Chapter
Ten
Evolution and animal minds
preserved in the struggle for life, and they will produce offspring similarly char-
acterised. This ‘principle of preservation, or the survival of the fittest’, he called
‘Natural Selection’. It leads to the improvement of each creature in relation to its
conditions of life.
In more modern language, we might put it this way. If many slightly different
creatures have to compete for food, water, or other resources, and many die, and
if the survivors pass on whatever helped them survive, then their offspring must
be better adapted to that environment than their parents were. With long repe-
tition of selection over billions of years, extraordinary adaptations can gradually
appear, including fur, legs, wings, and eyes.
Paley was especially concerned with eyes, because of their intricate and delicate
design, but the principle is just the same for eyes as for anything else. In a pop-
ulation of creatures with single photosensitive cells, those with more cells might
have an advantage; in a population with eye pits, those with deeper pits might
do better; and so on until eyes with corneas, lenses, and foveas are forced into
existence. It is now thought that eyes have evolved independently more than
forty times on planet Earth. Natural selection is not the only force in evolution,
but together with mutation, genetic drift, gene flow, sexual selection, and layers
of self-organisation from the molecular level upwards, it explains how design
appears naturally without a plan or a designer.
‘Nothing in biology makes sense except in the light of evolution’, proclaimed biolo-
gist Theodosius Dobzhansky (1973). Natural selection is ‘one of the most powerful
ideas in all science’ (Mark Ridley, 1996, p. 3), ‘the single best idea anyone has ever
had’ (Dennett, 1995b, p. 4). ‘Darwin’s Dangerous Idea’ is like a universal acid that eats
through everything in its path, revolutionising our world view as it goes (1995b, Ch.
3). This ‘dangerous idea’ has become the foundation for all the biological sciences.
The process that Darwin described as ‘descent with modification’ can be thought
of as a three-step algorithm: if you have variation, heredity, and selection, then
you must get evolution. It is ‘a scheme for creating Design out of Chaos without
the aid of Mind’ (Dennett, 1995b, p. 50; see also pp. 48–52, 61–89, 324–330, and
521). American psychologist Donald Campbell (1960) described it as ‘blind vari-
ation and selective retention’. Since clever designs thrive because their competi-
tors don’t, we could also think of it as ‘design by death’.
This scheme is an inevitable process that requires no designer and no plan. It
needs no foresight and no intentions. It need not happen for any purpose or
towards any end. It could all be done by a ‘Blind Watchmaker’ (Dawkins, 1986).
Paley’s eyes and ears, valves and mating calls were designed all right, but no
designer was required.
DIRECTED EVOLUTION
Despite Darwin’s insight, the idea that evolution still requires a guiding hand
seems endlessly appealing and has often reappeared. Jean-Baptiste Lamarck
(1744–1829) agreed with Darwin that species might gradually change into other
species, but he proposed first an individual force (an animal’s drive to adapt to its
conditions) that produced progress in one direction, and second the inheritance
of acquired characteristics (this is now referred to as Lamarckism even though
‘Nothing in biology
makes sense except in
the light of evolution’(Dobzhansky, 1973)Natural selection is ‘a
scheme for creating
Design out of Chaos
without the aid of Mind’(Dennett, 1995b, p. 50)FIGURE 10.2 • The evolutionary algorithm
(Dennett, 1995b, p. 50)If you have Variation
Selection and
Heredity
You must get EvolutionOr ‘Design out of Chaos
without the aid of Mind’