Most of us walk andcarry items in our hands every day.These are seemingly simple activities thatthe majority of us don't question.But an international team of

researchers,includingDr. Richmond from GW's Columbian College of Arts and Sciences,have discoveredthat human walking upright, may have originated millions of years

ago as an adaptationto carrying scarce（稀有的）,high-qualityresources.The team of researchers from the U.S.,England,Japan and Portugalinvestigated the behavior of

modern-daychimpanzees（黑猩猩）as theycompeted for food resources,in an effort to understand what ecological settingswould lead a large ape（类人猿）一one that

resembles the 6million-year old ancestor we shared in common with living chimpanzees一to walk on two legs.

"Thesechimpanzees provide a model of the ecological conditions under which ourearliest ancestors might have begun walking on two legs",said Dr.Richmond.

The researchfindings suggest that chimpanzees switch to moving on two limbs instead of fourin situations where they need to monopolize a resource.Standing on two legs

allows them to carrymuch more at one time because it frees up their hands. Over time , intensebursts of bipedal（二足的）activitymay have led to anatomical（解剖学

的）changes thatin turn became the subject of natural selection where competition for food orother resources was strong.

Two studies wereconducted 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 oftwo different types of nut一the oil palm nut,which is naturally widely available,and the

coula nut,which isnot.The chimpanzees' behavior was monitored in three situations:(a)when onlyoil palm nuts were available,(b)when a small number of coula nuts were

available,and(c)whencoula nuts were the majority available resource.

When the rare coulanuts were available only in small numbers,the chimpanzees transported more atone time.Similarly,when coula nuts were the majority resource,the

chimpanzees ignoredthe oil palm nuts altogether. The chimpanzees regarded the coula nuts as a morehighly-prized resource and competed for them more intensely.

In suchhigh-competition settings,the frequency of cases in which the chimpanzeesstarted moving on two legs increased by a factor of four. Not only was itobvious that

bipedal movementallowed them to carry more of this precious resource,but also that they wereactively trying to move as much as they could in one go by using everything

available一even their mouths.

The second study,byKimberley Hockings of Oxford Brookes University,was a 14-month study of Bossouchimpanzees crop-raiding,a situation in which they have to

compete for rare andunpredictable resources.Here,35 percent of the chimpanzees activity involvedsome sort of bipedal movement,and once again,this behavior appeared to

be linked to a clearattempt to carry as much as possible at one time.Walking on twolimbs and walking on four limbs each have their advantages.

A.Right

B.Wrong

C.Not mentioned