Short answers, pulled from the story.
The absence of a tail is the defining feature that separates apes from all other primates. This trait emerged from a single genetic mutation in the TBXT gene that occurred millions of years ago. The mutation silenced the gene responsible for tail development, making it a shared trait that defines the entire superfamily Hominoidea.
The evolutionary split between the lesser apes and the great apes occurred approximately 18 million years ago. The lesser apes, known as gibbons, split from the rest of the hominoids around 18 million years ago, while the great apes diverged from the gibbons about 14 million years ago. This divergence marked the beginning of a long separation that resulted in the diverse array of species seen today.
The last common ancestor of humans and chimpanzees lived between 5 and 10 million years ago. The genetic evidence suggests that humans and chimpanzees share a common ancestor that lived in Africa, and that the two lineages diverged from that ancestor millions of years ago. This period has been the subject of intense scientific debate and research.
Researchers like Jane Goodall, Dian Fossey, and Birutė Galdikas made groundbreaking discoveries about the social lives of these animals. The social behavior of apes is a subject of intense study, with these scientists contributing to our understanding of how each species adapts to its environment in unique ways.
All non-human apes are currently threatened with extinction due to habitat loss, hunting, and disease. The eastern hoolock gibbon is the least threatened, but five gibbon species are critically endangered, as are all species of orangutan and gorilla. The great apes of Africa are also facing threat from the Ebola virus, which has been responsible for the death of at least one third of all gorillas and chimpanzees since 1990.