I'm considering the idea that the thinking subject in this case is best conceptualized as a vehicle for genes. In that case survival/prosperity has a completely different and even alien meaning from what we typically imagine. To give a trivial example: if I kill myself in order to save my children, I have succeeded and this is rational from the genetic point of view. It's not rational from a purely individualistic / hedonic point of view.

This is precisely my point. You attribute the capacity to reason to chemical molecules because their behavior seems purposeful. It does not occur to you that living entities may have goals and achieve those goals by using information processing means other than Reason(TM).

By the same logic, you could argue that tables are indeed rational to fall down, because otherwise they would fly into the sky.