For previous generations, coupling was something only trains did. Then it became a word to describe the business of finding a partner. An important business for the future of the species. But today in the developed world - and even beyond - the data shows that coupling is significantly down. Increasingly, people are just not forming those relationships. There are all kinds of theories out there now about why this is happening, ranging from the intriguing to the improbable. So what do we know about this noncoupling and its implications?

Guests:

Dr Alice Evans, visiting Associate Professor at Stanford and author of the upcoming book The Great Gender Divergence

Presenter: David Aaronovitch

Image credit: Malte Mueller, Getty Images