Evolution is not about chance happenings but about natural
selection according to environmental adaptation. There can be nothing
random about a species devlopment since no matter how low the
probabilities are of given adaptation, it is the environment which
"selects' successful traits and allows them to continue into future
generations. There is variation in species characteristics but if the
conditions favour an extreme of this characteristic, the individuals at
the other end of the scale are less likely to survive.
It could be said that some parts of the natural world are far
too complicated to have developed simply by natural selection so there
*must* have been an almighty designer - a watchmaker. The human eye
could supposedly not have evolved spontaneously but as a succession of
tiny modifications it is quite plausible. Better than no eye is 1% of an
eye and 2% is better than that, so in prehistoric organisms, the ones
with just that little bit better saw more predators and escaped, and
Dawkins' biomorphing program demostrates this quite nicely. The
changes from one generation to the next are tiny but over many
generations begin to create quite distinct, different creatures.
Structures, like the environment and indeed all animals, are not
"lucky' rolls of the evolutionary dice. Animals are stable formations of
particles, and have come to fill particular evolutionary niches, which
the environment already had in place. The surroundings place
restrictions on the particular type of development open to a species,
and different organisms exploit different opportunities. This is all
unconsious, however. A moth in Victorian London does not 'try' to be
black to blend in with the walls but blacker genes tend to survive.
Evolution cannot anticipate the future. It follows whatever
adaption seems the best option at the time, without consideration of
what problems may arise, later. An all-powerful designer could avoid
such difficulties but the process of evolution is blind. The 'sliding
eye' of the fish.
In some species, a significant part of their environment may be
another species - the cheetah and the gazelle, for example. As the
adaptations of one improves, the other 'counter-adapts' so as to
reestablish the balance - a kind of weapons race. The reason that
cheetahs do not become infintely fast and gazelles not infinitely fast
and dodgy is the other constraints in the environment.
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