I think of the process of rationality as using evidence to (on average) improve behavior in the sense of using behaviors that produce better results. Evolution is a strange example, in that this process of improvement is not deliberative. It has no model, even metaphorically, that is deeper than "this gene contributes to genetic fitness". It is incapable of processing any evidence other than the actual level of reproductive success of a genetic organism, and even then it only manages to update gene frequencies in the right direction, not nearly the rationally optimal amount (or even as close as deliberative human rationality gets). It is this small improvement in response to evidence that I consider rational (at a very low level). The fact that we can trace the causal steps of the evidence (reproductive fitness) to the improvement at a deep physical level matters only as much as the fact that in principle we could do the same with the causal steps of evidence I observe influencing the neurons in my brain which implements my rationality.