For we know that the whole creation groaneth and travaileth in pain together until now.
Romans 8:22
The Gene wasn't switched off along a mythical "evolutionary journey" but rather switched off in one person--obviously sometime very soon after the flood--for it would have to be mixed into the human race at a very early stage of the gene pool to become all encompassing of humans. It is PRE-PROGRAMMED DATA built in. That's why there's SWITCHES.
"Researchers have found that, much like species of fish and lizard, 
humans also have the ability to regenerate damaged sensory organs like the eye, but somewhere on our evolutionary journey, the gene was ‘switched off.’
Trauma to the eye and, more specifically retina damage, is the leading cause of blindness in humans worldwide, as the sensory organ is remarkably complex, with a vast array of light-detecting rod and cone cells feeding light data to our central neural system."
RT