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Most of us walk and carry items in our hands every day.These are seemingly simple activities that the majority of us don't question.But an international team of researchers,including Dr. Richmond from GW's Columbian College of Arts and Sciences,have discovered that human walking upright, may have originated millions of years ago as an adaptation to carrying scarce（稀有的）,high-quality resources.The team of researchers from the U.S.,England,Japan and Portugal investigated the behavior of modern-day chimpanzees（黑猩猩）as they competed for food resources,in an effort to understand what ecological settings would lead a large ape（类人猿）一one that resembles the 6 million-year old ancestor we shared in common with living chimpanzees一to walk on two legs.
"These chimpanzees provide a model of the ecological conditions under which our earliest ancestors might have begun walking on two legs",said Dr. Richmond.
The research findings suggest that chimpanzees switch to moving on two limbs instead of four in situations where they need to monopolize a resource.Standing on two legs allows them to carry much more at one time because it frees up their hands. Over time , intense bursts of bipedal（二足的）activity may have led to anatomical（解剖学的）changes that in turn became the subject of natural selection where competition for food or other resources was strong.
Two studies were conducted by the team in Guinea. The first study was conducted by the team in Kyoto University's "outdoor laboratory" in a natural clearing in Bossou Forest. Researchers allowed the wild chimpanzees access to different combinations of two different types of nut一the oil palm nut,which is naturally widely available,and the coula nut,which is not.The chimpanzees' behavior was monitored in three situations:(a)when only oil palm nuts were available,(b)when a small number of coula nuts were available,and(c)when coula nuts were the majority available resource.
When the rare coula nuts were available only in small numbers,the chimpanzees transported more at one time.Similarly,when coula nuts were the majority resource,the chimpanzees ignored the oil palm nuts altogether. The chimpanzees regarded the coula nuts as a more highly-prized resource and competed for them more intensely.
In such high-competition settings,the frequency of cases in which the chimpanzees started moving on two legs increased by a factor of four. Not only was it obvious that bipedal movement allowed them to carry more of this precious resource,but also that they were actively trying to move as much as they could in one go by using everything available一even their mouths.
The second study,by Kimberley Hockings of Oxford Brookes University,was a 14-month study of Bossou chimpanzees crop-raiding,a situation in which they have to compete for rare and unpredictable resources.Here,35 percent of the chimpanzees activity involved some sort of bipedal movement,and once again,this behavior appeared to be linked to a clear attempt to carry as much as possible at one time.
Walking on two limbs and walking on four limbs each have their advantages.
A.Right
B.Wrong
C.Not mentioned
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Most Adults in US Have Low Risk of Heart Disease
More than 80 percent of US adults have a less than 10-percent risk of developing heart disease in the next 10 years,according to a report in the Journal of the American College of Cardiology.Just 3 percent have a risk that exceeds 20 percent.
"I hope that these numbers will give physicians,researchers,health policy analysts,and others a better idea of how coronary heart disease is distributed in the US population,"lead author Dr.Earl S.Ford,from the Centers for Disease Control and Prevention in Atlanta,said in a statement.
The findings are based on analysis of data from 13,769 subjects,between 20 and 79 years of age,who narticipated in the Third National Health and Nutrition Examination Survey from 1988 to 1994.
Overall,82 percent of adults had a risk of less than 10 percent,15 percent had a risk that fell between 10 to 20 percent,and 3 percent had a risk above 20 percent.
The proportion of subjects in the highest risk group increased with advancing age,and men were more likely than women to be in this group.By contrast,race or ethnicity had little effect on risk distributions.
Although the report suggests that most adults have a low 10-year risk of heart disease,a large proportion have ahigh or immediate risk,Dr.Daniel S.Berman,from Cedars-Sinai Medical Center in Los Angeles,and Dr.Nathan
D.Wong,from the University of California at Irvine,note in a related editorial.
Aggressive treatment measures and public health strategies are needed to shift the overall population risk downward,they add.
The main purpose of the passage is to______.
A.introduce that most adults in US adults have low risk of heart disease
B.give treatment measures to reduce the risk of developing heart disease for US adults
C.describe the research made by the Centers for Disease Control and Prevention
D.warn people that they should pay attention to the threat of heart disease immediately
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US Blacks Hard-hit by Cancer
Death rates for cancer are falling for all Americans,but black Americans are still more likely to die of cancer than whites,the American Cancer Society said Monday.
In a special report on cancer and blacks,the organization said blacks are usually diagnosed with cancer later than whites,and they are more likely to die of the disease.
This could be because of unequal access to medical care,because blacks are more likely to have other diseases like diabetes as well,and perhaps because of differences in the biology of the cancer itself,the report added.
“In general,African Americans have less likelihood of surviving five years after diagnosis than whites for all cancer sites and all stages of diagnosis,”the report said.
“In describing cancer statistics for African Americans,this report recognizes that socioeconomic disparities and unequal access to medical care may underlie many of the differences associated with race.”
The Cancer Society said blacks should be encouraged to get check-ups earlier,when cancer was more treatable,and it said more research is needed to see if biological differences play a role.
“The new statistics emphasize the continuing importance of eliminating these social disparities through public policy and education efforts,”the organization said in a statement.
But it also noted a drop in cancer death rates.
“Cancer death rates in both sexes for all sites combined have declined substantially among black Americans since 1992,as have incidence rates,”said the report.
“Increased efforts to improve economic conditions in combination with education about the relationship of lifestyle choices to cancer could further reduce the burden of cancer among African Americans.” About 36 million Americans describe themselves as black,representing about 12 percent of the population.
Cancer can be treated easier if it is detected
A.in an early stage
B.together with other diseases
C.during check-ups
D.in elderly people
