Man by nature needs to propagate, therefore the sex drive of the
male seemed to be more pressuring on them. Look at animals, they
see a female, if urge comes, they mate - normally the male force it
on them, or have to tame them... So by right, when man sees a
potential 'prey' to loosen up their dick, they entered into
primitive thinking, like beast. 
... Just that when man is intelligent, undergo civilization,
undergo religions and teaching, have emotions that beast don't have
- jealousy, etc, people don't do it with every female they want.
But when the situations seemed right (guys feel woman is screwable,
woman feels guy is horny and gets horny) - the beast within may try
to take over and ONS will happen within a flash. 
Do anything you wish, just that don't never regret what you had
done. 
