It simply isn't true, for example, that being big is in general better for fitness than being small except when there are effects of interacting variables; or that flying slow and high is in general better for fitness than flying fast and low except when there are effects of interacting variables; or that being monogamous is in general better for fitness than being polygamous... except when there are effects of interacting variables... It's not that the underlying generalizations are there but imperceptible in the ambient noise.
