When talking about primates, two main groups often come to mind and are often mixed up: monkeys in Africa and lemurs in Madagascar. Although they share a common and distant ancestor, these two groups of primates exhibit evolutionary differences that distinguish them not only physically but also behaviorally and evolutionarily.
Lemurs: The Prosimians of Madagascar
- Lemurs are part of the Prosimian group, considered the most primitive primates. They form a suborder of arboreal mammals that have taken on a monkey-like appearance while retaining some traits characteristic of insectivores. Exclusive to Madagascar, lemurs are characterized by features that link them to the earliest primates that existed on Earth.
- Physical characteristics: Lemurs include about twenty species of varying sizes (from 12 to 45 cm in length for the head and body). This group includes mouse lemurs, dwarf lemurs, bamboo lemurs, sportive lemurs, the fork-marked lemur, and ring-tailed lemurs or Lemur catta. They have a longer and rather pointed snout, along with a highly developed sense of smell. Their ears are short, and their eyes, though large, are positioned on the sides of their heads, giving them a wider field of vision but less stereoscopic view. They have longer hind legs compared to their forelimbs and a tail of similar length. They also possess grooming claws on certain fingers, an ancient trait no longer present in monkeys.
- Behavior: Lemurs have varied habits, ranging from nocturnal life to diurnal activities depending on the species. Their diet is diverse, including fruits, leaves, insects, and even flowers.
- Evolution and habitat: Isolated in Madagascar, lemurs have evolved discreetly, far from more aggressive predators and competitors found on other African continents. This isolation allowed the development of a great diversity of lemurs, ranging from tiny mouse lemurs to large indris.
Monkeys: Evolved Simians
- Monkeys belong to the Simian group, which includes not only monkeys but also great apes and humans. This group of arboreal mammalian primates is characterized by a high degree of encephalization and often hairless faces. Simians are considered more evolved than Prosimians, having developed advanced adaptations for survival and reproduction.
- Physical characteristics: Monkeys live in warm regions but not on islands. Unlike lemurs, monkeys have a flatter nose with closer-set nostrils. Their eyes are forward-facing, providing stereoscopic vision essential for judging distances when moving through trees, along with facial musculature allowing very expressive mimicry. They also have flat nails on all fingers and toes, often have calluses on their buttocks, and have a relatively larger brain, offering advanced cognitive abilities. Their often very long arms facilitate climbing and brachiation. Herbivorous species have a compartmentalized stomach. There are two infraorders: Platyrrhines (New World monkeys) with wide nostrils, 36 teeth, and often a prehensile tail (such as marmosets, capuchins, and spider monkeys); and Catarrhines (Old World monkeys), with close-set nostrils, 32 teeth, and a non-prehensile or absent tail. Among the latter, the Cercopithecoids (cercopithecids and colobids, such as colobus monkeys, macaques, and baboons) differ from the Hominoids or “great apes” (hylobatids and pongids, like gibbons, orangutans, gorillas, chimpanzees, and their fossil forms), which are closer to humans.
- Behavior: Monkeys are generally more social, living in complex groups with well-defined hierarchies. Their intelligence allows them to use tools, solve problems, and develop strategies for hunting and food gathering.
- Distribution and evolution: Monkeys are found in tropical forests, savannas, and even some urban environments worldwide, from the New World (Americas) to the Old World (Africa and Asia). This wide distribution has led to a great diversity of monkeys, adapted to a variety of ecological niches.
In short, they are two worlds and two evolutions.
Lemurs and monkeys represent two distinct branches of the primate evolutionary tree. Lemurs, with their primitive traits and exclusive presence in Madagascar, give us a glimpse into the early stages of primate evolution. Monkeys, on the other hand, illustrate an evolutionary path marked by more complex adaptations and an ability to thrive in a variety of environments. By understanding these differences, we can better appreciate the richness and diversity of the primate kingdom on Earth.
