As a man, I feel it my duty to cast my own thoughts into this arena. (And also as a man, it is also my solemn obligation to chuckle ever so slightly, at the pronunciation of the word "duty".) Continuing onward!

You have to remember that males are programmed a certain way, and we are so programmed for a reason. Back in the caveman days, and heck, even up until the last hundred years or so, the ratio of infants born v.s. infants born that survived to adulthood and reproduction was very highly stacked in favor of those born. So many more infants and children died than those who lived to maturity, the number was like 5 to 1 in the time of Shakespeare. (Correct me if I am wrong on the numbers, anyone. Feel free, I like to be accurate.) The idea was that if a male reproduces with many females, instead of just one, it meant more offspring and therefore the species survives. So we are programmed to want to mate with anything and everything we see that we find attractive. (And anyone who has ever suffered from the condition known as "Beer Goggles" knows just how broad that definition may be.)

Therefore, we are, on the instinctual level, in the animal brain, programmed not necessarily to be polygamous, per se, if we are going by the human definition of having multiple spouses. The scientific (or zoological) definition means mating with multiple partners, and in that case, it can be said that we men are programmed to be just so. However, that doesn't end the debate.

Oh no, this goes on, sports fans, because it actually gets a little complex at this point, because NOW we get to the patterns of human behavior, which is far less simple, depending on viewpoint, than mere biology. The best viewpoint is always to not take one side, but consider all perspectives., when it comes to anything scientific or pseudo-scientific. (An eclectic approach.)

Some men are polygamous in certain times of their lives. Some are at all times. Some of us like to be fooling around with multiple partners (at different times of course), because some of us just do that. Many of us happen to be very happy in our committed relationships, thank you, and wouldn't ever think of straying off the reservation, so to speak, because the essential wrong that doing so entails is distasteful. And just plain wrong. That doesn't mean we don't think about it, it just means we don't do it. The Kicker? Many women are the same way. Desires vs. actual practice are worlds apart. So if I see that uber attractive blond out in, let's say the mall, just because I think "She is HOT!" doesn't necessarily mean I do anything about it, for fear of not only reprisal in the form of numerous insults of my physical person in the form of flying objects, but also of hurting somebody I dearly care about.

In Summation: Are Men Polygamous? In thought and in instinct, according to our programming. It's our nature. In practice? Not so much. Many of us humans have an instinct towards staying with one partner for a period of time, be it for a few weeks, to a few months, or for the majority of our existence. If anything, we would be mostly guilty of serial monogamy.