From: Robert Bradbury (bradbury@genebee.msu.su)
Date: Sat Jan 22 2000 - 05:36:16 MST
On Sat, 22 Jan 2000, Damien Broderick wrote:
> At 09:27 PM 20/01/00 PST, Phil wrote:
>
> >enough tissue samples or maybe eggs (are eggs any good in women of advanced
> >age?).
>
> Women of advanced age don't *have* any eggs (having shed them all). That's
> what menopause is all about.
>
Actually, nit-picking on the biology, they aren't strictly speaking
"shed". Only a small fraction actually get released, the rest seem
to die and get reabsorbed (probably via apoptosis). Now why this
is the case is unclear. It is probably a result of the
fact we started out being able to produce multiple offspring but
for larger mammals this was too expensive and dangerous and so
some mechanism had to be developed for pruning the number of eggs
down to just 1 per cycle. It would have been much better if the
process could have been tuned a bit better so each cycle would
mature and release only a single egg. Although, there might be
a possibility that there is some natural selection occuring and
the egg(s) that get released are the "best" of the bunch. With
the sperm it is clear that the race to the finish line tends
to eliminate the defectives from the pack.
Robert
This archive was generated by hypermail 2.1.5 : Fri Nov 01 2002 - 15:26:22 MST