“Rational” in this context seems to mean “prone to reductive and simple explanations”.[1] But I have never heard of a scientific endeavor where people found out that things were more simple than they first hypothesized.

[1] And to be contrasted with those idiots who think that humans are “special” since they think that simple theories are not sufficient... or you know, maybe that organisms in general are complex machines or whatever you want to call it and that, yes, there are differences between a maggot, a bird and a human.