First tell me where the brain cells came from?
And, oh by the way, what went BANG! in the first place?
The Big Bang is not a biological theory.
I'll jump in here, since this is one of my favorite issues.
Same answer as where God came from . . .
I've argued this design issue extensively on another thread. The eye isn't particularly well designed. That is an opinion. Go out on a clear day, look up at the blue sky and notice all those little black things racing across the sky. Those are the red blood cells feeding the rods and cones that you see with, racing about feeding those same rods and cones. Disturbing your vision.
Because our eyes evolved from light sensitive patches under the skin, they are fed from above. As the eyes deepened for more efficiency, they kept the same configuration.
Squids, however, evolved in the cold water of oceans and their eyes are fed from beneath rather than from above, because it was more efficient to provide nutrients not being exposed to the cold water, from the beginning.
"Intelligent Design" is in the eye of the beholder.