Alopecia is a disease that affects humans and animals, and it causes the immune system to attack hair follicles. In severe cases, alopecia sufferers can lose all of their hair. Take these chimps, for example. It's easy to feel bad for them, but let's just say that they're not defenseless. Watch what this patron at the Twycross Zoo in Atherstone, England, caught on film. Zookeepers at the facility assured visitors that these acts of aggression were part of a process called "displaying." These intense rituals are more about securing higher positions in the social hierarchy than they are about harming other chimpanzees. That being said, let this be a lesson to everyone reading — never mess with a chimp. They're huge, strong, and sometimes menacing. No matter what they suffer from, weakness is not in their nature.