Those with the mutation produce lactase throughout their lives.

有这个突变基因的人一生都可以生成出乳糖。

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

从人类的发展上看，大多数情况下，人类过了儿童时期不会再生成乳糖了。

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

但是，随着年龄的增长，人体产生的乳糖越少。

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

乳糖。

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

我们很多人所缺乏的乳糖是其中之一。

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

这些细菌拥有大约 1000 种自己的，包括乳糖。

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的，并以它所分解的物质命名——乳糖。

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，但像其他哺乳动物一，儿期后仍会停止分泌乳汁。

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

这种所谓的乳糖持久性特征可能随着新石器时代的群体欧洲向北和向西跋涉而传播。

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

- 如果没有我的 Lactaid，速效乳糖，我绝不会去任何地方。

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、蔗糖与乳糖；它们能将称为寡糖的短链聚合糖分解成简单糖类，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——只能一种特殊的肠道乳糖的帮助下消化，而许多成年人无法产生足够的乳糖。

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.

我们这些不能小肠中产生乳糖的人只是让牛奶和奶酪原封不动地通过器官，把消化留给大肠中的这些细菌。

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.

不同的消化能分解特定的糖链，比如淀粉可以将淀粉等多糖分解为小分子的糖，而乳糖、蔗糖、麦芽糖则分别可将乳糖、蔗糖、麦芽糖降解为相应的单糖。

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% 的英国和斯堪的纳维亚成年人可以喝他们想喝的所有牛奶，而地中海地区，可能只有不到 40% 的人有乳糖耐受性，非洲和亚洲只有不到 10%。