Abstract

One of the most striking patterns of evolution is its uneven tempo across the tree of life. Whereas some traits and lineages diversify rapidly, others appear to remain inert over millions of years. But, why is this so? What allows some features to achieve evolutionary overdrive, and why do some traits appear to straddle evolution’s slow lane? I explore this question by focusing on one of evolution’s key architects: behavior. I illustrate how organisms are not the passive targets of selection; rather, through behavior, they can be the agents of selection. Using Caribbean Anolis lizards as a model system, I reveal the signatures of behavior at both micro- and macroevolutionary scales, and illustrate the constraints on this phenomenon. Behavior can slow or hasten evolution and, on occasion, it does both simultaneously.