Short answers, pulled from the story.
The scientific name for apes is Hominoidea, also called hominoids. The superfamily includes two living families: Hylobatidae (gibbons, or lesser apes) and Hominidae (great apes, including orangutans, gorillas, chimpanzees, and humans).
Apes lack tails due to a mutation in the TBXT gene. The caudal vertebrae are greatly reduced across all hominoids, resulting in the complete loss of the tail in every extant species.
Genetic analysis and fossil evidence indicate that hominoids diverged from Old World monkeys approximately 25 million years ago, near the Oligocene-Miocene boundary. Gibbons then split from the remaining hominoids around 18 million years ago.
Lesser apes are the gibbons of family Hylobatidae, comprising 20 species native to Asia, with lighter bodies, long arms adapted for brachiation, and smaller social groups. Great apes are the family Hominidae, which includes orangutans, gorillas, chimpanzees, and humans, and are generally larger and more cognitively complex.
Habitat loss, primarily the destruction of tropical rainforest, is the chief threat to most endangered ape species. For African great apes, Ebola virus is considered the single greatest threat and has been responsible for the death of at least one third of all gorillas and chimpanzees since 1990.
In 1758, Carl Linnaeus placed humans, apes, and monkeys together in the order Primates, grouping the genera Homo, Simia, and Lemur. He placed Homo sapiens alongside a second species, Homo troglodytes, based on second- or third-hand accounts, and named the orangutan Simia satyrus. This classification drew accusations of impiety from his own Lutheran archbishop.