The Christians warned us that this would happen if we legalized gay marriage. Now the BBC tells us that we’ve slid down another notch on the slippery slope: interspecies marriage.

A ram and a deer are set to be “married” at a zoo in south-western China on Valentine’s Day, state-run media report. Changmao the ram and Chunzi the doe’s “unconventional relationship” have made them popular with the public.

Of course, in many ways it is like a traditional marriage …