Newsgroups: comp.ai.alife
Path: cantaloupe.srv.cs.cmu.edu!das-news2.harvard.edu!news2.near.net!howland.reston.ans.net!pipex!uknet!festival!toby
From: toby@castle.ed.ac.uk (R T Tyrrell)
Subject: Re: Reason for Short Life Spans?
X-Newsreader: TIN [version 1.1 PL8]
References: <shea.1229.000B39B3@marcam.com>
Message-ID: <D19oDx.H5y@festival.ed.ac.uk>
Sender: news@festival.ed.ac.uk (remote news read deamon)
Organization: Edinburgh University
Date: Fri, 23 Dec 1994 14:03:33 GMT
Lines: 29

Tim Shea (shea@marcam.com) wrote:
: In article <D17Jou.1uK@festival.ed.ac.uk> toby@castle.ed.ac.uk (R T Tyrrell) writes:

: >I don't think it's feasible to talk of individuals living forever.  There
: >must be a genetic fitness cost in 'building' an animal which can potentially
: >live forever, rather than just one which will 'get by' for fifty years or so.
: >And the extra cost of building a potentially immortal animal is not merited
: >if the animal is likely to die anyway in twenty-thirty years or so, due to
: >predation, accident, disease or whatever.

: This stikes me as a good explanation. I.e. it's more effective to put
: energy into reproduction than longevity (past a certain point). However
: I would also wonder -- in some cases at least -- whether the notion of
: "cost" is, well, relevant. E.g.: Does it "cost" more to make a bristlecone
: pine living several thousand years than something else living 40?
: Does the species "pay for" any adaptations which confer longevity? Or
: is it simply an emergent property?

An example cost is the need to invest more energy in building a stronger,
wider root system to make the tree less vulnerable to being blown over in
storms.  Another cost would be involved in drought-resistance (there must
be at least a few during several thousand years!).

Toby Tyrrell
Plymouth Marine Laboratory,
Prospect Place,
Plymouth PL1 3DU.

tt@pml.ac.uk
