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Lets go.
For one, Prokaryotic evolution is a lot different than the evolution that drives speciation in Eukaryotes. Sure, we see prokaryotes and even some basic forms of eukarotes (yeast) evolve and change their genetic structure to better fit their environment. We can see natural selection here, and there have even been cases of observed natural selection in larger species, as exemplified on various islands that undergo catastrophic environmental change.
However, this only at best lends support to the theory. It doesnt prove that species can differentiate, and actually kinda hurts the idea. The time it would take for two species to emerge out of one common ancestor given different environments and selectors is rather large, considering the average advantageous mutation rate of DNA. In fact, for evolution to work, we would need what are called 'hopeful monsters' - one small mutation that changes the creature immensely, yet is both advantageous enough for it to succeed and breed, and that it retains enough of its original characteristics and DNA to be able to breed with its former species.
Heres the quick of it - we have lots of evidence to support evolution. We've seen and observed Natural Selection at work, and we've seen how random mutations can allow a few lucky individuals to outcompete their buddies (most evident in our new hospital bred bacterial diseases). However, we've (to my knowledge, I havent searched pubmed this month) never seen actual speciation occur. This is a vital part of the theory, and to actually confirm that this happens, you'd need 200 years and a fuckload of flies. And even then, the argument can be made that you're forcing evolution, and that life responds differently in an actual real world environment (eg, instead of dealing with shitty environmental conditions, the species may just pick up and move away).
Evolution is still just a theory. However, so is Gravity. I'd say I'm 95% sure that evolution has solely been responsible for the diversity of lifeforms we see today. The other 5% = shit we havent yet discovered, alien life seeding our planet, etc.
And no matter what, the Earth is not under 10,000 years old, nor was it created in 7 days. Not unless the laws of physics have dramatically reversed themselves before human history.
