It might be worth pointing out that some experimental animals also enter a
sort of menpause. I have found with Drosophila (Canton-S) that I can maintain
them for 60-80 days (sometimes less, sometimes more) and the females stop
producing offspring by about 40-50 days. There is a also a decline in mating
ability-old males lose their ability to make young females pregnant, because
they can't get the mating dance right. There is the occasional old male who
can suucessfully mount but is unable to dismount and dies on the females back.
Old females by contrast seem to accept the old males because they are less
choosy.
Draw your own conclusions about the application of these studies to humans.
There is also some other behavioral changes such as the loss of alarm
responsiveness and failure of "memory" which is also virtually complete by
late middle age.
It looks to me like asynchronous loss of separate organ systems, and I cannot
find any positive survival advantage for this.
Chris Driver
Deakin University
Australia
