“HEY, HEY, WE’RE THE MONKEYS”
THE RISE OF MONKEYS
35 million years ago
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| Reconstruction of the early monkey, Aegyptopithecus, that emerged in the fossil record around 35 million years ago. It was found in the Fayum depression of Egypt. Credit: Illustration by John Sibbick, Courtesy of John Sibbick Illustration. This image is used with permission. All rights reserved. |
Monkeys differ from more primitive primates (called prosimians or “pre-monkeys”) by having larger brains relative to body size, a different number of teeth in the upper and lower jaws, and often a larger body size. The earliest monkey-like forms, Apidium and Aegyptopithecus emerged around 35 million years ago in the Africa. At around this time it is also believed the ancestors of the New World monkeys migrated to the Americas, possibly living on floating island of vegetation as they drifted across the Atlantic Ocean to South America, which was significantly closer to Africa than today due to plate tectonics and perhaps also a lower sea level some of the time.
In today’s world, there are many modern species of monkeys scattered over many of the world’s continents – Africa, Europe (very localized), Asia, and Central and South America – approximately 260 different species in total. There is a big division in the monkey world between what are often called “Old World monkeys,” those that live in Africa and Eurasia, and the “New World monkeys,” those living in Central and South America. This split is a very ancient one, going back probably to 35 to 40 million years ago, when it is hypothesized that the ancestors of the New World monkeys may have accidentally set forth from Africa to South America across the (then much narrower) Atlantic Ocean on a natural ‘vegetational raft’ that departed from the western shore of Africa. Upon arrival in the New World it appears they went forth and multiplied, and diversified into many species over the ensuring 30 to 40 million years. The Old World monkeys include a number of species of baboons and macaques, colobus monkeys, mandrills, vervets, guenons, and langurs, while the New World monkeys include the better-known capuchin and spider monkeys, howler monkeys, and squirrel monkeys, as well as the perhaps less well-known marmosets and tamarins, titis and sakis.
HOW DO WE KNOW?
Early monkey fossils come from well-dated geological deposits from the Fayum Depression of Egypt (then a tropical forest with a large river running through it), and show many of the characters that are seen in modern monkeys.
WHY SHOULD I CARE?
Some form of these early anthropoids (monkeys and apes) was ancestral to the human lineage. These tree-dwelling, probably nocturnal (night-feeding) primates ranged in size to that of modern squirrels to cats and probably ate a variety of plant foods and possibly small insects, lizards, and mammals.
WEB RESOURCES
This website contains discussions about primate evolution.
https://anthro.palomar.edu/primate/prim_4.htm
This is a website with a lot of information about monkeys, including monkey news.
https://www.livescience.com/monkeys/
This is another website about monkeys, including range and habitat.
https://www.sandiegozoo.org/animalbytes/t-monkey.html
This website offers a discussion of, and hypothetical scenario of, primate speciation.
https://karmatics.com/docs/evolution-still-there-are-monkeys.html
