The findings, based on data gathered from hundreds of museum specimens of dogs and from blood samples of volunteered live dogs, offer a new explanation for the sudden, rapid rise of new species found in the fossil record. They also help explain the variability in appearance among individual members of a species, such as the length of the nose in different breeds of domestic dogs.

The findings will appear in an upcoming issue of the Proceedings of the National Academy of Sciences and are available online.

"We're offering an explanation for a lot of different components of evolution, one that goes against the central dogma that currently explains how certain aspects of evolution take place," said Dr. Harold "Skip" Garner, professor of biochemistry and internal medicine at UT Southwestern and one of the authors of the study, which involved only small, non-invasive blood draws from dogs by licensed veterinarians.

The chemical units that make up an organism's DNA, or genetic code, are abbreviated with the letters A, C, T and G. Strings of these letters spell out the genetic instructions needed to carry out all of life's functions.

Most scientists agree that over very long periods of time, mutations in the genetic code are responsible for driving evolutionary changes in species. One widely accepted hypothesis is that random, so-called single-point mutations - a change from one letter to another among the billions of letters contained in the code - minutely but inexorably change an organism's appearance.

UT Southwestern scientists, however, believe the single-point mutation process is much too slow and happens much too infrequently to account for the rapid rise of new species found in the fossil rec
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Contact: Amanda Siegfried
Amanda.siegfried@utsouthwestern.edu
214-648-3404
UT Southwestern Medical Center
13-Dec-2004