Many years ago my mother sent me a postcard, its text beginning: ‘We’re going to Bali tomorrow and it’s all absolutely ghastly.’ It would be hard to nail one of the central contradictions of human and animal life more succinctly: the visceral tug of home that coexists with the eternal lust for wandering and adventure. Both are essential survival instincts.

The greatest journey of a lifetime is neither complete nor satisfactory until you have returned home: homecoming is what gives the journey its meaning; if you don’t believe me, ask Odysseus and Leopold Bloom. And yet home is also something to leave – ‘what is a woman that you forsake her,/And the hearth-fire and the home-acre’ – if not with joy, then at least, like Dr Watson, with the thrill of adventure in your heart. 

I have long been familiar with the fact that whenever you try to draw hard and fast barriers between humans and our fellow animals you find them dissolving and melting away: we are forever identifying continuities where people once boasted about uniqueness. You can find evidence of language all over