[originaltext]Skin may seem like a superficial human attribute, but it’s the fi

游客2023-08-08  9

问题  
Skin may seem like a superficial human attribute, but it’s the first thing we notice about anyone we meet. 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. We can make a very good estimate from the fossil record that humans probably evolved naked skin around 1.5 million years ago, and meanwhile they mostly lost their coat of fur.
Today we have a few patches of hair remaining on various parts of our bodies. But compared with apes and monkeys, we have very little. Basically, we turned our skin darker to serve as a natural sun protector in the place of the hair we lost. We think we lost this hair because of the need to keep ourselves cool when we were moving around vigorously in a hot environment. 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. 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. This was really an important revolution in human history because it allowed us to continue to evolve in equatorial environments. It really made it possible for us to continue along the path toward modern humans in Africa.
For most of human history, we all had dark skin. 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. Our species originated around 200,000 years ago and underwent tremendous diversification— culturally, technologically, linguistically, artistically— for 130,000 years. After that, a few small populations left Africa to populate the rest of the world. These early ancestors of modern Eurasians dispersed into parts of the world that had more seasonal sunshine and much lower levels of sun radiation. It’s in these populations that we begin to see real changes in the genetic makeup of natural coloring.
Today, skin color is evolving in the new mixtures of people coming together and having children with new mixtures of skin color genes. 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.
Questions 22 to 25 are based on the recording you have just heard.
22. What does the speaker mainly talk about?
23. What had probably caused humans to lose most of their hair 1.5 million years ago?
24. What does the speaker say protected early humans from the sun?
25. What happened after humans migrated from Africa to other parts of the world?

选项 A、The relation between hair and skin.
B、The growing interest in skin studies.
C、The color of human skin.
D、The need of skin protection.

答案 C

解析 讲座开头提到,皮肤是人体的一个属性,讲话者一直在研究为什么人类进化成裸猿,以及为什么世界各地有这么多不同的肤色。接下来讲话者提到,由于人类缺少毛发,皮肤变成了深色,以此来作为天然的防晒屏障;在人类进化历史的大多数时间,人类的皮肤一直是深色的,但是随着人类迁徙到太阳辐射水平较低的地方,他们的皮肤颜色又发生了变化;最后讲话者提到,当今,不同肤色的人聚集在一起又进化出了新的混合肤色,由此来解释讲座开头提到的为什么世界各地有这么多不同的肤色。因此,本文大意为人类皮肤的颜色,答案为C)。
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