Effect of Polygamy?

There is a species of lizard in which the presence of harems can increase “female impersonation” genes:

In the rock-paper-scissors game, paper always covers rock, scissors always cut paper, and rock always breaks scissors, only to be covered by paper again, and so on. In the lizard version, mating is the objective: orange-throated males beat out blue-throats, blue-throats overpower yellow-striped throats throats and yellow-striped throats checkmate orange-throats. These relations have generated a six-year cycle in which the three distinct morphs take turns being predominant.

When the temperate blue-throats, which keep harems of three females and defend small territories, are the most common males, even small numbers of aggressive oranges can take over. These lizards are "ultradominant," brimming with testosterone, keeping harems of up to seven females and defending large territories. Just one generation later, oranges dominate.

But then a few yellow-stripes can easily infiltrate the orange camps, passing themselves off as females and secretly copulating. (A related strategy was featured in the movie _Shampoo_, in which Warren Beatty cuckolded husbands by pretending to be a gay hairdresser and thereby gaining easy access to their wives.)

If this applies to humans, we can expect an increase in transsexuality in Muslim cultures. In some place, it's already starting:

One early campaigner for transsexual rights is Maryam Hatoon Molkara, who was formerly a man known as Fereydoon. Before the revolution, under the shah, he had longed to become a woman but could not afford surgery. Furthermore, he wanted religious guidance. In 1978, he wrote to Ayatollah Ruhollah Khomeini, who was to become the leader of the revolution but was still in exile, explaining his situation.

The ayatollah replied that his case was different from that of a homosexual and therefore he had his blessing.

Prediction: The Halloween Parade in Mecca will look very strange a century from now.