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Skin may seem like a superficial human attribute, but it is the first thing we notice about anyone we meet.
皮肤似乎是人类的外表属性，这是我们见到任何人所注意到的第一件事。
As a zoologist focusing on the studies of apes and monkeys, I’ve been studying why humans evolved to become the naked ape, and why skin comes in so many different shades around the world.
作为专门研究猿类和猴子的动物学家，我一直在研究人类为什么进化为裸猿，以及为何皮肤在世界范围内以多种不同的肤色出现。
We can make a very good estimate from the fossil record that humans probably evolved naked skin around a million and a half years ago.
根据化石记录，我们可以很好地作出估计，人类可能在大约一百万年前进化出裸露的皮肤。
And meanwhile, they mostly lost their coat of fur. Today, we have a few patches of hair remaining on various parts of our bodies.
同时，他们大多失去了皮毛。现在，我们身体的几个部位仍残留着毛发。
But compared with apes and monkeys, we have very little.
但是与猿和猴相比，我们保留下来的毛发很少。
Basically, we turned our skin darker to serve as a natural sun-protector in the place of the hair we lost.
基本上，我们的皮肤变暗了，从而在失去毛发的部位起到天然的防晒作用。
We think we lost this hair because of the need to keep ourselves cool, when we were moving around vigorously in a hot environment.
我们认为，当我们在炎热的环境中剧烈运动时，由于需要保持凉爽而褪去了这些毛发。
We can’t really lose heat by breathing quickly and loudly like dogs. We have to do it by sweating. So we evolved the ability to sweat plentifully, and lost most of our fur.
我们不能像狗一样通过快速、大声地呼吸来散发热量。我们需要通过出汗来实现。因此，我们进化出了大量出汗的能力，并且失去了大部分的毛发。
Most animals protect themselves from the sun with fur. What we did in our ancestry was to produce more permanent natural coloring in our skin cells.
大多数动物都用皮毛保护自己免受阳光的晒伤。我们在远古时代所做的是在我们的皮肤细胞中产生更永久的自然色素。
This was really an important revolution in human history, because it allowed us to continue to evolve in equatorial environments.
这确实是人类历史上的一次重要革命，因为这使我们能够在赤道环境中继续进化。
It really made it possible for us to continue along the path toward modern humans in Africa.
确实，这使我们能够继续朝着非洲现代人类进化。
For most of the human history, we all had dark skin.
在人类的大部分历史中，所有人的皮肤都是深色的。
What we see today is the product of evolutionary events, resulting from the dispersal of a few human populations out of Africa around 60,000 to 70,000 years ago.
我们今天看到的是进化事件的产物，这是大约6万至7万年前一些人散布到非洲之外的结果。
Our species originated around 200,000 years ago, and underwent tremendous diversification, culturally, technologically, linguistically, artistically, for 130,000 years.
人类物种起源于大约20万年前，并且在13万年的时间里，在文化、技术、语言、艺术上都经历了巨大的多样化。
After that, a few small populations left Africa to populate the rest of the world.
之后，少数人离开了非洲，遍布世界其他地区。
These early ancestors of modern Eurasians disperse into parts of the world that had more seasonal sunshine and much lower levels of sun radiation.
这些近代欧亚人的早期祖先散布到世界各地，这些地区的季节性阳光更多，太阳辐射水平低得多。
It’s in these populations that we begin to see real changes in the genetic makeup of natural coloring.
正是在这些人群中，我们开始看到天然肤色的基因构成发生了真正的变化。
Today, skin color is evolving via new mixtures of people coming together and having children with new mixtures of skin color genes.
现在，肤色通过新的人群融合而进化，不同种族的人聚集在一起，于是后代拥有新的肤色基因混合。
We can see this in almost every large city worldwide. Not only the coloring genes, but lots of other genes are getting mixed up, too.
我们在全世界几乎每个大城市都能看到这一点。不仅肤色基因，而且许多其他基因也出现混合。
22.What does the speaker mainly talk about?
22.叙述者主要谈论了什么？
23.What had probably caused humans to lose most of their hair one and a half million years ago?
23.一百五十万年前，是什么导致人类失去了大部分毛发？
24.What does the speaker say protected early humans from the sun?
24.叙述者说什么保护了早期人类免受太阳晒伤？
25.What happened after humans migrated from Africa to other parts of the world?
25.人类从非洲分散到世界其他地方后发生了什么？
