(Photo: 20th Century Fox)

Here's a fascinating story from the filming of the 1968 science fiction film Planet of the Apes. In that movie, there are 3 ape species: chimpanzees, gorillas and orangutans. When the actors for the ape characters put on their makeup and costumes, they segregated themselves by species:

During the filming of Planet of the Apes in 1967, Charlton Heston noted “an instinctive segregation on the set. Not only would the apes eat together, but the chimpanzees ate with the chimpanzees, the gorillas ate with the gorillas, the orangutans ate with the orangutans, and the humans would eat off by themselves. It was quite spooky.”

James Franciscus noticed the same thing filming Beneath the Planet of the Apes in 1969. “During lunch I looked up and realized, ‘My God, here is the universe,’ because at one table were all the orangutans eating, at another table were the apes, and at another table were the humans. The orangutan characters would not eat or mix with the ape characters, and the humans wouldn’t sit down and eat with any one of them.