For another, among those tribes and nations who were constantly at war with each other, there would inevitably be a scarcity of men in proportion to the women.
Before humankind began to gather in clans and tribes, what passed for courtship was likely a raid on a distant group of humans that resulted in the capture of a woman who was forced to participate against her will in an instant marriage.
True courtship practices between the sexes did not exist to any great extent, and feelings of fondness or affection, if they entered into the equation at all, resulted from compatibility extended over a period of time.
As the human species became more mannered and various religious rites began to be observed, young men and women sought to make themselves attractive to non-family members of the opposite sex who resided near them in the same village or series of villages.
In those tribes or societies where women were in short supply, a man would want to be assured of at least one woman whom he would not have to share.
Some social historians argue that children presented the greatest incentive toward monogamy.
Among many primitive tribal peoples even today, a marriage is not solemnized until the first child is born, and if no child is born the man is at liberty to leave the woman.
Biologists have long noted that among the lower animals the natural instinct is to protect the young and supply food for their subsistence.
Many anthropologists and social historians have expressed their views that early humans practiced polygamy (one man with several women in the marriage union) or polyandry (several men with one woman).
In either case, quite likely the women involved in the union probably had been captives before they were wives.
Although these marital circumstances may have existed for quite some time among early humans, there are a number of reasons why neither polygamy nor polyandry could have survived as universal or general practices.
For one thing, some societies practiced infanticide, killing primarily female infants, and creating a scarcity of women.