Chris Gordon-Smith  wrote or quoted:

[One big organism?]

> Suppose for a moment that we do have such a high level entity, able to
> optimise itself by selecting lower level units that are beneficial to it.
> If its environment now changes, the fitness function that it uses to select
> the lower level units may no longer be appropriate. However, it has no way
> to change this fitness function, because it is part of its fixed phenotype;
> it cannot be evolved by the lower level units (they know nothing about the
> fitness function of the high level entity).

AFAICS, nothing need be fixed.

> I think therefore that this entity cannot survive in the long term; it 
> has no way to adapt to chagning circumstances.

It is still the product of and subject to natural selection.  If it
of a type which dies out, we can expect not to see it's like around.

As always, those organisms we do see will be the ones that persist.
That's still true - even if there's only one organism in existence -
since there will not /always/ have been one organism.  IMO, if a
single large organism arises, it is probably going to be pretty
good at persisting.

> In short, I think that the driving force of evolution has to be natural
> selection between individuals, that these individuals are the units of
> evolution, and that higher level entities formed from aggregates of such
> individuals will not survive in the long term because they have no means
> to adapt.

Ecosystems consisting of single organisms could still change 
themselves according to their cirumstances.  I see no real basis
for the argument that such entities would be unable to persist.

There are perhaps fair grounds to doubt whether any such large creatures 
will come into existence in our universe.  The only serious candadites I 
see for single, large organisms are inter-galactic empires - and they are 
too distant to see very clearly at this stage.

If the question of whether single, large organisms can persist for long 
periods is confined to life in simulated universes, it becomes a less 
interesting one.
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