See also... http://news.sciencemag.org/2009/04/chimps-trade-meat-chance-sex
Marriage is not natural to humans, it is a social norm created to produce more effective armies, driven by the sexual dominance nature of primates. Consider the following fundamental motivations for marriage, and then adapt a more reasonable solution this long established custom. We are at the top of the food chain, and must use our ability to reason, to overcome the many unreasonable animal like behaviors we still perpetuate.
Originally, humans lived in communities where children were cared by that community, behavior similar to that displayed by a troop of apes. Early human troops were based on a male dominance certain rituals to gain sexual rights within the troupe.
Non-dominant males have clandestine relations with available females in the tribe. The genetic dominance of the alpha male is subject to the wishes of the females. Alpha dominance is in constant threat from the competition of younger males who work to gain the favor of the females in the troop. Females make all real choices for the troop, and they benefit from this need by males to display dominance. In Chimpanzee troops males will gather to hunt monkeys, and are 10 times more effective than lions at hunting. After a kill is made the meat is divided up among the males and then shared with the females for favors. The tradition of the engagement ring could well be seen is an offshoot of this early primate tradition. Marriage has no part in the sexual social structure of the troop.
Confrontations between one troop to another were based on this sexual first cause. In the case of Chimps, just as humans, they can and will, annihilate neighbor Chimp troops.
Over time the human troop became a tribe, and a tribe became a nation. The sexual social basis of the troop, tribe or nation, has remained the same throughout our human evolution, a culture based on this male ritual for dominance. The competitive nature of man or primate has not changed, today males continue to do battle and bring booty back to the women of our troop.
It is only size density, that effects the transition from troupe, tribe, and nation. At some point in that evolution, it became apparent that it would be best to apportion one women exclusively to each single male. Law and order within the troop could be best kept if there was less infighting. Males could go fight wars, and children would be cared for by their spouse without the concern she would take another man in his absence. With the potential longer absences from the tribe, battles became wars lasting years.
Religions evolved, and strict social norms were created requiring the fidelity of marriage. This was not an exclusive rule, for it was not until recently did a dominant human male called "Lord" would have sexual rights over all females of his troop, or reign.
Nomadic societies or tribes would have no choice but to take the entire family into battle. Established agrarian societies needed a well defined concept of marriage in order to defend the established community. Men would go to war, and the women would stay to tend the farm and children. In order to ease the horror of war, males would return with booty, to be apportioned to a nations citizens. It is these early agrarian societies that will become the cradle of civilization, Babylon and Egypt are the extension of the troop, based on a modified sexual rite of the dominance of the alpha male, subject to the wishes of the females. The appropriate religion would follow to enforce the traditions.
Social behavior is clearly dominated by the fact that we did evolve from animals. Over time we developed wedding customs to maximize the communities ability to succeed in this male to male sex combat. It is more effective to portion out women through marriage, as it reduces conflict between the males of a community. This also frees the males to do battle with other communities for plunder and booty, return home and have the assurance women folk remain chase. This was an important fundamental aspect of Chivalry.
This arrangement is what created the behavior of our modern society. Females' sense of self became dependent on a male providers, and a good male was seen as a good provider, to both family and the community. Although today norms are changing, a female, either by genetics, or social conditioning, still expects the opposite sex to provide.
Males have a confused sense of community, their sexual nature sees no issue with having sex with women of a neighboring community. They are sexually attracted to many females regardless of community. Women tend to be more clannish, driven to defend the troupe or community. Women look to family first, and community second, with the role of provider and protector role assigned to men.
Of course this is a gradient, there are a variety of forms of this behavior. There are males that are as females and females that are as males. One would hope that we will move away from a society of sexual dominance to one of parity of sexes, based on a rational view of our sexual behavior.
These are generalizations, yet we have formed an archetypical concept of man and woman. We see "Man" as providing protection and order to the tribe, woman as subservient, and responsible for home and child care. This traditional image of man and woman is changing quickly. The future will bring us a new way of dealing with our male-female relation, it will hopefully be more true to reason, and more agreeable to ourselves.
Let us consider God in all this. We are making a transition from this male sexual dominance social type to a more equal relation between man and woman, at the same time we centralize populations into a one world order. At the precise point when we will no longer need this long established tradition of marriage, we have established a one dominant order on our world.
An interesting and related text from the Gnostic Gospel of Tomas
114) Simon Peter said to them, "Mary should leave us, for females are not worthy of life." Jesus said, "See, I am going to attract her to make her male so that she too might become a living spirit that resembles you males. For every female (element) that makes itself male will enter the kingdom of heaven."
Does this indicate the goal of sexual equality, or a precise character flaw?