exponential growth

[Andre Robatino]

John de Rivaz (John at longevb.demon.co.uk) wrote:
: I have been asked for the reference to the oft-quoted "if all those who 
: have ever died were resurrected the world's population would only 
: double."

  I once read a figure, don't remember where (Harper's index?) which stated
that 1 out of 20 of all human beings who have ever lived are alive today.
The factor of two figure only sounds plausible to me if one assumes that the
population has always increased at today's rapid rate (meaning fewer people
early on), but in fact the doubling period has decreased greatly.