Gene networks in living organisms are part of a dynamical system whose output make up the traits of organisms and determine reproductive fitness. One of the roles that such networks play is to respond to variability in the environment. Because organisms are the product of past evolution, we expect that evolution will generally increase organismal fitness, but this is subject to some constraints and historical effects. In this talk, I will discuss models of fluctuating environments where the output of the gene network determines fitness. I compare the outcome of optimal control models with evolved gene networks and discuss how the networks parameters evolve.