Social animals need more sleep

All animals sleep.

In fact nearly all organisms experience a "circadian rhythm" dictated by the 24-hour cycle of night and day.

But interestingly, creatures that live in large social groups - for example, humans, dogs and baboons - seem to need more sleep than most.

The theory goes that we need to take time out from the tribe as a form of social isolation in order for our brains to carry out the vital unconscious task of working out our place in the social pecking order.

So while we just go gooey over a pile of sleeping puppies, it might well be that they're busy working out who's going to be at the front of the queue at milk-bar opening time.