A 18' fence
Monkeys have tails. We are most closely related to Primates: Chimps, Gorillas, Orangatans. We have DNA which is just one jot or 1% off from these three type Great Apes. Ah, but we are animals. Look this up, if you think I have it wrong. I may indeed have my ideas wrong, but it is what I have read. Check with Jane Goodall.
More highly developed pre-frontal cortex in our brains.
Monkeys evolved to dwell in trees, whereas humans evolved for living on the ground -- changed our hip configuration, gave us flatter feet (no longer needed in trees from the time of our common ancestor with other apes an eventual monkeys).
We lost the tail that was on our most recent common ancestor between hominids and the group of animals that evolved into monkeys -- most likely because of hominids being ground dwellers as opposed to needing an extra appendage to dwell in trees.
A change in the configuration of the mouth, tongue and vocal tracts that led to eventual speech in humans.
etc., etc., etc.,
Hope this helps.
fear of injury
Not much. They are better behaved than humans.
About one or two percent difference in D.N.A