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.
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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