As soon as a woman gets pregnant she has just signed on for a 20 year tour of duty taking care of the resulting child. Her goal, going back millions of years, is to help that baby survive. For a woman pregnancy carries an extremely high cost. Furthermore, the woman s mind and body also know, instinctively at some level, that a baby needs two people to survive. Women are therefore designed to wait for a strong commitment prior to getting pregnant.
Many men seem to have little or no such programming.
This basic anatomical difference, by itself, leads to rather strong differences in priorities between men and women. In addition, men and women clearly have different programming in other parts of their brains. For example, men are much more aggressive, in general, than women, while women tend to be much more nurturing. Men are more individualistic, while women are more social. Men tend to rely more on rational thought, while women rely more on feelings.