原文视听

In the natural world,
自然界中
animals' adaptation to their diet is clear.
动物适应饮食习惯的进化事例很多
Herbivorous grazers,
食草动物
like gazelles, have large flat back teeth,
比如羚羊 有着大而平的臼齿
useful for grinding down plants...
用来碾碎植物
Whereas carnivores, like lions,
而食肉动物 比如狮子
evolved sharp teeth to seize their prey
进化出尖锐的牙齿 得以抓住猎物
and rip their meat apart.
撕裂它们的肉
The change in our ancestors' teeth
一个新的实验揭示了
when they started eating meat
人类祖先开始食肉后
is revealed in a new experiment.
其牙齿的变化
Professor Peter Ungar has has spent a lifetime
彼得·恩戈教授终其一生
examining the skeletons of ancient humans.
研究这些古人类的骨骼
There's one feature in particular which fascinates him.
其中有个部位特别令他痴迷
You could call him a dentist to the ancients.
简直能当古人的牙医了
This is a jaw of Australopithecus.
这是南方古猿人的一副颌骨
Its teeth are large, they're flat,
他的牙齿又大又平
the enamel's very thick on them.
上面有着极厚的釉质

重点解释

useful for grinding down plants...用来碾碎植物

grind down磨损(磨光；磨尖；碾碎)

Mills used to use heavy stones to grind down the wheat into flour; now they use more modern machinery.

磨房过去使用笨重的石磨把麦磨成面粉; 现在它们使用的是比较现代的机械。

It won't grind down any finer than this.

不能磨得比这个再细了。

like gazelles, have large flat back teeth,比如羚羊，有着大而平的臼齿

back teeth磨牙,臼齿

One of my lower back teeth is killing me.

我的一个后牙正在痛。