Growing up, I had never heard a person of African origin (African American or otherwise) referred to as a "monkey". To me, calling someone a monkey meant that they were fooling-around or being silly. Or, one might refer to oneself or others as a monkey because, evolutionarily speaking, we are primates.
It not only shocked me to learn that monkey is used as on offensive term for people within a certain geographical origin, but flabbergasted that those who use it think it is a negative thing. In fact, being a human being, I'm a little offended that I someone wouldn't think to call me a monkey (which I am, both in the monkeying-around sense, and the evolutionary sense!).
I understand that there is a lot of emotional baggage attached to the word, monkey, when it is used in a derogatory way. I know that I can't understand the kind of hurt and anger it must bring to someone when such a slur is flung at them. I also know that I am now self-conscious that I will accidentally offend someone when talking about evolution.