Thanks for your quick replies. Yes we are agreed in those two points. I'm going to try something that may come off as a little crude, but here goes:

Point 1: If every act or process that helps me is to be called rational, then having a diëtician for a parent is rational. Point 2: The term rational implies involvement of the 'ratio', of thinking. Point 3: No rational thinking, or any thinking at all, is involved in acquiring one's parents. Even adaptive parents tend to acquire their child, not the other way around. Conclusion; Something is wrong with saying that everything that leads to the attainment of a goal is rational.

Perhaps another term should be used for things that help achieve goals but that do not involve thinking, let alone rational or logically sound thinking. This is important because thought is often overstated in the prevalence with which it occurs, and also in the causal weight that is attached to it. Thought is not omnipresent, and thought is often of minor importance in accurately explaining a social phenomenon.