Darwinian natural selection could very much still be valid. Slight alterations would need to be made, consider Nirn's existence has been much shorter then Earth's, but it is still very much possible to occur. Remember, Darwin never insisted or extrapolated genetic mutation as being the initiator of natural selection. Replace DNA and solar radiation with magic, and Darwinian concepts could still be very much valid.
Come to think of it. The Anuad describes an evolution from gods, unfit to survive the mortal plane in to lesser, smaller beings able to do so.
Though as an explanation why there are certain creatures in certain places it might not be suitable. You'll end up explaining how the devs created certain creatures. Which is pleasantly congruent with the creation of Nirn but also unpleasantly obscure. Though the same can be said about Darwinian selection.
edit:
That last sentences refers back to the first sentence in the paragraph, not the second.
Total: 6749 years.
Given the fragile nature of time, though, it may vary locally... See Dragon Break.
Aah. Crap. I've been citing the wrong figure by almost 800 years?
For what it's worth though 'WWYWTD' mentions that moon phases are constant during a Dragon Broke. That is how they got to the thousand and eight years.