Those with the mutation produce lactase throughout their lives.

有这个突变基因人一生都可以生成出乳糖酶。

And for most of history, humans stopped producing lactase after childhood.

从人类发展上看，大多数情况下，人类过了儿童时期生成乳糖酶了。

But the older we grow, the fewer lactase enzymes our body produces.

但是，随着年龄增长，人体产生乳糖酶越少。

This adaptation has to do with a specialized enzyme: lactase.

乳糖酶。

And the lactase that so many of us don't have, is one of these.

我们很多人所缺乏乳糖酶是其中之一。

And those bacteria possess about 1000 different kinds of enzymes of their own, including lactase.

这些细菌拥有大约 1000 种自己酶，包括乳糖酶。

An enzyme specifically created by the body for this purpose and named for what it breaks down——Lactase.

一种专门由人体为此而产生酶，并以它所分质命名——乳糖酶。

That one exception is humans, but like every other mammal, will still hardwired to stop producing lactase after infancy.

人类是个例外，但像其他哺乳动一样，在婴儿期后仍停止分泌乳汁。

This so-called lactase persistence trait probably spread as Neolithic groups trekked north and west through Europe.

这种所谓乳糖酶持久性特征可能随着新石器时代群体在欧洲向北和向西跋涉而传播。

I never go anywhere without my Lactaid, fast acting lactase enzyme.

- 如果没有我 Lactaid，速效乳糖酶，我绝去任何地方。

These are maltase, sucrase, and lactase, which break down the short chains of sugars called oligosaccharides into simple sugars, called monosaccharides.

它们包括麦芽糖酶、蔗糖酶与乳糖酶；它们能将称为寡糖短链聚合糖分成简单糖类，或称单糖。

Lactose is basically milk-sugar that can only be digested with the help of a special intestinal enzyme — lactase — which many adults do not produce enough of.

乳糖基本上可以说是奶糖——只能在一种特殊肠道酶乳糖酶帮助下消化，而许多成年人无法产生足够乳糖酶。

Those of us who can't produce the enzyme lactase in our small intestine simply let milk and cheese pass through the organ untouched, leaving the digestion to these bacteria in the large intestine.

我们这些能在小肠中产生乳糖酶人只是让牛奶和奶酪原封动地通过器官，把消化留给大肠中这些细菌。

Different enzymes help to break different linkages - for example amylases break down large polysaccharides like starch into smaller units, whereas lactase, sucrase, and maltase break down lactose, sucrose, and maltose into their monosaccharides.

同消化酶能分特定糖链，比如淀粉酶可以将淀粉等多糖分为小分子糖，而乳糖酶、蔗糖酶、麦芽糖酶则分别可将乳糖、蔗糖、麦芽糖降为相应单糖。

Today nearly 90 percent of adult Britons and Scandinavians can chug all the milk they want, whereas down toward the Mediterranean, probably less than 40 percent have lactase persistence, and fewer than ten percent in Africa and Asia.

今天，近 90% 英国和斯堪纳维亚成年人可以喝他们想喝所有牛奶，而在地中海地区，可能只有到 40% 人有乳糖酶耐受性，在非洲和亚洲只有到 10%。