Biology Reference
In-Depth Information
genes had yet been thoroughly studied. We now know that the con-
nectivity of these networks is very high. According to Kauffman's
own results, such networks cannot follow Boolean deterministic
rules because they would be totally chaotic. Kauffman's Boolean
networks, which are based on the Monod-Jacob model of stereo-
specific regulation (see chapter 3, §3.3), do not therefore help in
explaining how actual networks of non-specific molecules function.
From a theoretical point of view, they lead to the same paradox as
Prigogine's dissipative structures. They have to include the action
of a constraint arbitrarily applied on the system, and thus contra-
dict the very idea of self-organisation.
5.3.5
Self-organisation according to Atlan
Cybernetics has also given rise to a theory of self-organisation
(Segal, 2003). Disturbances occur in any communication channel
and affect the signal being carried. These disturbances, called
“noise”, usually have a negative effect, for example, in a television
network where the image may be fuzzy or the sound of a telephone
link inaudible. Several researchers have suggested that, instead of
exerting a negative effect, noise may have a positive role in allow-
ing a perturbed system to self-organise.
Heinz von Foerster (1911-2002) suggested a principle of “order
from noise” (von Foerster, 1960). As in Turing's reaction-diffusion
system (chapter 2, §2.2.4), if noise were to affect a system suffi-
ciently and intensely, the system could depart from its state of
equilibrium and evolve towards another more complex state. To
illustrate this principle, von Foerster used the image of a formless
set of magnets. If the set is shaken about, the magnetised surfaces
of the parallelepipeds will stick to each other and the mass will be
transformed into a more complex shape (Fig. 12). In this proce-
dure, the noise (shaking the magnets) causes self-organisation of
the system.
In the wake of von Foerster, Henri Atlan has also formulated a
theory of self-organisation from noise (Atlan, 1972, 1979, 1999). He
has demonstrated that if some of the elements of a system are
