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(as opposed to an individual-level) ontology that emerges through the interaction of
system components.
The well-known model of planetary homeostasis,
Daisyworld
, uses a simple
form of system level self-observation (Lenton and Lovelock
2001
). Planetary albedo
is affected by proportions of black and white daisies, whose relative proportions
change according to surface temperature. What is fascinating about Daisyworld is
its ability to maintain a homeostatic surface temperature while the incoming radiant
heat energy increases.
In the ecosystem artwork
Colourfield
(McCormack
2007a
), individual compo-
nents (“agents”) are bands of colour occupying a 1D lattice of cells. Genetic infor-
mation controls the colour the agent produces, along with its preference to adapt to
the colour of its neighbours and its propensity to occupy vacant neighbouring cells
(thus making a larger contribution to the overall colour distribution). A feedback
mechanism uses a colour histogram of the overall colour distribution to allocate re-
sources to each individual agent on a per-time step basis (Fig.
2.5
). Here the obser-
vation mechanism—resource allocation based on the image histogram—is implicit
and global (the system as a whole is observing itself). An individual agent's contri-
bution to the overall image influences the production of its own resources and those
of others. The more cells an individual occupies, the greater the reliance of other
individuals to it. Here feedback is an environmental reward function that favours
symbiotic adaptations because of its global nature (resources are equally divided
between cells). As the system is evolutionary, as a whole it has the ability to modify
its colour composition and distribution in response to the “self-observation” pro-
vided by this feedback mechanism.
A different self-observation mechanism is in operation in the ecosystem art-
work
Niche Constructions
(McCormack
2010
). Niche construction is the process by
which organisms, through their activities, modify their heritable environment (and
potentially the environments of others). Advocates of niche construction theory in
biology argue that it is an initiator of evolutionary change, rather than simply an evo-
lutionary outcome (Odling-Smee et al.
2003
). The complete set of conditions and
resources affecting an organism represent its
niche
, which can be conceptualised as
a hypervolume in
n
-dimensional space.
In the Niche Constructions artwork, evolutionary line drawing agents draw on an
initially blank canvas as they move around. A set of normalised scalar values forms
an agent's genome, which directs its behaviour over its lifetime. Individual alleles
control rate of drawing curvature, “irrationality” (Fig.
2.6
), fecundity and mortality.
Agents die if they intersect with any previously drawn line or run off the page.
The canvas is seeded with a small initial population of
founder agents
—initialised
with uniformly distributed random genomes and positions—that proceed to move,
draw and reproduce. There is no limit to the number of offspring an agent may
have, but in general the lifespan of agents decreases as the density of lines becomes
greater, because it is increasingly difficult to avoid intersection with existing lines.
Eventually the entire population dies out and the image is complete. This finished
drawing represents the “fossil record” of all the generations of lines that were able
to live over the lifetime of the simulation.
