Why is polygamy illegal? Marriage used to be defined as one man plus one woman with the potential, in principle, to have kids. Then we opened it up to include two men or two women. With the miracle of science, it could even be one man who used to be a woman and one woman who self-defines as a parrot. And yet even as the biology of marriage evolves rapidly, we still keep a limit on numbers. Not so the fundamentalist Mormons in Channel 4’s Three Wives, One Husband (Thursdays, 9pm).

A few years ago, one would’ve watched this show for a laugh. Modern times dictate that we do so with an open mind. And what is so awful about Abel Morrison, his three wives and 12 children who reside in the desert of Utah? The kids live as kids should – like savages – and the adults pray together, laugh together and are remarkably frank about the flaws of their system. No one is kept against their will; the women could walk off and take the kids with them.