2004-1-12
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VOICE ONE:
This is SCIENCE IN THE NEWS, in VOA Special English. I'm Bob
Doughty.
VOICE TWO:
And I'm Sarah Long. This week -- fossils help bring light to a
mysterious time in prehistoric Africa.
VOICE ONE:
New findings about air pollution: Could it be worse for the heart
than the lungs?
VOICE TWO:
And, in the United States, the government acts to ban a
weight-loss product.
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VOICE ONE:
Researchers say they have identified animal fossils from
twenty-seven-million years ago in what is now Ethiopia. The remains
are from the middle of a time called the "missing years" or the
"dark period." This is because scientists have so little information
about the mammals that lived then.
The period began thirty-two-million years ago. Africa and Arabia
were a single continent, a huge island known as Afro-Arabia. The
period ended twenty-four-million years ago, after a land bridge
formed with Eurasia.
VOICE TWO:
John Kappelman is an anthropologist at the University of Texas in
Austin and leader of the American and Ethiopian search team. Mister
Kappelman says eight million years is a long time to lack
information about a continent. He says scientists have only been
able to guess what happened to African mammals during that period.
The remains found in the Chilga area of Ethiopia offer important
evidence.
VOICE ONE:
The remains include teeth, skull pieces and other bones. The
scientists found them in a farming area about two-thousand meters
above sea level, in the highlands of Ethiopia. Satellite pictures
helped the researchers decide where to dig. The fossils came from
about seventy different digs. The magazine Nature published the
findings.
The scientists say the fossils come from before large numbers of
animals began to arrive in Africa from Europe and Asia. The fossils
also show that some animals existed millions of years before
scientists had thought.
VOICE TWO:
The researchers found several kinds of ancient proboscideans.
These are animals with trunks. Modern elephants are proboscideans.
Scientists have long thought elephants began in Africa. They say
this discovery proves that theory. The ancestors weighed about
one-thousand kilograms, a lot smaller than African elephants today.
John Kappelman says the elephant ancestors were one of the few
African mammals that survived the invasion of mammals from Eurasia.
He says elephants got their start in Africa during the
eight-million-year period, and then spread around the world.
VOICE ONE:
The researchers also found the
remains of an ancient animal with two horns on its head, called the
arsinoithere. The scientists were excited, because this is the
youngest set of such remains yet discovered. The animal is much
larger than its ancestors. Earlier forms were about the size of
pigs. But the arsinoithere found at Chilga was about two meters tall
and weighed more than two tons.
They were similar to the modern rhinoceros. The two are not
related. In fact, scientists thought arsinoitheres had disappeared
from the Afro-Arabian continent once rhinos arrived from Eurasia.
One researcher says it now appears they did not compete for
survival.
Scientists say they expect more discoveries to come about the
mammals that lived during the so-called missing years.
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VOICE TWO:
A study finds that air pollution is worse for the heart than the
lungs.The American Heart Association published the findings in its
magazine, Circulation.
Researchers used information given by more than half-a-million
adults between nineteen-eighty-two and nineteen-ninety-eight. The
information is from a continuing study by the American Cancer
Society on cancer prevention. The study included people thirty and
older living in cities where officials kept records on air
pollution.
VOICE ONE:
During the sixteen-year period, one in five of the people in the
study died. The scientists found that heart disease caused about
forty-five percent of the deaths. Only eight percent of the people
died from diseases of the breathing system.
The researchers compared the information with air pollution
records from more than one-hundred-fifty cities. The scientists
controlled for things that increase the risk of heart disease, like
smoking and being overweight. Still, they found a stronger link
between air pollution and heart disease than respiratory disease.
VOICE TWO:
Arden Pope of Brigham Young University in Provo, Utah, led the
study. He says air pollution is not the main cause of heart disease.
But, he says, breathing polluted air causes swelling and worsens
disease in the arteries of the blood system. He says this affects
the ability of the heart to operate effectively. The study also
suggests that air pollution harms the nervous system, leading to
abnormal heartbeat.
The study involved air polluted by
small particles of soot. Vehicles that use diesel fuel create a lot
of soot. So do some factories. But it is also released into the air
by burning wood and other substances including animal waste and
vegetable oil for fuel.
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VOICE ONE:
Soot was cause for a different concern in another recent study.
Scientists with the American space agency, NASA, suggest it as a
major cause of global warming. The NASA researchers say soot may be
responsible for twenty-five percent of global warming observed over
the past century.
With computers they recreated the effects of industrial gases and
other influences on world climate. They say carbon dioxide and other
gases that trap heat have been the main cause of recent global
warming, and will remain so. Still, they say soot may be worse than
has been thought.
The study says the problem is how soot interacts with snow and
ice.
VOICE TWO:
Snow and ice have highly reflective surfaces. A lot of the
sunlight that hits them is forced back up toward the sky. This helps
prevent melting. But the scientists say the problem develops when
snowflakes pick up fine particles of soot as they fall. The black
carbon in soot reduces the ability of snow and ice to reflect
sunlight. Instead, the black soot absorbs the energy and warmth, and
causes melting.
James Hansen and Larissa Nazarenko of the Goddard Institute for
Space Studies reported the findings. They estimate that soot
particles in snow reduced reflectivity by three percent in northern
land areas of the world. Their estimate for the Arctic is
one-and-a-half percent.
VOICE ONE:
The scientists say the soot causes the melting season of glaciers
to begin earlier and last longer. This has a large effect, they say,
because wet snow is much darker than dry snow. So the problem
increases.
The scientists estimate that soot is two times as effective as
carbon dioxide in changing surface air temperatures. But they say
the good news is that cleaner diesel engines and other technologies
are being developed to reduce soot.
The study is in the Proceedings of the National Academy of
Sciences.
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VOICE TWO:
In the United States, the government is acting to ban the sale of
ephedra as a product to help people lose weight. Ephedra is a plant
that contains ephedrine and pseudoephedrine. These substances can
increase a person's energy level and cause weight loss. However,
officials warn that ephedra also raises blood pressure. Ephedra has
been linked to heart attacks, strokes, seizures and deaths.
The secretary of Health and Human Services announced the ban.
Tommy Thompson urged people to stop using ephedra even before the
ban takes effect. He said he did not want to delay the announcement,
because people often try to lose weight at the start of a new year.
VOICE ONE:
The market has grown sharply for herbal products known as dietary
supplements. Companies do not have to prove them safe and effective
the way drug makers do. In nineteen-ninety-four, Congress limited
the ability of the Food and Drug Administration to take action
against supplements. This is the first ban since then.
The ban will not include the version of ephedra used in medicines
to treat breathing infections. Ephedra has long been used for this
purpose as a traditional medicine in China, where the plant is
called ma huang.
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VOICE TWO:
SCIENCE IN THE NEWS was written by Caty Weaver and produced by
Cynthia Kirk. I'm Sarah Long.
VOICE ONE:
And, I'm Bob Doughty. Join us again next week for another program
about science in Special English on the Voice of America.