Source: http://win.wizkids.com/bb/viewtopic....1ccb7190b8629a

I Can Adapt So Much Faster Than You: Whenever another character uses an effect that allows it choose one or more standard powers to use, after resolutions deal that character one unavoidable damage.

WK: In order for Darwin's effect to trigger, a character must use an effect that allows it to choose from a number of effects with one of those effects being or including a standard power. Note that Darwin's effect will trigger even if the chosen effect was not a standard power.

(for example, an effect states: "FREE: Choose one: Flight ability -or- Charge. This character can use the chosen effect until your next turn". If the character activated this action and chose the Flight ability, the character still used an effect that allowed it to choose a standard power, so it will trigger Darwin's effect)

Also note that the character must actually use the effect in order for Darwin's effect to trigger. If the effect is triggered and is optional and the character chooses nothing, then Darwin's effect will not trigger.

(for example, an effect states: "At the beginning of your turn, you may choose either Outwit or Perplex. This character can use the chosen power until your next turn". If the character chooses not to resolve the effect and does not choose either power, then Darwin's effect will not trigger)