Modern human beings, Homo sapiens, are the only remaining species alive today belonging to the genus Homo, which includes species related to humans dating back to 2.3 million years ago. A recently discovered family trait may connect us more closely to our extinct relatives than previously thought: our teeth.
In modern humans “wisdom teeth,” or the molars that grow furthest back in our mouths, appear late in life, serve almost no function and are often removed during surgery. On the other hand chimpanzees, our closest living relatives, grow their first molars at about three years old and find them very useful.
Chimpanzees need the extra chompers to grind their diet of raw plant matter. Humans, on the other hand, with their narrower weaker jaws have trouble fitting all their molars and don’t need the extra crushing power. All this made scientists wonder about the extinct members of our family tree: Did Homo erectus have wisdom teeth? Did they look more like the teeth of Chimpanzees or those of Homo sapiens?
Christopher Dean and Tim Cole, both from the University College of London, have been studying the roots of molars taken from Homo erectus fossils, as well as those of chimpanzees and humans. In order to be useful for chewing, molars must first grow broad deep roots. Once these roots have grown firmly into the jaws they are ready to erupt into the mouth and help grind food for better digestion. In chimpanzees, scientifically known as Pan troglodytes, molars broaden and erupt at about the same time. In Homo sapiens however, molars go through their growth spurt long before they ever erupt.
This led Dean and Cole to their most interesting finding: the molar roots of Homo sapiens and Homo erectus broadened at about the same time. The difference is that, in our ancient relatives Homo erectus, molars then erupted almost immediately into their powerful jaws, much like in Pan troglodytes.
Modern humans don’t share the urgent need of molars anymore, resulting in later eruption, usually between the ages of 12 and 25. However, the way teeth grow has not changed very much. This may mean that teeth in modern humans have evolved differently than scientists have previously thought.
Understanding the clues left in our teeth may also give us more insight into which species may be the direct predecessors of modern humans. Other species of the Homo genus includes the extinct Homo neanderthalensis, which almost certainly interbred with modern humans; Homo heidelbergensis which was probably the first human to build elaborate shelters and routinely hunt large game, and Homo floresiensis which probably never grew over three and a half feet tall. To learn more about other species of humans, visit the Smithsonian National Museum of Natural History’s family tree.
You can read this exciting new molar research in the journal PLoS One.
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