Posted by J Beck on July 15, 1999 at 03:01:20:
In Reply to: evolution ? for rpcman or anyone for that matter. posted by ludwig on July 06, 1999 at 12:40:08:
I am not a biologist; I am an astronomer. However, I have taught courses which cover
the search for extra terrestrial life, so I feel qualified to give a psuedo-
layman's (not Laman's) description of evolution and natural selection.
1) Evolution is the observable fact that over time POPULATIONS of organisms change in
attributes and characteristics. An example is bacteria which become resistant
to certain anti-biotics.
This is observable. You can keep a colony of fruit flies and watch over time how
certain characteristics change. If you can keep TWO colonies of fruit flies
for a long enough time you will see that they will eventually become different. At
some point they will become so different that they cannot interbreed and produce fertile
offspring. We then say that they are two different species of fruit flies.
If you lived a l-o-n-g time and could create/destroy land bridges you could conduct the
same experiments on elephants, horses, or even humans. The population as a whole changes.
2. Natural selection is a theory. It is a proposed mechanism for inducing change in populations.
It is so 'common sense' that one would have to be very clever to be able to argue against it.
Basically, natural selection says " Those individuals who are 'more successful' will contribute
more of their genes to future generations and influence the future populaitons.
ie. The future generations will look more like the 'successful' ones of today's population.
What does 'successful' mean? It means having a lot of viable offspring. So it is a 'no duh'
situation. Basically natural selection just says "Those who die before having offspring will
not have anyone to carry one their genes - so the future generations will not reflect their
genetics." ALSO - it is a consequence that a population will change to reflect the environment
which is causing some individuals to be more successful than others.
3. Natural selection is not the only way populations change. There are many other proposed
mechanisms.
4. Once Biologists started dealing with DNA this all became a very solid science. Fossils mean
nothing compared with what genetics tells us.