They reported that, compared to lower primates, humans possess a distinctive variant in a regulatory segment of the prodynorphin gene, which is a precursor molecule for a range of regulatory proteins called "neuropeptides." This variant increases the amount of prodynorphin produced in the brain.
While the researchers do not understand the physiological implications of the activated PDYN gene in humans, they said their finding offers an important and intriguing piece of a puzzle of the mechanism by which humans evolved from lower primates.
They also said that the discovery of this first evolutionarily selected gene is likely only the beginning of a new pathway of exploring how the pressure of natural selection influenced evolution of other genes.
They also said their finding demonstrates how evolution can act more efficiently to alter the regulatory segments, or "promoters," that determine genes' activity, rather than on the gene segment that determines the structure of the protein it produces. Such regulatory alteration, they said, can more readily generate variability than the hit-or-miss mutations that alter protein structure and function.
Proteins constitute the molecular machinery of the cell, for example, catalyzing the multitude of chemical reactions in the cell. DNA genes constitute the blueprints for such proteins, with the regulatory segments of these genes determining how actively the genes churn out proteins.
The researchers published their findings in the December 2005 issue of the Public Library of Science. They were Gregory Wray and David Goldstein of Duke University; Matthew Rockma