John,
You are quite correct, evolution is a complex phenomenon and its
role is still subject to much discussion and debate. Keep in mind that
nature is amoral, there are no "good" or "bad" aspects to the natural
world, it simply is. There are no real "driving forces", there do not
need to be. As Douglas Futuyma states in his excellent text Evolutionary
Biology, "Neither natural selection nor any of the other mechanisms
(ecological, genetic, geographic, etc., my addition) are providential;
natural selection, for example, is merely the superior survival or reproduction
of some genetic variants compared to others under whatever environmental
conditions happen to prevail at the moment. Thus natural selection
cannot equip a species to face novel future contingencies, and it has no
purpose or goal-not even survival of the species."
All of those factors which ultimately drive the changes in the
genome of a population can lead to evolution, since this is ultimately
what evolution is- accumulation of variation in the genome, either through
mutation, selection, drift, or other factors. If some of the the factors
which promote such variation enhance the survival of the individual
species, then that species wins. I hope this helps.
Joe
On Tue, 6 May 1997, John Cherwonogrodzky wrote:
> Dear Colleagues:
> There was a question on the net posed by a highschool student on whether
> the only driving force in evolution was survival (Darwinian causes). Chris
> Colby replied and gave an informative concise reply that there are several
> forces involved, not just evolution. Just to add my voice to Chris', I also
> believe evolution is complex, fluidic, with several forces blending into each
> other in the creation of a final product: The main ones are:
>> - Survival. As Darwin postulated, the strongest tend to survive to leave more
> offspring.
>> - Nature abhors a vacuum. If an opportunity arises (e.g. an island emerges, a
> land formation occurs) life forms arriving there will adapt and evolve to take
> advantage of the environment.
>> - Sexual attractiveness, sexual programming. The dominant bird has bright
> plummage to attract the other sex (I forget the example, but where the female
> is dominant she is bightly coloured and the male is drab) and to stake its
> territory from others. Whether its mate is acceptable (song, dances,
> nest-building, etc.) is sometimes arbitrary but the process is essential to
> determine if its all there, of the correct species, etc.
>> - Sexual competition. A giraffe has a long neck because
> the males use this and their horns to thrash their opponents. The longer the
> neck, the better it can hits its competitors. I recall reading about an
> extinct "mouse deer from hell" that had fangs, horns, etc. though it was
> vegetarian because the species was trapped on an island and fought itself
> intensely for mates.
>> - Survival of the weakest. If an animal has a genetic abnormality, i.e. it
> cannot synthesize an essential amino acid, it has less fur to keep warm,
> etc., it may seek a food source to make up for this weakness. It then moves
> into a new niche and evolves lock-step with its weaknesses.
>> - Translatase? All reactions are reversible, even irreversible reactions are
> simply A->>>>B, A <-B. Is there a process by which one normally has genetic
> material to transcribe to messenger RNA which translates to proteins which
> handles stresses in the environment. Can one reverse the process, or can
> stresses cause a weak feedback by which the genetic structure changes subtely?
>> - Chance. An asteroid hits the earth, volcanic activity increases,
> temperatures rise, methyl hydrate and carbonate release increases, etc. The
> several stresses are too much for a species, it gets wiped out and the other
> species take advantage of the slack to flourish.
>> I'm sure there are also several other processes, but again, evolution
> appears to be complex...Take care...John
>
