I remember seeing this on Oprah. Absolutely awful, imagine losing your sight.
Apparently a chimp has a thicker skull, denser bones and harder muscles than humans that they won't be as damaged from a strike and the possibility of a knockout is drastically reduced.
Here's an interesting true story.
"I once knew a man named George, and during a break from a jam session I asked "Where are you working now?" He said "At a sanctuary with the chimps and orangutans that are too old or too vicious to be at the zoo".
"Sounds interesting" I said. He then remarked on how territorial they were, and that when they brought the feed into the sanctuary the chimps would throw their feces while puffing up their chests; they were egging on a fight. This is when I had to know, "What would happen if you punched a full grown chimp?"
The only thing he said was that on his first day new trainees all had to read a newspaper article concerning a past employee who bit off more than he could chew. Apparently he was one of these ghetto types, and thought he was tough.
One day while bringing in the feeding buckets, a chimp threw his feces at him and walked right up to this poor fellow. For reasons unknown, the worker threw a hay maker at the chimp's face.
Witnesses say the chimp did not dodge, but took the punch and before the man could retract his arm the chimp was biting his face and apparently removing his genitals with his hand-like feet. Workers subdued the chimp with tranquilizer guns, but the victim did not get to use his. The man later died due to loss of blood, as the sanctuary was very far from a hospital.
DO NOT fight a chimp unless you have a very good weapon, in which case an old world samurai would be a better match for a chimp, provided he gets a good slice in before the pain begin."