Chance and Necessity
Natural selection accounts for the "design" of organisms,
because adaptive variations tend to increase the probability of
survival and reproduction of their carriers at the expense of
maladaptive, or less adaptive, variations. The arguments of Aquinas
or Paley against the incredible improbability of chance accounts
of the origin of organisms are well taken as far as they go. But
neither these scholars, nor any other authors before Darwin, were
able to discern that there is a natural process (namely, natural
selection) that is not random but rather is oriented and able
to generate order or "create." The traits that organisms
acquire in their evolutionary histories are not fortuitous but
determined by their functional utility to the organisms.
Chance is, nevertheless, an integral part of the evolutionary
process. The mutations that yield the hereditary variations available
to natural selection arise at random, independently of whether
they are beneficial or harmful to their carriers. But this random
process (as well as others that come to play in the great theatre
of life) is counteracted by natural selection, which preserves
what is useful and eliminates the harmful. Without mutation, evolution
could not happen because there would be no variations that could
be differentially conveyed from one to another generation. But
without natural selection, the mutation process would yield disorganization
and extinction because most mutations are disadvantageous. Mutation
and selection have jointly driven the marvelous process that starting
from microscopic organisms has spurted orchids, birds, and humans.
The theory of evolution manifests chance and necessity jointly
intricated in the stuff of life; randomness and determinism interlocked
in a natural process that has spurted the most complex, diverse,
and beautiful entities in the universe: the organisms that populate
the earth, including humans who think and love, endowed with free
will and creative powers, and able to analyze the process of evolution
itself that brought them into existence. This is Darwin's fundamental
discovery, that there is a process that is creative though not
conscious. And this is the conceptual revolution that Darwin completed:
that everything in nature, including the origin of living organisms,
can be accounted for as the result of natural processes governed
by natural laws. This is nothing if not a fundamental vision that
has forever changed how humanity perceives itself and its place
in the universe.
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| Contributed by: Dr. Francisco Ayala
|
