Under the system of marriage, many women were forced to marry men with whom they did not wish to mate. This is because women had been previously accustomed to mating with only the top dog, most dominant and high-status men. Under the regime of marriage, each of those men could only take one wife, leaving them inaccessible sexually (at least legitimately) to most women. This clearly impeded the wired, Darwinian mating strategy of the human female, whereby women prefer to mate only with the best they can find who will agree to mate with them. Of course there were benefits for women in marriage as well: a woman received the undivided support, attention and parental investment of one man, rather than a portion to be shared with co-wives. But that material benefit, as helpful as it was, likely could not in itself balance out the sexual attractions women had for high status, dominant men. And so it was that women developed a dual strategy: find the best unmarried man to marry who will invest in her children, while finding the best married man to mate with to provide strong genes – the cuckolding strategy.
That is not quite exact. Many kind of primates do not have that kind of "mating strategy", and also its just simplistic to assume that without considering the culture of the individuals. In my country I have seen natives with VERY WEIRD beliefs and behaviour related to mating, and I would say that culture who offers the determinant factor in human behaviour.
If we are going to consider only the biologic factor, I think both men and women are meant to have many partners, as many as possible.
I have seen an article recently written by an Professor at my university, and he basicly concludes that humans have a big size of testicles due to competition in producing sperm. Mainly, big primates like gorilas, who compete by size of the body, and have small testicles(smaller than humans) because they take control of a family and do not allow other males to mate with any of his females. On smaller chimps and others primates, the females have many partners, so they compete with sperm production, therefore, the ones with big testicles will pass their genes ahead. So if we consider that human have an average size of testicles, being big, but not as big as those kind of chimps, you can conclude that humans would be a mid term between the two of them.
Also, I dont think "atraction" is a huge factor on long term relationships. The real emotional spark will be over after a few years dont matter what. What he or she does after that is what determines how "quality" someone can be, and it is the difference between a divorce and a successfull marriage.
