Natural Selection Influencing Recent Human Evolution
The most detailed analysis to date of how humans
differ from one another at the DNA level shows strong evidence that natural
selection has shaped the recent evolution of our species, according to
researchers.
In a study published in the Oct. 20 issue of the journal Nature, Cornell scientists analyzed 11,624 genes, comparing how genes vary not only among 39 humans but also between the humans and a chimpanzee, whose DNA is 99 percent identical to humans.
The comparisons within and between species suggest that about 9 percent of genes that show some variability within humans or differences between humans and chimpanzees have evolved too rapidly to be explained simply by chance. The study suggests that positive Darwinian natural selection -- in which some forms of a gene are favored because they increase the probability of survival or reproduction -- is responsible for the increased rate of evolution. Since genes are blueprints for proteins, positive selection causes changes in the amino acid sequence of the protein for which the gene codes.
"Our study suggests that natural selection has played an important role in patterning the human genome," said the paper's lead author, Carlos Bustamante, assistant professor of biological statistics and computational biology at Cornell.
My favorite perception of irony focuses on the hypocrites who say, “you can’t rely on mathematics or biological sciences” -- and go merrily about their lives relying on modern industrial products and medicine entirely founded on what they don’t believe.
"We have a long way to go before we can predict from looking at sequences, which mutations in which genes and under which environmental conditions can ultimately lead to disease. This is a first step in identifying the classes of genes that appear to be particularly vulnerable to these types of changes," said Bustamante.
A team from Celera initiated the project and sequenced more than 20,000 genes in 39 humans and a chimpanzee. By comparing the DNA sequences of the 39 human subjects across the 20,000 genes, the Celera researchers identified DNA sites in the genome where individuals in the sample differed from one another. The chimpanzee sequence was then used to identify which form of the gene was the original ancestral form and which was the derived or new type. The original goal of the project was to identify novel amino acid variants that could then be tested for association with human disease in subsequent studies. The Cornell researchers became involved at the analysis stage in order to make predictions about what types of changes are most likely to be functionally important.
A fine example of research work in one area made available for other researchers to investigate.
Posted: Wed - October 26, 2005 at 07:18 AM