SCIENCE IN THE NEWS - Is the Human Brain Still Evolving? Som

SCIENCE IN THE NEWS - Is the Human Brain Still Evolving? Some Scientists Think So
By Katherine Gypson, George Grow and Dana Demange

Broadcast: Tuesday, November 01, 2005

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VOICE ONE:

This is SCIENCE IN THE NEWS in VOA Special English. I'm Bob Doughty¹.

VOICE TWO:

And I'm Faith Lapidus. On our program this week -- new thinking about the brain ...

VOICE ONE:

Good news for coffee drinkers ...

VOICE TWO:

And the secret of water-climbing insects.

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VOICE ONE:

Two studies suggest that the human brain continues to change through the process of evolution. The findings conflict with a common belief that the brain has evolved about as much as it ever will. Scientists say modern humans developed about two hundred thousand years ago.

 
illustration of brain
Bruce Lahn of the Howard Hughes Medical Institute and the University of Chicago led the studies. The findings appeared in Science magazine.

VOICE TWO:

Scientists looked at changes in two genes³ related to the size of the brain. These two genes do not work right in people with microcephaly. Microcephaly is a rare condition in which people are born with a brain that is much smaller than normal. Some scientists believe this is what the brain of early humans might have looked like.

In the new studies, the scientists looked at different versions of the two genes. They studied genetic⁴ material from people of different ethnic⁵ groups. They found that one version of each gene² appeared again and again.

The scientists say the changes appear to have spread because they improved the brain in some way. They say the new versions are so common, they cannot be considered an accident.

VOICE ONE:

Instead, the scientists suggest there was pressure to spread through natural selection⁶. Natural selection is a process in which genetic changes that are helpful to a species⁷ survive and spread quickly.

The scientists found that the new versions of the two genes evolved much faster in apes than in mice and rats. They decided⁸ that these changes might have had an important part in human evolution. The scientists studied how often the changes appeared in the genes of many different populations.

VOICE TWO:

They found that a version of the gene called Microcephalin formed only about thirty-seven thousand years ago. This version appears today in about seventy percent of humans. The scientists say it is more common outside of southern Africa.

The second gene is called ASPM. The studies showed that a version of this gene developed just about six thousand years ago. Today it is found in about thirty percent of all people. It is more common in people from Europe and areas including North Africa, the Middle East and South Asia.

VOICE ONE:

Different populations make use of different genetic changes. Genes must react to the pressures of many environments and threats such as disease.

The scientists who did the studies now want to see if the two genes only act on brain size or also perform other duties. They point out that the genetic changes took place around the same time as important cultural changes. These include the development of things like art and religion and, more recently, civilizations.

Scientists do not know, however, if the two genes are connected to intelligence or problem-solving abilities. Such questions about the mind produce debate. Some scientists are concerned that the new findings might be used to claim that not all groups are created equal.

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VOICE TWO:

Some insects can climb what seem like walls of water without moving their legs. They might do this to leave their eggs on land or to avoid attackers. Now, researchers in the United States have found how the insects are able to use this special skill.

John Bush and David Hu are mathematicians⁹ at the Massachusetts Institute of Technology in Cambridge. Mister Bush is a professor; Mister Hu is a graduate student. For the past four years, they have been studying how small insects travel on the surface of lakes and other areas of water.

The two men used a video camera to make high-speed images of three kinds of insects. Nature magazine reported the results of their study.

VOICE ONE:

They describe how the insects are able to climb areas where the water meets land or another surface, such as a plant. Such areas are called menisci [meh-NIH-sky].

Menisci are common in the environment. They can even be found in a glass of water, where the edge of the water rises to meet the side of the glass.

Mister Hu says most people do not recognize them because menisci are only a few millimeters high. But to small insects, he says, they are like mountains.

The two men found that the insects were unable to climb menisci with their usual movements. The insects climbed halfway¹⁰ up after a running start, but then slid back down. So the insects changed their body position to create forces that helped to pull them up.

VOICE TWO:

Two kinds of water treaders have claws at the end of their legs that can pull back, or retract¹¹. This helps the insects hold onto the surface of the water and pull it up and out of shape. As a result, the insects are able to ride on small areas in the water that can support their body weight.

Professor Bush says the insects produce extremely small menisci with their front and back legs. One meniscus creates a pulling force on another. The combined effect with the meniscus of the water pulls the insect up and over the edge of the surface.

Another insect deals with the problem another way. The larva of the waterlily leaf beetle¹² forms a rounded shape with its back. This action creates menisci at each end, and produces the same effect as with the other insects.

 
The larva of a waterlily leaf beetle prepares to go onto a leaf
The two researchers also found that the insects climbed up menisci at speeds of up to thirty body lengths a second. The fastest human runners can move about five body lengths a second.

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VOICE ONE:

Scientists are finding that coffee does more than help you stay awake. Researchers in the American state of Pennsylvania say coffee has high levels of antioxidants. Antioxidants have been shown to help prevent cancer, heart disease and other conditions.

Joe Vinson is a chemistry professor at the University of Scranton. He says Americans get more antioxidants from coffee than any other food or drink. He reported the findings at a recent meeting of the American Chemical Society.

 
Cup of coffee beside whole coffee beans
The body produces chemical substances that cause oxidation. Atoms and molecules¹³ called free radicals¹⁴ are involved. Oxidation damages cells and tissues. Experts say this damage causes many of the health problems common in older people.

VOICE TWO:

Antioxidants reduce or prevent oxidation. In recent years, other studies have shown the health value of drinking red wine and tea. Both are known to be high in antioxidants.

Professor Vinson said he and his team compared the antioxidant levels of more than one hundred different foods. They examined everything from fruits and vegetables to oils and popular drinks.

Next, the team compared its findings with information from the United States Department of Agriculture. This information showed what Americans eat and drink and in what amounts. The researchers found that coffee won in both comparisons.

Americans drink large amounts of coffee. And, coffee rated among the very best in antioxidants. One kind of fruit, the date, is actually higher in antioxidants in each serving. However, in the United States, drinking coffee is more popular than eating dates.

VOICE ONE:

Professor Vinson warned that having a diet high in antioxidants is not always a good idea. This is because the body cannot always use these compounds. Scientists do not yet fully¹⁵ understand how the body takes in and uses the substances.

Also, too much caffeine may cause nervousness and other problems.

Professor Vinson said that one to two servings of coffee a day is fine. He also suggested that people eat more fruits and vegetables. They contain not only antioxidants but also high levels of substances such as minerals and fiber¹⁶.

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VOICE TWO:

SCIENCE IN THE NEWS was written by Katherine Gypson, George Grow and Dana Demange. Cynthia Kirk was our producer. I'm Faith Lapidus.

VOICE ONE:

And I'm Bob Doughty. Our programs are online at voaspecialenglish.com. To send us e-mail, write to [email protected]. Join us again next week for more news about science in Special English on the Voice of America.

1 doughty   

adj.勇猛的，坚强的

参考例句：

• Most of successful men have the characteristics of contumacy and doughty.绝大多数成功人士都有共同的特质：脾气倔强，性格刚强。
• The doughty old man battled his illness with fierce determination.坚强的老人用巨大毅力与疾病作斗争。

2 gene   

n.遗传因子，基因

参考例句：

• A single gene may have many effects.单一基因可能具有很多种效应。
• The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。

3 genes   

n.基因( gene的名词复数 )

参考例句：

• You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。 来自《简明英汉词典》
• Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪

4 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

5 ethnic   

adj.人种的，种族的，异教徒的

参考例句：

• This music would sound more ethnic if you played it in steel drums.如果你用钢鼓演奏，这首乐曲将更具民族特色。
• The plan is likely only to aggravate ethnic frictions.这一方案很有可能只会加剧种族冲突。

6 selection   

n.选择，挑选，精选品，可选择的东西

参考例句：

• We left the selection of the team to the captain.我们把挑选队员的工作交给了队长。
• The shop has a fine selection of cheeses.那家商店有各种精美乳酪可供选购。

7 species   

n.物种，种群

参考例句：

• Are we the only thinking species in the whole of creation?我们是万物中惟一有思想的物种吗？
• This species of bird now exists only in Africa.这种鸟现在只存在于非洲。

8 decided   

adj.决定了的，坚决的；明显的，明确的

参考例句：

• This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
• There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。

9 mathematicians   

数学家( mathematician的名词复数 )

参考例句：

• Do you suppose our mathematicians are unequal to that? 你以为我们的数学家做不到这一点吗？ 来自英汉文学
• Mathematicians can solve problems with two variables. 数学家们可以用两个变数来解决问题。 来自哲学部分

10 halfway   

adj.中途的，不彻底的，部分的；adv.半路地，在中途，在半途

参考例句：

• We had got only halfway when it began to get dark.走到半路，天就黑了。
• In study the worst danger is give up halfway.在学习上，最忌讳的是有始无终。

11 retract   

vt.缩回，撤回收回，取消

参考例句：

• The criminals should stop on the precipice, retract from the wrong path and not go any further.犯罪分子应当迷途知返，悬崖勒马，不要在错误的道路上继续走下去。
• I don't want to speak rashly now and later have to retract my statements.我不想现在说些轻率的话，然后又要收回自己说过的话。

12 beetle   

n.甲虫，近视眼的人

参考例句：

• A firefly is a type of beetle.萤火虫是一种甲虫。
• He saw a shiny green beetle on a leaf.我看见树叶上有一只闪闪发光的绿色甲虫。

13 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

14 radicals   

n.激进分子( radical的名词复数 )；根基；基本原理；[数学]根数

参考例句：

• Some militant leaders want to merge with white radicals. 一些好斗的领导人要和白人中的激进派联合。 来自《简明英汉词典》
• The worry is that the radicals will grow more intransigent. 现在人们担忧激进分子会变得更加不妥协。 来自辞典例句

15 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。

16 fiber   

n.纤维，纤维质

参考例句：

• The basic structural unit of yarn is the fiber.纤维是纱的基本结构单元。
• The material must be free of fiber clumps.这种材料必须无纤维块。