Newsgroups: comp.ai.alife
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From: A.J.Hirst@uk.ac.open (Tony Hirst)
Subject: Re: a theoretical biology for alife...
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Message-ID: <A.J.Hirst-070495170717@uu-igor-mac.open.ac.uk>
Date: Fri, 7 Apr 1995 17:07:17 GMT
References: <A.J.Hirst-280395145129@uu-igor-mac.open.ac.uk> <3l9erl$632@gap.cco.caltech.edu>
Organization: HCRL, The Open University, UK
Followup-To: comp.ai.alife
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In article <3l9erl$632@gap.cco.caltech.edu>, brown@altair.krl.caltech.edu
(C. Titus Brown) wrote:
> I'm not a practicing theoretical biologist, but I do have an opinion on
> this as a practicing AL researcher.
> I think the flow of ideas should be two-way rather than one-way, as you
> seem to limit your question to.  

I was trying to solicit perceived opinions as to whether Alife was a field
within TB, or whether TB was the 'biological basis of Alife...
If, for example, I propose a set of alife models based on inheritance by
self-description, and ask for comments from TBers who regard TB as the
study of biological mechanisms, then they may well say it's implausible and
a waste of time; and if I present the model to an alife community strivi[ng
for biological plausibility, then they may respond similarly. But if I go
to a community studying abstract/theoretical/general living/evolutionary
systems, they'd look at the system with an open 'so what does it buy me'
attitude....

>The two interact in an interesting way;
> theoretical biology deals with high-level population models which are
> supportable through biological investigation, while AL deals with low-level
> population models which exhibit self-organization.  The distinction of low-
> level vs. high-level that I make is in the design of the system; theoretical
> biology can ignore simple interactions between members of the population,
> while Artificial Life models necessarily define these interactions in the
> hope of discovering emergent behaviors.
> 
> In other words, I consider the main focus of theoretical biology to be on
> a top-down description, while I think the main focus of Artificial Life to
> be on a bottom-up implementation.
> 
OK - but some comments:

As far as my limited knowledge goes, I thought pop level models only
comprise a part of TB; TB also considers genetic mechanisms, developmental
models etc and seems to be the proving ground for novel
extensions/critiques to the neo-darwinist tradition in evoly biol.

As to alife, agreed - ecology models do use bottom up methods to generate
pop level stats etc, but it also, eg, uses fitness functions derived from
pop level requirements and may thus be seen as using a high level
orthogenetic goal to drive evolution (NOT bioly plausible).

wrt fitness functions, I think there's scope for much confusion between
fitness as a measure of pop behaviour, fitness as a statistical predictor
of pop dynamics, fitness as a statistical prescriber of evoly direction and
fitness as an optimisation (prescribed) goal of evolution 

monty
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