Chris Gordon-Smith  wrote or quoted:
> Tim Tyler wrote:

> > Life needs to be able to perpetuate itself.
> > 
> > Reproduction dosen't seem to be logically necessary - it would be
> > possible for a living system to consist of a single large entity
> > that grew into new environments rather than reproducting itself -
> > and most would still judge such an organism to be alive.
> > 
> > There are large plants that operate like this - vegetative growth -
> > rather than reproduction.
> > 
> > Consider, for example:
> > 
> > ``Lomatia tasmanica: the oldest clonal plant on the planet''
> > 
> > http://www.research.utas.edu.au/reports/1998/clone.htm
> > 
> > ...an article about the world's oldest known living thing.
> 
> The ability to reproduce is certainly not necessary for an organism to be
> alive.  The plant you mention is alive, as are animals above reproducing
> age.
> 
> However, reproduction does seem to be necessary for the origin and survival
> of the living world. 
> 
> i)  Lomatia tasmanica is the product of a long process of evolutionary
> selection, and reproduction seems to be necessary for evolution (selection
> has to have something to work on)

If there's only one living thing, then it can certainly evolve by 
performing experiments on itself and choosing those that turn out
favourably.  However the experiments need not have their own 
distinct "bodies" - they can be somatic parts of the single
evolving organism.

Whether this qualifies as reproduction depends on how you pick your terms 
- but certainly a process involving chopping off your least favourite 
fingers and growing new ones might not conventionally be regarded 
as reproduction - if there's only ever one animal involved.

Evolution *only* demands change.  It doesn't depend on there being 
separate bodies to choose between.  Change can still arise when a
single organism makes modifications to itself.

Regarding the idea that there are still cells reproducing in such
scenarios, that's true - but life doesn't have to be that way.  Most
machines don't have anything corresponding to cells - and the fact
that living organisms are colonies is a result of their history -
cellularity is not necessarily an essential property of all living 
organisms.
-- 
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