几万年前，全球人口基数很小，所以很长时间以来每一代人哺育的孩子很少。

The worldwide human population was tiny until a few thousand years ago, and people have few children with long periods between each generation.

youdao

直到几千年前，全世界的人口还是微不足道，而且在每一代人之间，人们要长时间才有几个孩子。

Because evolution is a Numbers game.The worldwide human population was tiny until a few thousand years ago, and people have few children with long periods between each generation.

youdao

在重写产品代码的时候，我们用了同样的办法：在几周的时间里，每碰到一点代码，就重写一点。

We took the same approach when converting the main code: over a number of weeks, as we touched a bit of code, we converted it.

youdao

if I say a particle's location is i times t^2 plus j times 9t^3, for every value of time, you can put the numbers in and you can find the velocity by just taking derivatives.

一个质点的位置,i ? t^2 + j ? 9t^3,在每一个时间点,你可以把数值代入,并通过求导得到速度

耶鲁公开课 - 基础物理课程节选