【英语时差8,16】史前的牙签
时间：2015-12-03 05:06:33
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（单词翻译）
If asked to imagine the first prehistoric1 tools, crafted and used by our early, hominid ancestors, you'd probably think of crude knives or spear heads, chipped from stone. You probably aren't aware of another human innovation that might be just as old. Today we'll learn about the two million year history of the toothpick, possibly one of humanity's oldest tools.
Early stone tools, like knives and scrapers, are easy for anthropologists to learn about because these items are still around. Even after two million years, a chipped stone tool is still going to be there when you dig it up. Toothpicks, however, are another story. Made from splinters of wood, thorns, or bone fragments, these can rot and
crumble3 away over time, leaving no recognizable trace. If this is so, how can an
anthropologist2 look at a two million year old fossil site and claim that these early pre-humans picked their teeth?
It's certain that no toothpick will ever last two million years, but this isn't the case with teeth. In fact, fossil teeth are the most
durable4 remnants that anthropologists work with, and some of these ancient teeth display a curious set of
grooves5. Although these might have been caused by tooth decay, a close examination of the marks seems to indicate that the grooves were worn by repeated toothpicking--probably to
alleviate6 the pain of gum disease. Indeed, these fossil grooves match the toothpick grooves in the teeth of several modern
aboriginal7 populations.
It's enough to warm every dentist's heart: The first tools weren't just for preparing food, hunting, or fighting. They might have been used for dental
hygiene8 as well.
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