Monogamy - Is It Necessary?

In his comment to my previous post, Rob wrote from Version 1.1 November 2002. I have extracted some parts below:

The tendency is for a male to use a female a number of times, and then to discard her. Therefore, in order to assess the degree of polygamous behavior of a certain man, we ought not to look at by how many females he is or has been bound into a permanent relationship at any given time, but solely at the number of different sexual partners he has ever had without getting married to..........

.............A man who concedes to the conditions brought about by a marriage typically signs over to his wife much of his wealth and financial independence. Because this kind of behavior does require irrationality, there is, under ordinary circumstances, a high degree of reluctance on the part of men to be available for marriage. A marriage is a victory for the female partner, rather than a male conquest. "

Rob's post takes a couple of reads in order to fully understand exactly what the post really means, but it raises even more questions, beyond what I initially posted about (ie. this phenomenon of the alpha male).

Does this view of male animal/human behaviour ignore the fact that humans have an emotional capacity, as well as a psychophysiological tendancy to find as many sexual partners in their life time? Are we discarding the fact that an Alpha Male too like the thought of ownership, of life time companionship or am I still lost in the idea of a fairytale?

Or is monogamy a cultural phenomenon that females have invented?