He says that by some estimates, laughter is a human ability that is about four million years old.

他说，根据估计，大笑作为人类的一种能力，已经有四百万年的历史了。

youdao

In a fit of laughter my friend recounts a story his friend witnessed in four consecutive days because he lives close to the infamous wall.

我的一个朋友住得离那堵墙很近，他在那里一连观察了四天，然后把一个趣事告诉给我。

youdao

In his theory, human laughter is produced in four successive emotional stages — letting loose, then deviating from the norm, followed by freely laughing and then having the laughter overflow.

在他的理论中，人的笑声是在下面四个相继阶段出现：——放松、然后偏离规范；接着无拘束地笑；最后让笑声洋溢。

youdao

In my hometown, the Chicago River -- you probably could not find anything alive in there -- (laughter) -- four decades ago.

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Actually, it was four. (Laughter.) Go ahead, I'm sorry.

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We were just talking -- he's another local boy from Hawaii. (Laughter.) He's four years younger than me, but apparently we've got some mutual friends.

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