Speaking as a physiologist
I can say that PJM and Kaol have pretty much expressed the opinion of the modern science community - Darwin was trying to explain how natural selection allows for the most effective (animal) designs to continue breeding in an environment, thereby spreading increasing their numbers and becoming numerically dominant (numbers matter in the wild, where there are only so many resources to go round).

The opposite goes for poor designs - due to inability to sustain their "lifestyles" (which in animal terms pretty much means feeding and procreating) they die out.

Next is the idea of mutations - perhaps a more modern theory as this was after Darwin's time - which enable a species to change. Mutations happen RANDOMLY (this has been hammered into me by my teachers for some reason) in the DNA and it is purely by chance whether a particular mutation will be beneficial to an animal (meaning it eats and has more sex and therefore more babies to spread the mutation) or be bad (i.e. has a third nipple which turns off the opposite sex, therefore it can't procreate or something...).

This means that the modern theory of evolution (which is still considered "Natural Selection" and attributed to Darwin, BTW) is actually about the trial and error system that nature seems to use. This way, a particular trial/mutation can be beneficial, spread widely and therefore lead to an adaptation of a species to its current environment.

Then again, I'm hardly the authority on the theory. After all, I've lived with a few flatmates who would make for a strong case in favour of devolution.
(thecurriedavenger, Thu 17 Jul 2008, 10:34, Reply)