Why is it that in the Jewish history, a man was allowed to marry a few wives (e.g. our Patriach Jacob), and the women were severely punished if they had committed adultery? I am not saying that adultery is right, G-d forbid. But why were the men allowed to have a few wives and a woman only one husband?
Ultimately we have to realize that this is what G-d prescribed for us. This is discussed in the portion of the Torah dealing with the adulterer and the adulteress, Numbers 5:11-31.
In terms of trying to understand this rationally, I’ll be happy to share with you the way that I understand it, but this is only my personal perception. Please feel free to challenge it.
First of all, we must make 2 observations. It is very rare, if at all, to find a female rapist. Also, the vast majority of prostitutes are female. I believe that the reason for this is as follows. There is a major difference between the sexual attitudes of males and females. Women, generally, are not interested in having relations with someone for whom they have no emotional bond. Once they have entered a relationship, they give it their all; it isn’t only the body that they are offering to the relationship, it is their entire being. Men, on the other hand, have a much more physical interest in the relationship. As unpleasant as this may seem, the typical male will have relations with anyone, given the opportunity. This is why there are male rapists and not female rapists. This is also why men will pay prostitutes for sex, yet few women have a desire to do so. Consequently, once a marriage has been entered, it is a violation of the relationship for a woman to commit adultery, and both parties are considered adulterers. In fact, if a single man sleeps with a married woman, both he and the married woman are deserving of death! On the other hand, a married man will not be considered in violation of this bond by having relations with a single woman, or by having more than one wife.
I know that this portrays a very low image for men in general, and, as a matter of fact, we do find in the Torah that women are spiritually and emotionally superior to men. However, please understand that this is on the most base, carnal, level. Through a life of Torah study and performance of Mitzvos, men can elevate themselves. It seems to me, that this is why men have more Mitzvah obligations than women.