Wisdom teeth, also known as third molars, are the biggest teeth at the back of our mouth. First molars grow around age six, with second molars popping up around ages 10 to 12. Third molars generally appear between ages 17 and 25. They are called wisdom teeth because they tend to develop during a time when a person is considered to be wiser and more mature. According to scientists, when humans first came into existence 2.5 million years ago, they had a full set of 32 teeth, including four wisdom teeth.
智齿，又称第三大臼齿，是位于我们口腔后方最大的牙齿。第一大臼齿约在六岁时长出，第二大臼齿则在十岁至十二岁之间出现。第三大臼齿一般在十七至二十五岁之间出现。它们之所以被称作智齿是因为它们通常在人们被认为更加明智、更加成熟的时期出现。根据科学家的说法，人类在大约两百五十万年前出现的时候，就拥有完整的三十二颗牙齿，其中包含四颗智齿。
生活必备字词：
pop up 突然出现∕冒出
tend to V 往往会……，有……的倾向
mature a. 成熟的
come into existence 开始存在，出现
existence n. 存在
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本文节录自《常春藤生活英语》杂志，完整内容请见十二月号
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