I would just like a confirm on this, because this question was asked by a deck builder at my local gamestore and I couldn't really answer for sure:

Say you control an Experiment One with no counters on
Say you cast and resolve Nylea, God of the Hunt, I believe evolve will always trigger (Because Nylea enters the BF as a Creature, right?). But I had uncertainty weather during the resolution if there could be a problem if the God is a creature or not because of a possible lack of Devotion to green.

It will not trigger if your devotion to green is less than five just after Nylea enters the battlefield.

Triggered abilities check the state of the game just after the event to see whether and how they trigger (leaves-the-battlefield triggers being the big exception to this rule). Just after Nylea entered the battlefield, it's not a creature if you have less than 5 devotion to green, so evolve doesn't trigger. In other words, Nylea is never a creature on the battlefield: the moment before it resolves, it's a creature enchantment spell on the stack; the moment after, it's a non-creature enchantment on the battlefield.

If you had enough devotion for evolve to trigger, though, you would indeed check again during resolution of evolve if Nylea has power or toughness greater than Experiment One's. If Nylea isn't a creature by that point, evolve won't do anything.

Daniel Kitachewsky
L3, Paris, France
Rules NetRep