It might be impolitic to tell the growing number of children being raised in single-sex households that they are missing out on essential nutrients, as the Hollywood actor did in a now-deleted tweet. Indeed, many single-parent – or grandparent, or a gay couple - households are much more loving than those of dysfunctional couples bringing up their own kid.

But to pretend that Crews is advocating something radical is to ignore the dominant social unit that has survived through different cultures and millennia of change. Two-parent, mixed-gender households were never the only way, but all other things being equal, they are still implicitly considered the best-case scenario for a child's social and psychological development.