Polygamy actually had a historical point to make and was necessary. That's why ancient cultures had polygamy but not polyandry.
Seeing that polygamy is normal in a "state of nature," as you only need one dominant, powerful male to reproduce with countless women, it's strange that we would allow "gay marriage" before we allowed polygamy, unless we dig deep into the minds of the eugenicists.
Gays can't reproduce unless they have sex with a female. Gaydom only occurs as a unfortunate series of genetic defects (at birth). By the standards of evolution, according to Darwin, Gays should fail to reproduce significantly with females in order to plague the future of mankind with gaydom, thus "survival of the fittest" kicks in quite well.
So, we don't have a "gay problem" because the numbers of gays have been the same as they've always been (even if they are more open today) and they'll never increase proportionally because they won't reproduce.
In fact, gay marriage is a good way to make gays come out into the open, and only copulate with each other, further reducing the risk of them living in the closet and marrying a woman and spreading their genetic variant of gaydom.
Thus, gay marriage is actually the fastest solution to culling the gay bloodlines. Damn, those White Democrat Eugenicist baby-killers (50% black infants are aborted) are very good at committing peaceful genocides by making certain cultures, identities and races kill themselves!
Now we have solved the mystery of why gays are being allowed to marry and not polygamists!
One misconception about the human genome is the “cookie-cutter” version, the fallacy that one gene controls one aspect behavior or physical feature of the body. Unfortunately, biology is an accumulation of small changes in the genome, acting randomly, causing a vast array of effects. Most aspects that make us “us” are in fact controlled by tons of genes acting together, much more like an extremely large orchestra, where a flute player might be holding up their partner’s trombone with his feet and a saxophone musician might have his hand on the clarinet in front of him (while playing his own instrument of course). It would simply be the most impressive orchestra you’ve ever seen.
The point being is that sexuality is extremely complex and the idea of discovering a single gene that controls it is highly unlikely to happen. The reality will likely be painted in shades of gray for individuals, where-by each person experiences degrees of homosexuality.
And once all those gays become married, the government will have a nice list (registration) of most gays, then some modern Nazi will use that list and exterminate what remains of them!