【英语时差8,16】智齿的演变（下）

But, if these extra teeth were such an advantage for our ancestors, then why do most people today need to have their wisdom teeth removed? Again, the answer lies in evolution. As we humans have evolved, our skulls¹ have become slightly smaller, while our brains have actually become a bit larger. To make room for these changes, our jaws² have moved lower and further back on our skulls, and in the process, our jaws have become shorter. Early humans had longer jawbones which provided enough room for all 32 teeth. Most humans today have smaller jaws that can’t accommodate the four extra teeth. When there isn’t enough room for the teeth, they become “impacted” stuck, in other words and many of us have to have them surgically³ removed.

1 skulls   

颅骨( skull的名词复数 )； 脑袋； 脑子； 脑瓜

参考例句：

• One of the women's skulls found exceeds in capacity that of the average man of today. 现已发现的女性颅骨中，其中有一个的脑容量超过了今天的普通男子。
• We could make a whole plain white with skulls in the moonlight! 我们便能令月光下的平原变白，遍布白色的骷髅！

2 jaws   

n.口部；嘴

参考例句：

• The antelope could not escape the crocodile's gaping jaws. 那只羚羊无法从鱷鱼张开的大口中逃脱。
• The scored jaws of a vise help it bite the work. 台钳上有刻痕的虎钳牙帮助它紧咬住工件。

3 surgically   

adv. 外科手术上, 外科手术一般地

参考例句：

• Unsightly moles can be removed surgically. 不雅观的痣可以手术去除。
• To bypass this impediment an almost mature egg cell is removed surgically. 为了克服这一障碍，通过手术，取出一个差不多成熟的卵细胞。