Biology Reference
In-Depth Information
rules (also suggesting that genetic programs for the patterns are short).
Finally, the pigmented shell of certain species is covered (i.e., at least
partially obscured) by living tissue, making it unlikely that natural selection
is responsible for the evolution of pigmentation patterns.
The relative frequency of simple organisms, and the existence of organs
that have some reasonably simple components, may be explained by the
assumption that only simple features on which selection can act, can be
optimised, and have therefore survived. In toto, natural selection does not
lead to complexity but tends to avoid it. The fact that evolution has led to
many complex organisms, in addition to many simple ones, is a conse-
quence of the random addition of more and more ''programs'', many of
which happen to lead to complex features.
It is interesting to compare the findings of Wolfram with the con-
clusions of other authors. For example, according to Hengeveld and
Walter (
1999
, further references therein), optimisation of ecological
traits can rarely be achieved because environmental conditions are
very variable in space and time (see pp. 10-11) and Chapter
10
.
Wolfram's solution is more radical, since it suggests that optimisation
cannot occur even when environmental conditions are constant.
Kauffman (
1993
) doubted the overriding importance of natural selection
and, like Wolfram, concluded that many traits of organisms have
evolved not because of, but in spite of natural selection. He refers to
ideas of the rational morphologists Goethe, Cuvier, and St. Hilaire, who
tried to find some logic or laws that ''explained similar organisms as
variations on some simple mechanisms that generate living forms.'' In
some respects, this is surprisingly similar to NKS. Kauffman concluded
that species perform ''adaptive walks'' in ''rugged fitness landscapes'' that
lead them to local optima where they become trapped. Like Wolfram,
he concluded that global optima can seldom (if ever) be reached, species
are not optimally adapted.
Regulation and equilibrium in ecological systems: some
experiments and a critical discussion of arguments
given in favour of equilibrium
Ecologists may argue about the definition and significance of equilibrium
and regulation, but there are well documented cases for regulation of
natural populations, i.e., for apparent equilibrium conditions. Populations
can be regulated by a single predator, as shown, for example, by Silman et al.
(
2003
), who studied a dominant rainforest tree species, the palm
