This seems to be a question that I used to see on Yahoo Answers.
Men have a brain and they also have an unbrain. The brain is the higher functioning portion of their anatomy but the unbrain often has more influence on their behavior. You asked about men, so that is who I am focusing on. There would probably be some similar comparison that could be applicable to the unmen but now is not the time or place for that.
When boys hit puberty, their unbrain kicks in, and the damage that they do is an equation that uses the muliple of the parental guidance that they have inculcated within their social psyche, times the number of pg and above rated movies, times the number of hours that they have spent playing Women in the Congo while drinking Real Coke less the number of hours they sleep. This factor is divided by the number of girls , two years younger than they are, who live within a 60 min walk of their best friends house. If their best friend has three semi beautiful sisters, these calculation would be bypassed and the equation of the more time they spend in their best friends house would be directly equated to the increasing influence of the unbrain on their behavior. If they have absolutely no social skills that this would negate any influence of unmen on their behavior and they will end up playing video games and attending gambling casinos for entertainment until at least the age of 30.
By the time they are 30, they have started to figure out that their brains must be used in order to meet the needs of the unbrain. Knowing this, they can hold it together long enough to convince certain unmales much younger or older than themselves, that there is hope for a satisfying life with them. But, because our culture is so screwed up this is not the case in at least 50 to 75% of the relationships and so you end up with the circumstance that your question derives from.
I hope this is helpful. I usually charge $200/hour for advice of this nature.