I was considering it for "intelligent life whose ultimate origin is on Earth" (ILWUOIOE) not "humans" (admittedly both are somewhat undefined) . If the births of intelligent lifeforms are ordered chronologically, then with probability P you are a member of the middle P fraction of all of them. That is the so-called "doomsday argument." So for example, with 95% chance, the total number of ILWUOIOE's there will ever be, is <20 times the total number so far. I simply am pointing out, this argument does NOT imply the last one will happen before 20T after now, where T is the timespan ILWUOIOEs have existed so far (which is perhaps T=30Kyears) -- because future ILWUOIOEs might have much longer lifespans. That incorrect argument is sometimes stated as though it were the "doomsday argument." In any case the doomsday argument is a comparatively unpowerful statistical argument, in the sense the confidence approaches 100% in a rather slow manner, not in an exponential manner like you usually encounter in the sort of statistics that makes me feel a whole lot better. So caveat emptor. I hope that if/when ILWUOIOEs do not all bite the dust, you will demand your money back. -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)