Any time you want to think about some aspect of human behavior, it may be a good idea to start at the simplest known point.  If you could boil human existence down to one word, I think it would be survival.  This is not strictly limited to humans, but humans are my main focus.

  At this point, it applies to anything living.  Stay alive at least long enough to reproduce.  It's the survival of the species, and within that, survival of the individual.

  As a human, you survive as an individual, find a mate, reproduce, and then do what is needed to make sure your offspring survive until they can ensure their own survival.  This is the core of human existence.

  Humans are separated into males and females, and it is the combined efforts of the two which succeed in the continuation of the species.  Each gender plays its part both physically and in terms of behavior.  No one gender is better than the other, overall.  They are each simply better at certain things, by virtue of this core design.

  If you want to do justice to either gender, you must view it as a counterpart to the other.  They are two sides of the same coin.  The goal is continuance of the species, and each gender compensates for what the other lacks in succeeding.  Understanding this, you can more easily understand the individual genders.

  There is a duality.  Males are physical, agressive, dominating, practical.  Females are emotional, nurturing, harmonic, intuitive.  Some of these things alone may not seem like good things on the surface, but they are there to serve the greater purpose.

  While the female focuses on caring for the offspring, the male focuses on creating an environment that allows the female to do so.

  The general qualities of a human female personality make it the ideal gender for being the primary care-giver for a child.  The general qualities of a human male personality make it the ideal gender for being the protector and provider for the female.

  Keep in mind that I am talking about the core drives of the genders.  In modern society, these qualities are not as obviously necessary, because we have advanced enough to make certain achievments easier.  When you think about the depths of human behavior, you have to look at humans at their most simple.

  The modern day battle of the sexes has no place here.  This is not about what a gender is capable of doing.  Follow advancement and evolution long enough into the future, and the gender reach a point where there are no distinctions of any kind.  Each gender adapts to more and more towards true equality of being, and reproduction is no longer a matter of sex.

  But for now, even though certain gender rolls are no longer a matter of necessity, that core distinction still has its influence.