Humans are among more than 200 species of primates living on Earth today--one of the latest products of a long history of primate evolution. But over the past 65 million years, many now-extinct primate species flourished around the world. As groups adapted to different environments, they began to acquire features and abilities that persist in many of their varied descendants, including ourselves.
The evolution of the primates is written in the fossil record. Each of the five species displayed here is representative of the primates living at a particular moment over the past 56 million years. Together, these examples reveal the development of features that are characteristic of living primates--for instance, grasping hands and feet, relatively large brains and keen eyesight.
Mural of Primate Evolution
This 1993 mural by artist Jay Matternes depicts five different kinds of extinct primates, each living at a different point during the past 56 million years.
Plesiadapis (56 million years old)
Notharctus (48 million years old)
Aegyptopithecus (30 million years old)
Proconsul (18 million years old)
Sivapithecus (8 million years old)
When most dinosaurs went extinct about 65 million years ago, mammals moved into newly vacated territories and rapidly evolved into many new species--including the ancestors of today's primates. Soon, groups of small primates were flourishing in forests around the world. Known as plesiadapiforms, these proto-primates lacked many features that characterize living primates. But significantly, their teeth were much like those of lemurs, monkeys, apes and humans--an indication that they were closely related to the direct ancestors of all modern primates.
It's All Relative
Plesiadapis cookei and other plesiadapiforms didn't look like most living primates: their eyes were set in the sides of their heads, instead of in front, and most species had non-grasping hands and feet. But plesiadapiforms were, in fact, well adapted for their environments. Enlarged nasal cavities allowed them to smell what they couldn't see, and claws served them well when scaling trees.
Chew On This
Despite its curiously enlarged front teeth, Plesiadapis had teeth very much like those of living primates. Indeed, its chewing teeth are much flatter than those of most other early mammals, which suggests that Plesiadapis ate a good deal of soft fruit and vegetation and had moved away from a primary diet of insects.