Biology Reference
In-Depth Information
5.3.4
Self-organisation according to Stuart Kauffman
Stuart Kauffman is another eminent self-organisation theorist, who,
like Prigogine, advances the themes of holism. For Jacques Monod,
life appearing was an event that had virtually no chance of occur-
ring (CN pp. 131-137) and we are therefore the result of an
accident of history, strangers in the world we inhabit. Kauffman
(1993, 1995) categorically rejects this point of view, believing that
the appearance of life expresses a phenomenon of spontaneous
emergence that was inevitable. This is why in contrast, we are
At
Home in the Universe
as the title of one of his topics says. In addi-
tion, the living world exhibits an order which cannot, in his opin-
ion, be explained simply by natural selection. He asserts that the
main organising force is a spontaneous trend towards self-organisation
(HU pp. 23-30) and backs his views with work performed with
Boolean automaton networks.
A Boolean automaton is an entity (an electric lamp, an enzyme,
a gene etc.) which can be activated or repressed. A numerical vari-
able describes its state (1 or 0 respectively). In a network of a suc-
cession of Boolean automata, the state of each of them depends on
the state of the others. The Boolean networks studied by Kauffman
to support his conception of self-organisation are deterministic. The
state of each node of the network (each automaton or entity)
depends on the state of the nodes situated upstream, according to
Boolean rules using the operators AND, OR, and EXCEPT. For
example if a node
x
depends on the state of three nodes
a
,
b
,
c
,a
rule could be:
x
is active if
a
AND
b
AND
c
are active. Another rule
would be:
x
is active if one of the nodes
a
OR
b
is active, etc.
The first experiment concerns the problem of the origin of life
(HU pp. 54-66). Kauffman considers a living system as a huge
Boolean automaton network, each automaton representing a pro-
tein or a gene. If, bathing in the primitive soup where life germi-
nated, there were thousands of chemical components of the first
living network, what was the probability of it arising simply through
molecular encounters? Kauffman showed in a computer simulation
that this probability depends on the connectivity of the network,
i.e. on the average number of potential connections for each node.
