VOA慢速英语2009-SCIENCE IN THE NEWS - Ancient Footprints Let Exp（在线收听）

VOICE ONE:

This is SCIENCE IN THE NEWS in VOA Special English. I'm Barbara Klein.

VOICE TWO:

And I'm Bob Doughty. This week, we will tell about evidence of early human ancestors. We also will tell about the health effects of hopeful feelings. And, we will tell about disappearing bat populations in the northeastern United States.

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Christine Galvagna, part of a Rutgers team, cleans a trail of hominid footprints

An international research team has discovered markings made by the ancestors of modern human beings more than one million years ago. The discovery is exciting because it shows the shape of the feet and walking method of the human ancestors.

Rutgers University Professor Jack Harris led the researchers and students who uncovered the marks during three years of digging. They found the ancient footprints near the village of Ileret in northern Kenya. A report about their findings was published last month in Science magazine.

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Early humans made the footprints as they walked on volcanic ash and soil that turned to rock over time. The team found two sets of prints in separate levels of rock that are about one million five hundred thousand years old.

The scientists say the prints were left by one of two human ancestors: either Homo erectus or Homo ergaster. However, many experts do not recognize a difference between the two. Homo erectus is the more commonly used name.

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Surprisingly, the footprints look much like those you would find on a sandy coastline today. In their report, the team said the discovery provides the oldest evidence of a foot structure that is generally the same as a modern human's.

The prints show how the big toe of Homo erectus is close to the other toes. In earlier species, the big toe is separated widely from the other toes -- as in the foot structure of apes. No Homo erectus foot bones have ever been found. This makes the well-preserved footprints especially valuable.

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Scientists have also learned how Homo erectus walked from the prints. Researcher Matthew Bennett of Bournemouth University used laser technology to make digital images of the footprints. These images suggest that Homo erectus walked by touching the ground first with the back of the foot and pushing off with the front -- just as we do.

The researchers could even estimate the height of the ancient individuals. One was only about a meter tall. It is believed to have been a child. The others were about the average height of modern human adults.

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The findings provide more evidence that human ancestors were able to travel long distances. Homo erectus may have left Africa for other parts of the world as early as one million eight hundred years ago.

This is only the second time that early human footprints have been found. In nineteen seventy eight, British anthropologist Mary Leaky discovered the prints of a possible human ancestor at Laetoli, Tanzania. They belonged to Australopithicus afarensis, a much earlier and smaller human-like creature that walked on two feet.

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Professor Harris says his team not only found footprints, but also many animal tracks in the rock. These include markings of hoofed animals that Homo erectus may have hunted for food. Other tracks belonged to meat-eaters. Such creatures were competitors or even threats to the early humans.

The footprints found in Kenya have let scientists step back in time to find new details about our distant ancestors and their environment.

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An American study has shown that being hopeful about future events might help you stay healthy and live longer. The study found links between people's beliefs and their risks of cancer-related death, heart disease and early death.

Researchers studied one hundred thousand women during an eight-year period, beginning in nineteen ninety-four. All of the women were fifty years of age or older. The study was part of the Women's Health Initiative, a continuing study organized by the National Institutes of Health. The findings were presented earlier this month at a meeting of the American Psychosomatic Society.

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For the study, the women were asked questions that measured their beliefs or ideas about the future. The researchers attempted to identify each woman's personality eight years after gathering the information.

The study found that the hopeful individuals were fourteen percent less likely than other women to have died from any cause. The hopeful women were also thirty percent less likely to have died from heart disease after the eight years.

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Hilary Trindle was the lead writer of the report. She is an assistant professor of medicine at the University of Pittsburgh in Pennsylvania. She says the study confirms earlier research that also linked optimistic feelings to longer life. However, this study is different from earlier research on the subject.

The researchers also gathered information about people's education, financial earnings, physical activity and use of alcoholic drinks or cigarettes. Independent of those things, the findings still showed that optimists had less of a chance of dying during the eight-year period.

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Some women who answered the study's questions were found to be cynically hostile, or highly untrusting of others. These women were sixteen percent more likely to die than the others. They also were twenty-three percent more likely to die of cancer.

The study also found that women who were not optimistic were more likely to smoke, have high blood pressure or diabetes. They were also more likely not to exercise.

Professor Tindle says the study did not confirm whether optimism leads to healthier choices, or if it actually affected a person's physical health. She says the study does not prove that negative emotions or distrust lead to bad health effects, and shorter life. Yet there does appear to be a link between the two. More research is needed to discover the exact reasons for the findings.

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In recent years, biologists have observed a sharp drop in bat populations in the northeastern United States. The biologists believe the drop has resulted from a mysterious sickness called white nose syndrome.
　
A dead Indiana bat found in Rosendale, New York, earlier this year. White nose syndrome is killing more bats over a larger area of the U.S. this year.

Little is known about the sickness. It is called white nose syndrome because of a white-colored fungus found on the faces of affected bats. The fungus seems to grow in cold weather. The affected animals were first observed in two thousand seven in New York State.

Scientists believe the disease causes bats to awaken early from their hibernation or yearly rest period. The scientists say the bats then leave their resting places in search of food during the winter when the insects they eat are not available. Without a food supply, the bats starve to death.

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Wildlife officials say white nose syndrome is not a direct threat to other animals or human beings. However, the bats' continuing disappearance could have a far-reaching effect on the environment.

Bats have survived for about fifty million years. They eat large amounts of insects, up to twenty-five percent of their body weight in one night's feeding. If fewer bats are available to eat the insects, farmers will have to use more insect-killing chemical products to protect their crops. Diseases that are spread by insects could also become more common.

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Cases of white nose syndrome have been confirmed in New York, New Jersey, Connecticut, Vermont, Massachusetts and Pennsylvania. It is difficult for scientists to know the exact number of bats that have died as a result of white nose syndrome. However, some estimate that hundreds of thousands of bats have already disappeared.

The United States Geological Survey says the disease has affected six bat species. They include little brown bats, northern bats, tricolored bats, Indiana bats, small-footed myotis and big brown bats.

Biologists are currently studying possible ways to keep the disease from spreading. Tests are needed to guarantee a plan that will be effective.

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VOICE TWO:

This SCIENCE IN THE NEWS program was written by Mario Ritter and Brianna Blake, who was also our producer. I'm Bob Doughty.

VOICE ONE:

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