William L Hunt  wrote or quoted:

>   A odd consequence of this method of tabulating fitness by counting
> offspring is that there is some point in the future where everyone
> alive today will be in one of two sets. One is the set that has no
> descendents at this future point in time. The other is the set where
> everyone alive at this future point in time is your descendent.

Yes:

``If your time machine has taken you sufficiently far back, you can
  divide the individuals you meet into those who are ancestors of every 
  human alive in 1995, and those who are ancestors of nobody in 1995.
  There are no intermediates.  Every individual you set eyes on when
  you step outside your time machine is either a universal human 
  ancestor or not an ancestor of anybody at all.''

 - R.D., R.O.O.E. p.37

> Estimates are that about 80% of us will be universal ancestors.

I believe that estimate is derived from a model which assumes random 
mating.

Unfortunately random mating is not a very realistic assumption. 

In particular, it is wrong for most species - since the chance of
individual males reproducing is often rather low - and a low chance
of male reproduction seriously adversely affects the probability
of being an ancestor.

I generally prefer the Dawkins take on this issue:

``"Of all organisms born, the majority die before they come
  of age. Of the minority that survive and breed, an even smaller
  minority will have a descendant alive a thousand generations
  hence. This tiny minority of a minority, this progenitorial elite,
  is all that future generations will be able to call ancestral.
  Ancestors are rare, descendants are common.''

 - R.D., R.O.O.E. p.1

....or perhaps the perspective of Gould - who observed that most
individuals from the Cambrian era have no surviving descendants
in modern times at all.

My estimate would be that /most/ of the bodies we observe will
have no distant descendants.
-- 
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 |im |yler  http://timtyler.org/  tim{at}tt1lock.org  Remove lock to reply.
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