Trevathan is a historian. He has brown-grayish hair and blue eyes. He is one of the immune humans of the mutated version of the ALZ-113, a man-made Alzheimer's cure which killed 99% of humans 310 years ago, but made apes smarter. The ALZ-113 mutated 312 years ago, and made humans unable to speak, and primitive. Trevathan tells the King of the Coastal Ape Colony, Proximus Caesar (a bonobo) stories, mostly about the Roman Empire. Trevathan is intelligent and opportunistic.