“I’M YOUR HANDY MAN”
THE EMERGENCE OF THE GENUS HOMO AND BRAIN EXPANSION
1.9-1.5 million years ago
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| Reconstruction of a group of Homo habilis butchering an antelope at Olduvai in Tanzania with stone tools ca. 1.8 million years ago. Credit: Illustration by John Sibbick, courtesy of John Sibbick Illustration. This illustration is used with permission. All rights reserved. |
It is likely that the earliest known hominins to flake stone tools around two-and-a-half million years ago were members of the small-brained genus Australopithecus, perhaps with a brain size of 450 cc. Within a half a million years of the earliest stone tools, something fascinating happened: some hominids evolved with substantially larger brain sizes, over 600 cc. Scientists named these larger-brained forms Homo habilis (Latin for “Handy Man”, referring to their ability to make and use stone tools) and put them into our own genus. Another form, Homo rudolfensis, had perhaps an even larger brain (~775 cc) but a massive face with large teeth. These forms were probably responsible for much of Oldowan stone technology. There are a number of hypotheses trying to explain why and how brains started enlarging over the course of human evolution.
These hypotheses include:
• That larger brain sizes are correlated with larger group sizes in primates, so that early Homo populations may have lived in larger groups (perhaps advantageous in hunting and/or protection from predators) and needed larger “social” brain in everyday dealings with more individuals
• That tool-use and meat- and marrow-eating produced a higher quality diet, ultimately reducing gut size and allowing more energy to be devoted to the brain
• That the rise of symbolic communication (proto-language where objects, gestures, or sounds stand for some idea or concept)
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| Reconstruction of a male Homo habilis with stone tools in hand. Credit: Illustration by John Sibbick, courtesy of John Sibbick Illustration. This illustration is used with permission. All rights reserved. |
HOW DO WE KNOW?
Endocasts (casts of the inner cavity of the braincase) of fossil hominin skulls can give a good estimate of the size and shape of the brains of these forms.
WHY SHOULD I CARE?
Some of these larger-brained forms were your ancestors, and were probably responsible for the majority of the stone artifacts found in the Oldowan between 2.3 and 1.7 million years ago.
WEB RESOURCES
This website is about the origins of the earliest homo sapiens.
https://www.archaeologyinfo.com/homosapiens.htm
This PBS website does a thorough job of explaining human evolution.
https://www.pbs.org/wgbh/evolution/humans/humankind/o.html
This is another website about the genus Homo.
https://hoopermuseum.earthsci.carleton.ca/emily/eighth.html
This is Wikipedia’s website about the genus Homo.
https://en.wikipedia.org/wiki/Homo
