These are excerpts and elaborations from my book "The Nature of Consciousness"
Complex Systems The US biologist Stuart
Kauffman views the dynamics of “complex systems” as a manifestation of the
fundamental force that counteracts the universal drift towards disorder
required by the second law of Thermodynamics. His idea is that Darwin was only half right: systems do
evolve under the pressure of natural selection, but their quest for order is helped
by a property of our universe, the property that "complex" systems
just tend to organize themselves. Darwin's story is about the power of chance:
by chance life developed and then evolved. Kauffman's story is about destiny: life is the almost inevitable result of a
process inherent in nature. Kauffman's starting point was that cells behave like mathematical networks. In the early 1960s the
French biologist Jacques Monod and others discovered gene
regulation: genes are assembled not in a long string of instructions but in
"genetic circuits". Within the cell, there are regulatory genes whose
job is to turn on or off other genes. Therefore genes are not simply
instructions to be carried out one after the other. Genes realize a complex
network of messages. A regulatory gene may trigger another regulatory gene that
may trigger another gene…etc. Each gene is typically controlled by two to ten
other genes. Turning on just one gene may trigger an avalanche of effects. The genetic program is not a
sequence of instructions but rather a regulatory network that behaves like a
self-organizing system. By using a computer
simulation of a cell-like network, Kauffman proved that, in any organism,
the number of cell types must be approximately the square root of the number of
genes. He basically started where
Langton ended. His “candidate
principle” states that organisms change their interactions in such a way to
reach the boundary between order and chaos.
For example, the Danish
physicist Per Bak ("Self-organized criticality”, 1987) studied a pile of sand,
whose collapse under the weight of a new randomly placed grain is
unpredictable. However, when it happens, the pile reorganizes itself. While it
is impossible to predict if a particular grain will cause an avalanche, the
size of these avalanches is distributed according to a "power law".
No external force is shaping the pile of sand: it is the pile of sand that organizes
itself. Further examples include any
ecosystem (in which organisms live at the border between extinction and
overpopulation), the price of a product (which is defined by supply and demand
at the border of where nobody wants to buy it and where everybody wants to buy
it). Evolution proceeds towards the
edge of chaos. Systems on the boundary between order and chaos have the
flexibility to adapt rapidly and successfully. Natural selection and
self-organization complement each other: they create complex systems poised at
the edge between order and chaos, which are fit to evolve in a complex
environment. At all levels of
organization, whether of living organisms or ecosystems, the target of
selection is a type of adaptive system at the edge between chaos and order. In 1932 the US biologist
Sewall Wright had introduced the concept of "fitness landscapes". Fitness is the replication rate of a
genotype. A fitness landscape is a distribution of fitness values over the space
of genotypes. In other words, the fitness landscape describes all possible
genotypes, their degree of similarity and their fitness values. Fitness is
related to height in the landscape. Genotypes that are very similar are close
to each other in the landscape. Evolution is the traversing
of a fitness landscape. Peaks represent optimal fitness. Populations wander
through the landscape, driven by mutation, selection and drift, in their search
for peaks. Kauffman showed that the best strategy for reaching the peaks occurs at the
phase transition between order and disorder, or, again, at the edge of chaos.
The same model applies to other biological phenomena and even nonbiological
phenomena, and may therefore represent a universal law of nature. Adaptive evolution can be
represented as a local “hill-climbing search” that converges via fitter mutants
toward some local or global optimum.
Adaptive evolution occurs on rugged (multipeaked) fitness landscapes. The very structure of these landscapes
implies that “radiation” and “stasis” are inherent features of adaptation. The
Cambrian explosion and the Permian extinction (famous paradoxes of the fossil
record) may be the natural consequences of inherent properties of rugged
landscapes. Kauffman also noted how complex
(nonlinear dynamic) systems which interact with the external world are bound to
“classify” and “know” their world through their attractors. Kauffman's view of life can be summarized as follows: autocatalytic networks (networks that feed themselves) arise
spontaneously; natural selection brings them to the edge of chaos; a genetic
regulatory mechanism accounts for metabolism and growth; attractors lay the
foundations for cognition. The main theme of Kauffman's research is the ubiquitous trend towards self-organization. This
trend causes the appearance of "emergent properties" in complex
systems. One such property is life. The requirements for order to emerge are
far easier than traditionally assumed. There is order for free. Far from equilibrium,
systems organize themselves. The way they organize themselves is such that it
creates systems at higher levels, which in turn tend to organize themselves.
Atoms organize in molecules that organize in autocatalytic sets that organize
in living organisms that organize in ecosystems. The whole universe may be
driven by a principle similar to autocatalysis. The universe may be nothing but
a hierarchy of autocatalytic sets. Of course, one possible
objection to the whole theory of “self-organizing” systems is that no system
truly “self-organizes”: they all depend on external energy. Thus one could
claim that it is the external energy that organizes them. Self-organizing
systems, strictly speaking, do not exist. Only the universe as a whole can be
said to be truly self-organizing. Chaos as the Creator Anorther corollary to this vision of multi-layered self-organization is about the role played by chaos. Gregory Bateson, Francisco Varela, Chris Langton and Stuart Kauffman assign a creative role to chaos. A living organism is a self-organizing sysetm, a system that tries to maintain order inside. Outside there is a chaotic world, and that is the reason why the self-organization is a continuous, endless process. At that same time it is that chaotic "outside" that fosters creativity, growth and evolution. Too much "chaos" might kill the living organism, but, whenever the organism if capable of responding to chaos, the result is actually an increase in complexity and "intelligence". Back to the beginning of the chapter "Self-organization and the Science of Emergence" | Back to the index of all chapters |