两次喷发之间可能过去了数百万年。

Millions of years may pass between eruptions.

youdao

它发生在数百万年之后。

It happens millions of years later.

youdao

这就造成了一个难题：数百万年前消失的特征是如何突然重现的？

And this poses a puzzle: how can characteristics that disappeared millions of years ago suddenly reappear?

youdao

It's happened over the course of millions of years of human evolution, but it's happened also in a relatively recent time frame when we think about the American diet and what people are eating, but also the world diet of course.

它们发生在人类数百万年的演化历程中,在近现代,当我们考虑美国人的食谱,当然也包括全世界的食谱,同样在发生着这些变革

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选