On Sunday, January 23, 2000 2:26 PM Robert Bradbury bradbury@genebee.msu.su
wrote:
> > > What needs to be explained, in this view, is what would cause quint-
> > > essentially successful unicellular organisms to form communities and
> > > eventually a differentiation of labor in the development of
multicellular
> > > organisms such as ourselves. Whatever the cause, the effect obviously
> > > had survival value.
I would not reduce everything to survival value here. I think some
increases in complexity are just guaranteed because of open systems (like
Earth's biosphere) just tend to get more complex over time. (See sources
cited in "Testing Evolutionary Explanations" at my site and the Bonner book
I mention below.)
> Precisely. Forming multicellular organisms changed the scale at
> which you could operate, therefore opening up new ecological niches.
> Consider the race to "get big" in trees. The higher you go, the
> more sun you get. Now, the transition to complex cells was driven
> mostly likely by the difficulty of transfering large gene complexes
> of naked DNA between bacteria. Better for one bacteria to "get big"
> and engulf another one in its entirety (leading to mitochondria
> and chloroplasts). The problem is that once you are "big" you
> have to develop better partitioning systems or active transport
> to keep the diffusion of molecules in a very large space from
> slowing down your growth rate. Even then the added complexity
> gives you headaches (bacteria replicate in an hour or less, eukaryotic
> cells take 18-24 hours).
John Tyler Bonner goes over size and complexity increases in his _The
Evolution of Complexity by Means of Natural Selection_. I don't totally
agree with his arguments -- I think he's a bit too neoDarwinian -- but one
of his cogent arguments is that a larger size generally makes one less
dependent on the local environment. E.g., smaller organisms can store less
food...:)
> I think calling all of this "cooperation" may be stretching it
> a little. We would have to nit pick on the difference between
> cooperation and symbiosis. Particularly when the symbiosis
> may be required for the survival of both "organisms", while
> cooperation perhaps is not.
This is a good point.
> Generally, I would agree that the rise of social cooperation has
> some similarities (cooperation between people changes the scale at
> which you can "operate", opening up new niches in which you can survive).
I agree. I would also point out that from a strict Darwinian perspective,
competition explains cooperation but not vice versa. I.e., one can explain
cooperation in terms of outcompeting the non-cooperating.
Daniel Ust
http://mars.superlink.net/neptune/
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