Fossil and genetic evidence suggests that apes, particularly the chimpanzee, share the closest relation to humans. The easiest way to distinguish an ape from a monkey is by the tail. Apes do not have a tail, while monkeys do. Prosimians are considered the most primitive group of primates. Examples of prosimians include the indri, lemurs, tarsiers, sifakas, and lorises .
Prosimians have relatively smaller brains and rely more on the sense of smell.
Prosimians have structural differences in their skull and reproductive biology. All lemurs and lemur-like prosimians are endemic to Madagascar. Some nocturnal prosimians inhabit parts of Africa and Asia. Callitrichids share much in common with other New World monkeys. While Callitrichids share the above traits, they are also a very diverse group of primates, especially in appearance.