From an evolutionary perspective, every living thing has two basic goals: survive and reproduce, in that order. It's helpful to keep these goals in mind when considering how human behavior develops over time. This powerful drive to ensure that our genes make it into the next generation provides insight into such complex issues as monogamy.
We've all heard the conventional wisdom that women prefer monogamy (only one mate at a time), while men gravitate toward promiscuity (as many mates as you can get). But is there evidence to back this up? And, if true, why would the optimal mating system of one sex be different from that of the other? To answer these questions, let's consider the benefits of a monogamous relationship.
Scientists have been studying mating patterns in animals for centuries, and monogamy is definitely rare; only 3 to 5 percent of Earth's mammals practice some form of monogamy [source: National Science Foundation]. Recent insight into the question of monogamy in humans comes from Dr. Aaron E. Carroll and Dr. Rachel C. Vreeman of the Indiana University Medical Center. Carroll and Vreeman argue that being in a long-term monogamous relationship leads to a steep decline in libido among both men and women, but that the decline is more severe in women [source: Carroll and Vreeman]. They point out that loss of interest in sex among women can lead to the death of a sex life, which isn't good for anyone from an evolutionary point of view.
There is also recent evidence to support the notion that men are more inclined to promiscuity, while women fall slightly more on the monogamous side of things [source: Wlodarski]. An important detail in this study is that it takes into account social and cultural factors that inevitably influence the behavior of both men and women to show that humans operate on a sexual continuum, with monogamy on one end and promiscuity on the other. All it takes is the right set of environmental (or social or cultural) conditions to push us in one direction or the other [source: Wlodarski].
Each example of monogamy in animals may have evolved for specific reasons, but the general scientific consensus is that animals form more lasting relationships when it improves their chances of having more successful offspring. Humans provide a perfect case study. Having both parents cooperate in the care of a newborn — presumably within the context of a blissful and exclusive relationship — makes sense when you consider the utter helplessness of human babies.
However, if stronger offspring is the driving force behind monogamy in humans, it doesn't make sense that only females would be "hardwired" for it. Not surprisingly, there is evidence to support the claim that monogamy in human males is advantageous too, perhaps to ensure the safety of his offspring or simply because making a commitment is the only way he's going to get any reproductive action [sources: Opie; Lukas and Clutton-Brock].
The point is that, for both sexes, these mating behaviors may change based on environmental factors in order to achieve our ultimate goal of getting our genes into the next generation. Men and women are both hardwired for this flexibility, though our circuits may not always follow the same path.