Overview

Old World monkeys are the diverse group of catarrhine primates placed in the family Cercopithecidae. These simian primates are part of the broader primate order and share a closer evolutionary relationship with the apes than with the New World monkeys. They are native to Africa and much of Asia and include many familiar forms such as macaques, baboons, guenons and colobines.

Key characteristics

Old World monkeys typically have non‑prehensile tails (some species have very short or no tails), downward‑facing nostrils, and a dental formula that differs from New World groups. Many species show well‑developed sitting pads (ischial callosities), complex social structures, and diets ranging from largely folivorous to omnivorous. Their molars are often bilophodont, a trait shared across the family.

Classification and representative species

The family divides into two main subfamilies: the Cercopithecinae (e.g., macaques, baboons, guenons, mandrills) and the Colobinae (leaf‑eating colobus and langurs). Representative genera and species include:

  • Macaca: rhesus macaque (Macaca mulatta), Japanese macaque (Macaca fuscata)
  • Papio: olive and hamadryas baboons
  • Mandrillus: mandrill and drill
  • Colobus and Procolobus: colobus monkeys
  • Presbytis, Trachypithecus: various langurs and snub‑nosed monkeys

Evolution, distribution and ecology

Catarrhine ancestors diverged from New World primates tens of millions of years ago, with Old World monkeys and apes separating later. Today they occupy forests, savannas and mountain zones across Africa and Asia. Ecologically they act as seed dispersers, browsers and prey species, and in some regions influence vegetation through group feeding behavior.

Conservation and human connections

Many species face habitat loss, hunting and fragmentation. Some, like the rhesus macaque and crab‑eating macaque, are important in biomedical research and synanthropic contexts, while others are locally revered or persecuted. Conservation measures vary by region and species, and awareness of their ecological roles and threats is growing among researchers and managers (further reading).

For summaries, species lists and taxonomic updates see curated checklists and regional guides: Old World monkeys, primate databases and conservation assessments (apes comparison, New World contrast).