Sorry for giving this such a vague title, as it is slightly difficult to explain.
The debate about differences in behaviour (say between the genders) is normally characterised as nature vs. nurture - that is some kind of physical difference in the structure or chemicals in someones brain vs. society teaching people to act in that way.
On the other hand, there is another explanation that could be important in certain circumstances and the best word that I can think to describe this is situational - that is that the two genders may be completely different situations.
Take for example the fact that it is harder for women to have children at an older age then it is for men. Let's suppose we observe a greater desire among women to settle down at any earlier age. As an alternative to the brain chemistry explanation or the social expectations, this difference in behaviour could also be explained as a "situational" difference - that is, the women are in a different situation then the men due to having a shorter period of time in which they can have children.
Is there a formal term for this kind of explanation?