Selection Not The Only Process That Drives Evolution?

Orangutan mother and baby. Researchers identified fast evolving human genes by 
comparing our genome with those of other primates. (Credit: iStockphoto/Eric 

ScienceDaily (Jan. 28, 2009) — Why have some of our genes evolved rapidly? It 
is widely believed that Darwinian natural selection is responsible, but 
research led by a group at Uppsala University, suggests that a separate neutral 
(nonadaptive) process has made a significant contribution to human evolution.

Their results have been published January 27 in the journal PLoS Biology.

The researchers identified fast evolving human genes by comparing our genome 
with those of other primates. However, surprisingly, the patterns of molecular 
evolution in many of the genes they found did not contain signals of natural 
selection. Instead, their evidence suggests that a separate process known as 
BGC (biased gene conversion) has speeded up the rate of evolution in certain 
genes. This process increases the rate at which certain mutations spread 
through a population, regardless of whether they are beneficial or harmful.

"The research not only increases our understanding of human evolution, but also 
suggests that many techniques used by evolutionary biologists to detect 
selection may be flawed," says Matthew Webster of the Department of Medical 
Biochemistry and Microbiology at Uppsala University.

BGC is thought to be strongest in regions of high recombination, and can cause 
harmful mutations can spread through populations. The results lead to the 
provocative hypothesis that, rather than being the result of Darwinian 
selection for new adaptations, many of the genetic changes leading to 
human-specific characters may be the result of the fixation of harmful 
mutations. This contrasts the traditional Darwinistic view that they are the 
result of natural selection in favour of adaptive mutations.

Journal reference:

   1. Berglund J, Pollard KS, Webster MT. Hotspots of Biased Nucleotide 
Substitutions in Human Genes. PLoS Biology, 2009; 7 (1): e26 DOI: 

Adapted from materials provided by Uppsala University, via EurekAlert!, a 
service of AAAS.
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Uppsala University (2009, January 28). Natural Selection Not The Only Process 
That Drives Evolution?. ScienceDaily. Retrieved February 8, 2009, from 
http://www.sciencedaily.com­ /releases/2009/01/090126203207.htm

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