Final answer:
The most specific group that includes both Old World monkeys and New World monkeys is the anthropoids.
Step-by-step explanation:
The most specific group that includes both the Old World monkeys and the New World monkeys is the anthropoids. Old World monkeys belong to the group called Catarrhini, which is part of the larger group Cercopithecoidea found in Africa and Asia. The New World monkeys belong to the Platyrrhini, found in Central and South America, which are part of the infraorder Simiiformes within the suborder Haplorrhini. Both Old World monkeys and New World monkeys have distinguishing features such as prehensile tails for New World monkeys and downward-facing nostrils for Old World monkeys. Humans, on the other hand, are classified as hominids, a group that includes the great apes: chimpanzees, gorillas, and orangutans, as well as humans.