Say “evolution” and some folks think of dusty archaeologists examining bone fragments.
But, while evidence of previous life forms does play a central part in our understanding of
evolution, it is not necessary to go on a dig to see it in action—you might just look inside your
mouth.
We all learn that human beings have thirty-two teeth. They are not all the same, though;
the pointy incisors in the front are easily distinguished from the flatter, double-edged bicuspids
that run along the side. Our teeth serve different functions: those incisors are great for biting
and holding on, while the bicuspids do more of a saw-motion for chewing.
Now here is something you may not know: strictly speaking, it is not true that everyone
has thirty-two teeth. Even excluding people with dental problems, some folks have only thirty,
or even twenty-eight. The ones that are missing are often the farthest back in the mouth. Where
did they go?
One likely answer is found in evolution. A long time ago—say ten thousand years—human
beings ate much more raw meat. With a rough diet, you need lots of grinding teeth to help
prepare your food for digestion. Later, with the gradual advent of cooked foods, not all those
teeth are needed anymore. If someone is born without them, he or she does not suffer any ill
consequence; a scientist would say there is no evolutionary pressure to keep those teeth.
Source: http://amos.indiana.edu/library/scripts/mouthevol.html 【題組】41. According to the passage, which of the following statements is true?
(A) Only archaeologists understand evolution.
(B) Everyone has thirty-two teeth.
(C) Ten thousand years ago, human beings ate much more raw meat than we do now.
(D) With the gradual advent of cooked foods, we need more teeth to chew them.
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