The multi-species comparison published in Science also yielded surprising results about the rate at which chromosomal evolution occurs. Based on an analysis that included a computer-generated reconstruction of the genomes of long-extinct mammals, researchers found the rate of chromosomal evolution among mammals dramatically accelerated following the extinction of the dinosaurs about 65 million years ago.
Before the sudden demise of dinosaurs and many other types of animals, which is thought to have resulted from a massive comet or asteroid striking Earth, mammals shared fairly similar body plans and also fairly similar genomes. Researchers speculate that the mass extinction opened new ecological niches for mammals, spurring their diversification and the emergence of new mammalian orders. This situation would have facilitated opportunities for the isolation of mammals into more distinct breeding groups, speeding the development of species-specific chromosomes.
"This study has revealed many hidden secrets on the nature and timing of genome evolution in mammals, and it demonstrates how the study of basic evolutionary processes can lead to new insights into the origin of human diseases," said Dr. Lewin, who is director of the Institute of Genomic Biology at the University of Illinois.