X-Message-Number: 11849
From: "Robert Moore" <>
Subject: Life expectency questions for Thomas Donaldson
Date: Sat, 29 May 1999 20:57:48 GMT

To Thomas Donaldson:

First of all, thank you for your intelligent and prolific contributions to 

Thomas, I thought I understood teh relationship between aging and evolution 
fairly well until I read your post.

You write:

>To explain that point more clearly, most animal populations die
>in nature some time before they would come close to becoming "old" in our 
>terms. Even most human beings had a similar fate until quite >recently, 
>though people in the upper classes did live longer.

Yes, because the upper classes had superior living conditions.

>This means that you become old basically because the systems needed >to 
>keep you in top shape at high ages never had any pressure to >evolve to do 
>so at high ages... you'd already died of other
>things (diseases, accidents, etc etc).

In a tribal setting, once you live long enough to reproduce, nuture your 
young, and pass on your survival skills knowledge to your descendents, there 
would be NO evolutionary pressure to support your life.  At that point you 
would only be consuming limited resources and not contributing in any way to 
the survival of your DNA.

>It also has a corollary: if we
>maintain our current lifespans, then even without any special effort
>(not that this would help us!) we would eventually evolve to live >long 
>enough so that we would not naturally become old at, say, >100,but only at 
>ages most people would have died by accident.
I don't see this.  Frogs trapped in dark caves devolve to lose their eyes.  
Evolution usually simplifies the organism when something is not needed for 
survival. Our bodies expend a lot of energy and have additional complexity 
(cell replication error correction, etc.) to keep us living beyond 
child-bearing years.

It seems to me that in modern society, with its relatively effecient systems 
to nuture children, and preserve and pass on knowledge, there is very little 
evolutionary pressure to keep us alive after we have passed child-bearing 
age.  I would expect our 'programmed' life-expectancy (independent of living 
conditions) to decrease.

>but the frequent occurrence of old age NOW is
>a sign that we're under slow evolutionary pressure to live longer).
Isn't it merely a sign of improved living conditions?

I am looking to forward to your reply, Thomas -- As usual, I am sure I will 
learn from you post.

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