You apparently assume that if women are to form multiple attachments, there will be more attachment opportunities for all men, not just those in the upper tiers of attractiveness. Yet in reality, we see some contrary evidence, in that when women become more promiscuous, the additional amount of sex taking place is not at all distributed randomly or equally across all categories of men; instead, those in the upper tiers of attractiveness get the overwhelming part of it. (I know that this is not equivalent to what you have in mind, but I do think that there is enough similarity to provide at least some relevant evidence.)
This does seem to be the case. F. Roger Devlin makes a rather bold statement of this argument in this essay (though I dislike his conservative political slant and certain biased terms; also, ignore his criticism of feminist discourse on sexual violence, because it is massively lower quality that everything else he writes and riddled with errors):
Once monogamy is abolished, no restriction is placed on a woman’s choices.
Hence, all women choose the same few men. If Casanova had 132 lovers it is because 132 different women chose him. Such men acquire harems, not because they are predators, but because they happen to be attractive. The problem is not so much male immorality as simple arithmetic; it is obviously impossible for every woman to have exclusive possession of the most attractive man. If women want to mate simply as their natural drives impel them, they must, rationally speaking, be willing to share their mate with others.But, of course, women’s attitude about this situation is not especially rational. They expect their alpha man to “commit.” Woman’s complaining about men’s failure to commit, one suspects, means merely that they are unable to get a highly attractive man to commit to them; rather as if an ordinary man were to propose to Helen of Troy and complain of her refusal by saying “women don’t want to get married.”
Casanova may have had 132 lovers, but most or all of them weren't long-term relationships. There's an upper-limit to the number of serious romantic relationships one person can maintain at one time, and it's certainly less than ten and probably closer to five (the highest I've heard of is four). Furthermore, I've pointed out elsewhere that historically, harems are not devised by women.
If women and men maintain approximately equal numbers of relationships (which they seem to, in the poly community), then the most attractive partners available to you will be...
Many of us are familiar with Donald Rumsfeld's famous (and surprisingly useful) taxonomy of knowledge:
But this taxonomy (as originally described) omits an important fourth category: unknown knowns, the things we don't know that we know. This category encompasses the knowledge of many of our own personal beliefs, what I call unquestioned defaults. For example, most modern Americans possess the unquestioned default belief that they have some moral responsibility for their own freely-chosen actions. In the twelfth century, most Europeans possessed the unquestioned default belief that the Christian god existed. And so on. These unknown knowns are largely the products of a particular culture; they require homogeneity of belief to remain unknown.
By definition, we are each completely ignorant of our own unknown knowns. So even when our culture gives us a fairly accurate map of the territory, we'll never notice the Mercator projection's effect. Unless it's pointed out to us or we find contradictory evidence, that is. A single observation can be all it takes, if you're paying attention and asking questions. The answers might not change your mind, but you'll still come out of the process with more knowledge than you went in with.
When I was eighteen I went on a date with a girl I'll call Emma, who conscientiously informed me that she already had two boyfriends: she was, she said, polyamorous. I had previously had some vague awareness that there had been a free love movement in the sixties that encouraged "alternative lifestyles", but that awareness was not a sufficient motivation for me to challenge my default belief that romantic relationships could only be conducted one at a time. Acknowledging default settings is not easy.
The chance to date a pretty girl, though, can be sufficient motivation for a great many things (as is also the case with pretty boys). It was certainly a good enough reason to ask myself, "Self, what's so great about this monogamy thing?"
I couldn't come up with any particularly compelling answers, so I called Emma up and we planned a second date.
Since that fateful day, I've been involved in both polyamorous and monogamous relationships, and I've become quite confident that I am happier, more fulfilled, and a better romantic partner when I am polyamorous. This holds even when I'm dating only one person; polyamorous relationships have a kind of freedom to them that is impossible to obtain any other way, as well as a set of similarly unique responsibilities.
In this discussion I am targeting monogamy because its discovery has had an effect on my life that is orders of magnitude greater than that of any other previously-unknown known. Others I've spoken with have had similar experiences. If you haven't had it before, you now have the same opportunity that I lucked into several years ago, if you choose to exploit it.
This, then, is your exercise: spend five minutes thinking about why your choice of monogamy is preferable to all of the other inhabitants of relationship-style-space, for you. Other options that have been explored and documented include:
These types of polyamory cover many of the available options, but there are others; some are as yet unknown. Some relationship styles are better than others, subject to your ethics, history, and personality. I suspect that monogamy is genuinely the best option for many people, perhaps even most. But it's impossible for you to know that until you know that you have a choice.
If you have a particularly compelling argument for or against a particular relationship style, please share it. But if romantic jealousy is your deciding factor in favor of monogamy, you may want to hold off on forming a belief that will be hard to change; my next post will be about techniques for managing and reducing romantic jealousy.