Sleeping alone

Came across this interesting snippet recently about babies and sleep:

"I think its quite natural for babies to want cuddles while going to sleep, and they grow out of it eventually! Don't worry what other people think, you will feel so much more empowered and less resentful if you go with what your baby is telling you. And less tired too! When I lived in China, all babies were held while they were sleeping, some of them for their entire sleeps! But they had more people in the house to hold them, whereas if you are at home alone you may like to 'do things' while baby sleeps. "
(KD)

I'm still digesting this... seems we may have things backwards here in our isolated Western family lifestyle. Why on earth, in evolutionary terms, would our babies feel comfortable sleeping in isolation from their parents? Sleep is any animal's most vulnerable state and human babies are born so very vulnerable, even when awake. Perhaps a baby who is not happy to sleep on it's own is actually really, really smart.