As mentioned above, crisis often brings out the desire for a sexual release. For any crisis, there are two times this can happen: during, and after.

Please note: I am attempt to take a very objective view of this and thus it may seem a bit cold and heartless. Furthermore, this is purely speculative - I am neither a psychologist nor have I been in or near any such crisis.

I don't want to die a virgin

Just before and during a crisis when death seems imminent, it is often the wish for the last minutes to be pleasurable. Once again, there are to possible 'programmed' reasons - one, is the last minutes being pleasurable (as mentioned above), the other is for the chance that the female will survive (women and children first?) in which case the act has possibility of preserving some of the genes of the male.

After a crisis where many die the population decline may trigger the need to procreate - especially among the survivors and heroes of the crisis. In theory, these individuals are the most suited to the environment. Picture, if you will, a hypothetical land where every 25 years half the population is wiped out. For those who remain, the group (be it people, monkeys, lions, or what have you) must have children if it is to survive the next crisis. With many animals, it is often the case that the loss of the offspring will bring the females into heat again. While this may not be exactly the case with humans, it is not impossible that some of that biological drive still exists.