I think that the answers to the questions posed by
The Other Dan depend on the definition of
evolution being used. If we use the standard
definition ("evolution is the change in
allele frequency in a
population in time"), the answer to his question is no, there is no alternative. However, this is not a huge problem for
biology or biologists, as this change can not only be readily observed, but has been in
every single population studied, to date. It is thus a fact, as is the existence of carbon, gravity and stars.
However, if we use a looser definition of evolution (which, IMHO, is not a good idea), and let it include the mechanisms by which life has evolved on this planet, then there are most definitely alternative hypotheses. There is fierce debate, as has been amply noded elsewhere, over the fossil record and between the gradualist and punctuated equilibrium camps. There is even vigorous debate over very recent (in geological terms) speciations, and alternative hypotheses are often as plentiful as there are researchers.
Again, as we see so often, the answer to a good question can depend entirely on the definition of the terms being used.
Gritchka has informed me that my discussing of a 'looser' definition of evolution may lead to some confusion. Let me state this clearly:
evolution != natural selection. The former is, as I wrote above, a commonly understood and readily observable
fact, while the latter is a
mechanism by which the former may occur. Natural selection is an excellent example of a
scientific theory, and does have its alternatives (such as
sexual selection,
genetic drift, etc.).
The take home message here is that, while the answer to the questions posed above does depend on the definition of the term being discussed (evolution), it is critical that the term be properly defined. Perhaps this node should be subtitled:
Are there any scientific alternatives to natural selection?