Front view of molar shows groove from tooth picking.

Man, the Toothpick User

Early man may not have had Stim-u-dents to clean his teeth, but evidence is accruing that the use of toothpicks is as old as Homo himself. A 1.8-million-year-old molar from Kenya's Olduvai Gorge bears unmistakable evidence of having been repeatedly probed by its owner, probably with a sharp piece of wood or bone, researchers say. "We're pushing the toothpick back in time," says anthropologist Peter Ungar of the University of Arkansas, Fayetteville, who led a team that presented the dental discovery this month at a meeting of the American Association of Physical Anthropologists in San Antonio, Texas.

The tooth in question is a lower right jaw molar, labeled OH 60, found 18 years ago in Olduvai's oldest layer. It was originally identified as that of an australopithecine, but Ungar says its smaller size marks it as being from a later relative--Homo habilis or early Homo erectus. The molar has a small horizontal notch, called an interproximal groove, on the surface where it met an adjacent tooth. Microscopic examination revealed fine parallel striations in the groove. Because "no kind of mastication would produce" the marks, they had to be carved by tooth picking, says paleoanthropologist David Frayer of the University of Kansas, Lawrence. Scientists believe the scratches were made by silica in the grit adhering to the toothpick. Modern toothpicks don't leave the marks, probably because they are cleaner, scientists surmise.

Similar grooves and striations have been found in other hominids, including Neandertals. But they are missing in the more primitive Australopithecus and in higher primates such as chimpanzees. Thus, says Ungar, toothpick use, like language and war, may be another "behavior unique to our genus."