From Anthony New
James Lovelock asks the question: “How can evolution by natural selection
lead to a planet with a self-regulating environment?”
(Letters, 11 July, p 57).
As an electronics engineer I can answer that question easily: any complex system
with many feedback loops will display rapid transitions between unstable states,
and frequent but small noise-induced perturbations in stable states.
An observer is therefore very likely to see an apparently self-regulating
system at any given instant, but may see sudden transitions to other stable or
metastable states if he waits long enough (or looks back far enough). External
influences (for example the Sun) can induce decaying perturbations or trigger
sharp transitions, depending on their magnitude, timing and nature.
No external control or preprogrammed thermostat is needed—it is simply
an inevitable effect of a complex feedback system. Whether you call this Gaia or
not, it appears to be how our world behaves.
Clifton, Bristol
