On Mon, Oct 03, 2005 at 02:12:08PM +0200, Toralf Lund wrote: > John Forbes wrote: > > >I suspect Toralf is alluding to the fact that more than half of the > >human beings who have ever lived are still alive today. As they > >haven't yet died, we cannot be certain that they will. (This is very > >worrying.) > > Exactly ;-)
Except that it's not a fact - just a common misconception. Around half the people who have lived to age 65 or over are alive today, but that's not the same as saying half the people who ever lived are alive. 2000 years ago the world population was roughly 200 million. If we assume a flat population, and a life expectancy around the same as today (67 years), then we'd expect around six billion deaths between then and now - about what the world population is today. Obviously population has not been flat - more people have been born (and died) in the intervening years than a constant population would predict. And the figure of 67 years for life expectancy is a gross over-estimate in historical terms. Taking those corrections into acount it's apparent that not even half the people born in just the last 2000 years are alive today, let alone half the people who ever lived.
