Evolution Turns on a Moving Target: Beneficial Mutations May Be Temporary

A University of Michigan study reexamines the Neutral Theory, finding that beneficial mutations may be more common than assumed yet rarely fix in changing environments. The researchers propose Adaptive Tracking with Antagonistic Pleiotropy: organisms constantly chase shifting conditions, so most advantageous mutations are temporary. Yeast experiments show fewer beneficial mutations fix when environments vary, suggesting evolution is driven by moving targets rather than perfect adaptation; results may extend beyond microbes but need data from multicellular organisms.