Lemurs are a group of primates that are endemic to the island of Madagascar. They are part of the suborder Strepsirrhini, which means “wet-nosed” primates. They have a moist nose, a long snout, large eyes, and a long tail. They are mostly arboreal and nocturnal, and feed on fruits, leaves, insects, and other small animals. Lemurs are very diverse, with about 100 living species ranging in size from the tiny mouse lemur to the large indri.
But which other primates are most closely related to lemurs? To answer this question, we need to look at the evolutionary history of lemurs and their relatives.
The origin of lemurs
Lemurs belong to a group of primates called prosimians, which means “before monkeys”. Prosimians are the most primitive and ancestral primates, and they include lemurs, lorises, pottos, galagos, and tarsiers. Prosimians diverged from the common ancestor of all primates about 55 million years ago.
Prosimians were once widespread across Africa, Asia, and Europe, but they were largely replaced by more advanced primates called simians, which include monkeys and apes. Simians have larger brains, better vision, and more complex social behaviors than prosimians. Simians diverged from prosimians about 40 million years ago.
However, some prosimians managed to survive in isolated regions where simians were absent or rare. One of these regions was Madagascar, an island off the coast of Africa that separated from the mainland about 88 million years ago. Madagascar was colonized by prosimians about 50 million years ago, probably by rafting across the ocean on floating vegetation. These prosimian colonizers evolved into the diverse and unique lemurs we see today.
The closest relatives of lemurs
Among the living prosimians, the closest relatives of lemurs are lorises and galagos. Lorises are small, slow-moving primates that live in Africa and Asia. They have short tails, long limbs, and a strong grip. They feed on fruits, insects, and small vertebrates. Galagos are also known as bush babies because of their baby-like cries. They are small, fast-moving primates that live in Africa. They have long tails, large ears, and powerful hind legs. They feed on insects, fruits, and gums.
Lorises and galagos belong to the same infraorder as lemurs: Lemuriformes. Lemuriformes is one of the two main groups within Strepsirrhini. The other group is Lorisiformes, which includes pottos and angwantibos. Pottos and angwantibos are also small primates that live in Africa. They have short tails, dense fur, and a flexible neck. They feed on fruits, insects, and small vertebrates.
Lemuriformes and Lorisiformes diverged from each other about 40 million years ago. Lemuriformes is further divided into two superfamilies: Lemuroidea and Lorisoidea. Lemuroidea includes all the lemurs of Madagascar and the Comoro Islands. Lorisoidea includes all the lorises and galagos of Africa and Asia.
Lemuroidea and Lorisoidea diverged from each other about 35 million years ago. Lemuroidea is further divided into five families: Cheirogaleidae (dwarf lemurs), Daubentoniidae (aye-ayes), Indriidae (indris, sifakas, avahis), Lemuridae (true lemurs), and Lepilemuridae (sportive lemurs). Lorisoidea is further divided into two families: Lorisidae (slender lorises) and Galagidae (galagos).
Based on the evolutionary relationships described above, we can conclude that lorises and galagos are the primate groups that are most closely related to lemurs. They share a common ancestor with lemurs that lived about 35 million years ago. They also share some morphological and behavioral traits with lemurs, such as having a wet nose, a long snout, large eyes, a long tail, being arboreal and nocturnal, and feeding on fruits and insects.
However, lorises and galagos are not very closely related to lemurs compared to other simian primates. For example, monkeys and apes are more closely related to each other than they are to lemurs. Monkeys and apes share a common ancestor with lemurs that lived about 40 million years ago. Monkeys and apes also have some traits that distinguish them from lemurs, such as having a dry nose, a short snout, small eyes, a short tail or no tail, being diurnal and terrestrial, and having larger brains and more complex social behaviors.
Therefore, lemurs are a very distinct and ancient group of primates that have evolved in isolation on Madagascar for millions of years. They are the only living representatives of the prosimian radiation that once dominated the primate world. They are also among the most endangered primates due to habitat loss and hunting. Lemurs are a treasure of biodiversity and a window into the past of primate evolution.