Turtles have far better color vision than man. Why? I don't know. I can tell you how, but not why. The question of "why" begs the question of teleology, a doctrine explaining phenomena by their ends or purposes, and some evolutionists make the mistake of asking teleological questions. For their error the rest of us life scientists pay the price of having to defend the undefensible.
Until we find hard evidence of the creator and the blueprints, we will never know "why."
In the meantime, science muddles along trying to explain "how."
But, the fact that we do not understand does not mean it didn't occur.
Then they switch to the mild intellectual putdown:
That the complexity of it all overwhelms you is not evidence that there is an "intelligent" designer.
And (often) they go into the anti-religion insult: “Oh, you just explain everything away with the Magic Man in the Sky.” – although they don’t seem to realize that a spiritual (super-natural) explanation that cannot be understood by Man is exactly the same as a “natural” explanation that cannot (yet) be understood by Man.
I give Rudder a lot of credit for making a calm, rational case for evolution without resorting to any sort of swipe at religion. That's unusual on these threads (I will note that VadeRetro has appeared and has made his obligatory comment about "magic").
Yup, science does muddle along trying to explain how organisms work. However, evolutionists do not. For them, imagining is enough, they don't need no stinkin facts.