“OF THE FIRST ORDER”
THE RADIATION OF THE PRIMATES
55 million years ago
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| Darwinius masillae is a very early Adapiform primate from the Eocene epoch. The fossil specimen pictured above is the most complete fossil primate ever found that is dated to around 47 million years ago. There is an ongoing debate as to whether Darwinius is the transitional form between simian and prosimian primate lineages. It is currently classified in the family Notharctidae, in the subfamily Cercamoniinae. Credit: Image is attributed to Jens L. Franzen, Philip D. Gingerich, Jörg Habersetzer1, Jørn H. Hurum, Wighart von Koenigswald, B. Holly Smith in a Public Library of Science article/ Wikipedia. |
The 17th century Swedish naturalist Carol Linnaeus got it right – When he developed his system of biological classification now called Linnaean taxonomy, he correctly grouped humans, apes and monkeys into the order Primates (meaning “first” or “top”). Compared to other mammals, primates are characterized by having relatively large brains to body size, nails rather than claws, stereoscopic (“3-D”) vision, color vision, and an overall reduction in the snout and organs for smell. They tend to give birth to small litters and spend more time caring for their young as well. The fossil record shows that, as is the case of most mammal orders, primates evolved from a shrew-like ancestor between 65 and 55 million years ago.
The earliest recognized primate-like fossils are Purgatorius and Plesiadipis, dating to between 65 to 55 million years old, and some of the first fossils generally considered to be true primates are Smilodectes and Notharctus dating to about 55 million years ago. These early, primitive primates would be classified as prosimians or “pre-monkeys” (modern examples of prosimians include lemurs, tarsiers, and galagos or “bushbabies”). Recently, a so-called fossil primate “missing link” was announced from a quarry in Germany: a complete skeleton of an animal called Darwinius dating to 47 million years ago that might be close to a stem ancestor of all monkeys, apes, and humans.
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| This is an artist’s conception of Darwinius masillae. A study of the skeleton reveals that Darwinius was probably an arboreal qudruped. Credit: Image is attributed to Jens L. Franzen, Philip D. Gingerich, Jörg Habersetzer1, Jørn H. Hurum, Wighart von Koenigswald, B. Holly Smith in a Public Library of Science article/ Wikipedia. |
HOW DO WE KNOW?
Fossil primates from well-dated deposits show us a general pattern of evolution from simpler prosimians to monkeys and apes, and finally hominins (proto-humans and humans). Studies of DNA have shown that humans are most closely related to modern apes (like chimpanzees, bonobos, gorillas, and oranguatans), then Old World monkeys (such as baboons, colobus, and vervet monkeys) then New World Monkeys (including capuchins, howlers, and squirrel monkeys), then prosimians.
WHY SHOULD I CARE?
The radiation (spread) of primates documents the evolution of our mammalian order and the origins of the human lineage. At every phase of primate evolution, there was a population of animals that were ancestral to ourselves, and their survival skills and reproductive success were absolutely necessary for our existence today.
WEB RESOURCES
This website from the University of Wisconsin Madison has a plethora of information about primate evolution.
https://pin.primate.wisc.edu/aboutp/evol/index.html
This is a website with a lot of information about the origins of primates, also has crossword puzzles and flash cards.
https://anthro.palomar.edu/earlyprimates/early_2.htm
This is a NOVA website about tracing the human lineage to the earliest ancestors.
https://www.pbs.org/wgbh/nova/evolution/first-primates.html
This is a web site with links to specific species of primates.
https://www.theprimata.com/factsheets.html
