[ClearCase_guy]

Evolution is simply the variation over time of allele frequencies in an organism population.

That's the definition.

A definition is not evidence of the event.

[bobdsmith]

but observations are

[stremba]

It's also an observation. Allele frequencies do vary over time in organism populations. Nobody disputes that. Evolution occurs. What is necessary is to show that evolution can produce new species. This has also been observed, both in the wild and in lab experiments.