Life expectancy can be misleading.
The poorest countries are still caught in a Malthusian trap, so that when modern medicine and other technology extend life, the increased population means that everyone is poorer.
So, increased life expectancy can correlate with greater poverty. See George Clark, A Farewell to Alms.
I dunno... Generally people will have fewer children if they expect all of them to survive to adulthood than if they expect most of them to die before, and fewer children per couple all other things being equal means that each of them will be better off. I think I've seen a few TED talks about that.
Once again, here's the new thread for posting quotes, with the usual rules:
Please post all quotes separately, so that they can be voted up/down separately. (If they are strongly related, reply to your own comments. If strongly ordered, then go ahead and post them together.)