2013职称英语(理工类a和b)新增文章a

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1、第四十八篇ResearchersDiscoverWhyHumansBeganWalkingUprightMostofuswalkandcarryitemsinourhandseveryday.Theseareseeminglysimpleactivitiesthatthemajorityofusdon’tquestion.Butaninternationalteamofresearchers,includingDr.RichmondfromGW'sColumbianCollegeofArtsandSciences，havediscoveredthathumanwalkinguprigh

2、t,mayhaveoriginatedmillionsofyearsagoasanadaptationtocarryingscarce,high-qualityresources.TheteamofresearchersfromtheU.S.,England,JapanandPortugalinvestigatedthebehaviorofmodern-daychimpanzeesastheycompetedforfoodresources，inanefforttounderstandwhatecologicalsettingswouldleadalargeape—onethatres

3、emblesthe6million-yearoldancestorwesharedincommonwithlivingchimpanzees—towalkontwolegs.“Thesechimpanzeesprovideamodeloftheecologicalconditionsunderwhichourearliestancestorsmighthavebegunwalkingontwolegs,"，saidDr.Richmond.Theresearchfindingssuggestthatchimpanzeesswitchtomovingontwolimbsinsteadoff

4、ourinsituationswheretheyneedtomonopolizearesource.Standingontwolegsallowsthemtocarrymuchmoreatonetimebecauseitfreesuptheirhands.Overtime，intenseburstsofbipedalactivitymayhaveledtoanatomicalchangesthatinturnbecamethesubjectofnaturalselectionwherecompetitionforfoodorotherresourceswasstrong.Twostud

5、ieswereconductedbytheteaminGuinea.ThefirststudywasconductedbytheteaminKyotoUniversity’s“outdoorlaboratory”inanaturalclearinginBossouForest.Researchersallowedthewildchimpanzeesaccesstodifferentcombinationsoftwodifferenttypesofnut—theoilpalmnut，whichisnaturallywidelyavailable,andthecoulanut,whichi

6、snot.Thechimpanzees’behaviorwasmonitoredinthreesituations:(a)whenonlyoilpalmnutswereavailable,(b)whenasmallnumberofcoulanutswereavailable，and(c)whencoulanutswerethemajorityavailableresource.Whentherarecoulanutswereavailableonlyinsmallnumbers,thechimpanzeestransportedmoreatonetime.Similarly,whenc

7、oulanutswerethemajorityresource,thechimpanzeesignoredtheoilpalmnutsaltogether.Thechimpanzeesregardedthecoulanutsasamorehighly-prizedresourceandcompetedforthemmoreintensely.Insuchhigh-competitionsettings，thefrequencyofcasesin