VOA慢速英语 2007 0904b

VOICE ONE:

This is SCIENCE IN THE NEWS in VOA Special English. I'm Faith Lapidus.

VOICE TWO:

And I'm Steve Ember. This week, we will tell how a discovery in Kenya has started a scientific debate about early human ancestors. We also will tell how people might have influenced the diet of birds on Antarctica. And, we will answer a question from Vietnam about an eye disease.

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VOICE ONE:

 
A complete Homo erectus skull¹ and the upper jaw² of Homo habilis at a news conference at the National Museum of Kenya
A team of researchers recently announced discovery of two fossils that it says should change the theory of human development. The Koobi Fora Research Project says the fossils came from two ancestors of human beings. Their remains³ were discovered seven years ago in Kenya.  The British magazine Nature published a report on the discovery.

One fossil is an upper jawbone -- a long curved bone along the mouth. The other is a skull -- the bone that holds and helps protects the brain. The researchers say the upper jawbone is about one million four hundred forty thousand years old. They believe the skull fossil is even older.  It is believed to be about one million five hundred fifty thousand years old. 

VOICE TWO:

Anthropologists Maeve Leakey and her daughter, Louise, are leading the Koobi Fora Project. They say the jawbone belonged to the early human ancestor Homo habilis. They say it is from a period when scientists thought Homo habilis had already disappeared from Earth. 

The Leakeys say the discovery means that Homo habilis lived at the same time as Homo erectus. If confirmed, that could change scientific theories about the development of modern human beings. 

VOICE ONE:

Many scientists believe that humans, or Homo sapiens, developed from Homo erectus. They also believe that Homo erectus developed from Homo habilis.

The Leakeys say the shared period of existence makes it unlikely that Homo erectus developed from Homo habilis. They say both species probably developed two million to three million years ago. And, they say, the long period as separate species probably means they were not competing for food and shelter. They survived as species using different methods.

Other anthropologists are not persuaded that the jawbone forces a change in the theory of human development. They say it is likely that the Leakey's mistakenly identified a Homo erectus jawbone as a Homo habilis one.

VOICE TWO:

The Koobi Fora Project researchers also found a skull they identified Homo erectus. However, it is the smallest Homo erectus skull ever found. The researchers say the small skull suggests a sexual dimorphism was common among the Homo erectus species. Sexual dimorphism is when the size difference between the sexes is great. This quality would make Homo erectus closer to gorillas⁴ than human beings.

But, other scientists argue that what the researchers found is simply the skull of a very young Homo erectus, not of a small adult. They also say two fossils are not enough evidence to change a theory of development based on hundreds of finds.

There are also fossil experts who support the Leakey findings. They note that the skull found is in especially good condition making identification easier.

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VOICE ONE:

You are listening to SCIENCE IN THE NEWS in VOA Special English.  With Steve Ember. I'm Faith Lapidus in Washington.

 
Adelie penguin⁵
Two hundred years ago, Adelie penguins⁶ ate a diet rich in fish along the coast of Antarctica. But researchers say the diet of these black and white birds is very different now. They say the penguins began to depend on small sea organisms for food after fish populations decreased.

Scientists from universities in the United States and Canada announced the discovery. They reported their findings in the Proceedings⁷ of the National Academy of Sciences.

VOICE TWO:

Steven Emslie and William Patterson studied the chemistry of the eggshells of Adelie penguins. They used pieces of the shells from Ross Island in the Ross Sea.  Explorers collected the eggs there in the nineteen hundreds. The cold Antarctic climate kept them in good condition. 

The most recent eggs in the study were one hundred years old. The oldest were thirty eight thousand years old. The researchers compared the chemistry of the shells with the chemistry of fish and small sea organisms like krill. 

VOICE ONE:

One finding was surprising. Climate change about ten thousand years ago did not make major changes in what the animals ate, the researchers say. But they found that the chemistry of the eggshells became very different during the past two centuries. The chemistry changed from heavier to lighter⁸ isotopes⁹ of carbon and nitrogen. Isotopes are a form of chemical element.

The researchers believe that people were important in this change. They say the populations of krill in the southern seas increased after hunters killed almost all the Antarctic fur seals in the nineteenth century. 

VOICE TWO:

In the twentieth century, hunting of whales greatly decreased the whale population. Whales and seals eat large amounts of krill. So the reduction of those animals increased the krill population. The researchers believe the penguins started eating more krill because it was easily available to them. It was also easier for the birds to gather krill than catch fish.

Today, the population of krill also is threatened by an increased number of krill fisheries. The researchers say climate warming caused by humans also is reducing the sea organisms. They say this means the choice of foods for Adelie penguins has gotten smaller.

Mister Emslie works at the University of North Carolina in Wilmington, North Carolina. Mister Patterson is at the University of Saskatchewan in Saskatoon. 

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VOICE ONE:

The retina is the sensory¹⁰ tissue in the back part of the eye. It gathers light and captures images from the lens, much like film in a camera. The retina processes these images into signals that travel through the optic nerve to the brain.

Diseases of the retina can cause vision loss over time.

A thirty-year-old listener in Vietnam says he cannot see well and doctors have told him he has retinal degeneration. This is the loss or destruction of the sensory tissue of the retina. Trinh Phuong Bac says he first developed problems in his right eye when he was a child. He would like to know more about this disease.

VOICE TWO:

Emily Chew is a deputy division director at America's National Eye Institute. She says it is true what doctors have told our listener: there is no cure for retinal degeneration.

She says most cases are considered genetic¹². Scientists have been attempting to develop gene¹¹ treatments for it.  In recent years, there have been some reports of possible progress. But Doctor Chew says these studies of experimental gene therapies have only involved animals.

VOICE ONE:

Recently, the National Eye Institute reported the findings of a study of diet and a disease called retinopathy. It says the omega-three fatty acids EPA and DHA, both found in fish, protected mice against the development and progression of retinopathy. The study showed that decreasing omega-six fatty acids in the diet also helped. The study was published recently in Nature Medicine.

The findings could be useful to research into retinopathy in humans, including a common cause of vision loss in diabetics. A separate form can lead to permanent blindness in babies born too early.

VOICE TWO:

However, Doctor Chew says this study may have no connection to treating retinal degeneration. She also says there is disagreement about whether taking high levels of vitamin A could reduce the severity of the disease. She says one study suggested that vitamin A helped some people with retinitis pigmentosa. But she notes that other investigators¹³ have disputed these findings.

Retinitis pigmentosa, or R.P, is a form of retinal degeneration. R.P. is the name for a group of diseases that can be found as early as when a person is a teenager. People with R.P. have genes¹⁴ that give incorrect orders to cells that receive light. As a result, the retina can begin to self-destruct.

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VOICE ONE:

This SCIENCE IN THE NEWS program was written by Jerilyn Watson and Caty Weaver¹⁵. Brianna Blake was our producer. I'm Faith Lapidus.

VOICE TWO:

And I'm Steve Ember. Read and listen to our programs at voaspecialenglish.com. Join us again at this time next week for more news about science in Special English on the Voice of America.

1 skull   

n.头骨；颅骨

参考例句：

• The skull bones fuse between the ages of fifteen and twenty-five.头骨在15至25岁之间长合。
• He fell out of the window and cracked his skull.他从窗子摔了出去，跌裂了颅骨。

2 jaw   

n.颚，颌，说教，流言蜚语；v.喋喋不休，教训

参考例句：

• He delivered a right hook to his opponent's jaw.他给了对方下巴一记右钩拳。
• A strong square jaw is a sign of firm character.强健的方下巴是刚毅性格的标志。

3 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

4 gorillas   

n.大猩猩( gorilla的名词复数 )；暴徒，打手

参考例句：

• the similitude between humans and gorillas 人类和大猩猩的相像
• Each family of gorillas is led by a great silverbacked patriarch. 每个大星星家族都由一个魁梧的、长着银色被毛的族长带领着。 来自《简明英汉词典》

5 penguin   

n.企鹅

参考例句：

• The penguin is a flightless bird.企鹅是一种不会飞的鸟。
• He walked with an awkward gait like a penguin.他走路的步子难看得就像企鹅。

6 penguins   

n.企鹅( penguin的名词复数 )

参考例句：

• Why can penguins live in cold environment? 为什么企鹅能生活在寒冷的环境中？ 来自《简明英汉词典》
• Whales, seals, penguins, and turtles have flippers. 鲸、海豹，企鹅和海龟均有鳍形肢。 来自《现代英汉综合大词典》

7 proceedings   

n.进程，过程，议程；诉讼(程序)；公报

参考例句：

• He was released on bail pending committal proceedings. 他交保获释正在候审。
• to initiate legal proceedings against sb 对某人提起诉讼

8 lighter   

n.打火机，点火器；驳船；v.用驳船运送；light的比较级

参考例句：

• The portrait was touched up so as to make it lighter.这张画经过润色，色调明朗了一些。
• The lighter works off the car battery.引燃器利用汽车蓄电池打火。

9 isotopes   

n.同位素；同位素( isotope的名词复数 )

参考例句：

• the many isotopes of carbon 碳的诸多同位素
• Tritium is one of the mildest radioactive isotopes. 氚是最和缓的放射性同位素之一。 来自《简明英汉词典》

10 sensory   

adj.知觉的，感觉的，知觉器官的

参考例句：

• Human powers of sensory discrimination are limited.人类感官分辨能力有限。
• The sensory system may undergo long-term adaptation in alien environments.感觉系统对陌生的环境可能经过长时期才能适应。

11 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。

12 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。

13 investigators   

n.调查者，审查者( investigator的名词复数 )

参考例句：

• This memo could be the smoking gun that investigators have been looking for. 这份备忘录可能是调查人员一直在寻找的证据。
• The team consisted of six investigators and two secretaries. 这个团队由六个调查人员和两个秘书组成。 来自《简明英汉词典》

14 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

15 weaver   

n.织布工；编织者

参考例句：

• She was a fast weaver and the cloth was very good.她织布织得很快，而且布的质量很好。
• The eager weaver did not notice my confusion.热心的纺织工人没有注意到我的狼狈相。