From: Mark.OLeary@newcastle.ac.uk (M.D. O'Leary)
Newsgroups: sci.bio
Subject: Re: The Evolution of Death
Date: 10 Apr 92 12:43:55 GMT
Organization: University of Newcastle upon Tyne, UK NE1 7RU

Josh wrote:                                                                
>In Dr. Lewis Thomas's book "A Long Line of Cells", he claims that at the  
>time of death, the human body may release various hormones to produce a  
>state of euphoria which many people who have had "near-death" experiences  
>claim to have experienced.
>He also states that evolutionarily, this is a perfectly natural thing to  
>expect.  As he says (and here I paraphrase) 'Organisms who have spent the  
>last few million years dieing would no doubt have evolved some sort of  
>mechanism for coping with this situation.'  In other words, they would  
>have become good at it.
>
>My question is this.
>It seems to me that this is completely counter-intuitive.                 

I quite agree. After the reproductive machinery has shut down as part of the
ageing process, the only genes that will still be subject to selection pressure
are those that effect the survival of the _offspring_ - ie behavioural aspects,
in social animals... I would say that the evolution of a complex pathway to
'deliberately' release (or even manufacture and release!) chemicals that make
the final seconds of life more pleasant is ridiculous- or indeed, 
counter-intuitive... The proposed release could how ever be a side effect of
the gneral shut-down of the mechanisms regulating the mobilisation of such
chemicals, and their leakage into unexpected areas etc...
   This does however remind me of other aspects of death and evolution...
Biological death is obvio-usly programmed in to the organism (ie genetic) and
since a long-lived adult will compete for resources with its offspring, 
lifespan is also subject to a complex selection pressure. I guess there must
be a trade off between the older member s of a community protecting and
teaching the young as a positive survival trait, and the burden to the group
of maintaining otherwise non-productive individuals on the negative side (for
social apes at least...) In non-social populations, it must be straight 
competition for resources- mates, territory, food, nest sites etc.
But then, I have heard it suggested that death is neccessary to allow 
recombination of the gene pool (ie by allowing the offspring to live): Any
population that had biological immortality would be wiped out by the first 
significant shift in the environment that required a genetically based 
adaptation.        
   Now, supposea species was subject to such intense inter-specific competition 
and predation that individuals NEVER died of 'old age'. If you took such an
organism to a more gentle environment, would it not have a VERY long life
span? Maybe immortality? (Maybe if the dinosaurs had lived and us mammals had
had a bit more intense competition over evolutionary time, we (humans) would
now be a longer-lived species....

Of course, the other question that looms large in my head is:

"What is the difference between a living cell and a cell the instant after it 
'dies'?"

I've been thinking over that one for some years... Help!

>An interesting question.
And infuriating, too.... 8)
>Joshua Doenias
>Media Group, NeXT Computer, Inc.
>(and arm-chair Darwinist/Dawkinist)


Interested to see the responses...

Mark O'Leary