Harvard University scientists have identified a virtual “speed limit” on the rate of molecular evolution in organisms, and the magic number appears to be six mutations per genome per generation — a rate of change beyond which species run the strong risk of extinction as their genomes lose stability.
By modeling the stability of proteins required for an organism’s survival, Eugene Shakhnovich and his colleagues have discovered this essential thermodynamic limit on a species’ rate of evolution. Their discovery, published this week in the Proceedings of the National Academy of Sciences, draws a crucial connection between the physical properties of genetic material and the survival fitness of an entire organism.
“While mathematical genetics research has brought about some remarkable discoveries over the years, these approaches always failed to connect the dots between the reproductive fitness of organisms and the molecular properties of the proteins encoded by their genomes,” says Shakhnovich, professor of chemistry and chemical biology in Harvard’s Faculty of Arts and Sciences. “We’ve made an important step toward finally bridging the gap between macroscopic and microscopic biology.”
Eugene Shakhnovich: ‘We’ve made an important step toward finally bridging the gap between macroscopic and microscopic biology.’ 
