为什么进化后的人类毛发稀疏？而和我们人类最近似的动物王国里的亲戚则仍全身匹着毛发？在物种进化过程中，毛发稀疏的人类是如何确保自己能成功生存下来？本期《随身英语》谈论毛发和人类进化的关系。
词汇:Evolution进化
ComparedtootherlargemammalsonEarth,wehumanshaverelativelylittlehair.Thisobviousfactisnotsostrangeuntilwelookatourclosestlivingrelativesintheanimalkingdom–chimpanzeesandothergreatapes.Why,mightweask,haveweevolvedtobealmosthairlesswhenallotherprimatesarestillcoveredinfurInfact,bizarreasitmayseem,ourlackofhairhasbeenthekeytoourevolutionarysuccessasaspecies.
Thequestionwhyourearliestancestorslosttheirhairwhenfurwouldhavebeenbeneficialtothem–forkeepingwarmoncoldnights,forexample–wasponderedbyCharlesDarwin,thefamousevolutionist:"Noonesupposesthatthenakednessoftheskinisanydirectadvantagetoman."Heconcludedthatthereasonhomininslosttheirhairwassexualselection.Inotherwords,wepreferourpartnerstohavelittlehair.Butwhatcausedourancestorstostartlosingtheirhairbeforethispreferencesetin
Themostlikelyhypothesistoexplainthelossofhairisthatitbecamenecessarywhenearlyhominidsmovedtoamoreopensavannahhabitataround2to3millionyearsago,whentheystartedtohuntbiggame.Huntinginopensavannahmeantbeingexposedtothestrongheatofthesunforseveralhoursinthedayandbeingindangerofoverheating.Beingcoveredinhairpreventedourancestorsfromlosingheatfastenough.So,asPeterWheeler,ofLiverpoolJohnMooresUniversityintheUK,explained,losinghairallowedthemtodeveloptheabilitytosweatandthereforetocooldown.Earlyhumanscould,asaconsequence,beoutatmiddayhuntingandforaging."Itwouldbe[an]enormousadvantagetobeabletospendtheentiremiddayforaging,findingmatesorfightingenemies",TamásDávid-BarrettofOxfordUniversitysays."Sweatingallowsthat,andforsweattobeefficientyouneedtobemostlyhairless".Themeatfromhuntinganimalsgaveearlyhumanstheenergytofueltheirgrowingbrain.
primates灵长目动物bizarre奇怪的，离奇的species（动植物的）物种toponder思索，考虑evolutionist进化论者nakedness裸露hominins古人类sexualselection雌雄淘汰ancestor祖先hypothesis假说，假设hominids原人savannah稀树草原tohunt打猎game野禽earlyhuman早期人类foraging觅食，搜寻食物findamate寻找配偶gland腺propensity习性，倾向tothrive长得健壮torso（人体的）躯干
1.阅读课文并回答问题。
1.TrueorfalseAllprimatesarecoveredinfur.
2.WhowasCharlesDarwin
3.Whywasmovingtothesavannahaproblemforourearlyancestors
4.Whatistheadvantageofhavinglittlehairinahotclimate
5.Whatlinkdoestheauthormakebetweenhuntingmeatandhumansuccess
2.请你在不参考课文的情况下完成下列练习。选择一个意思合适的单词填入句子的空格处。
directclosegoodnear
revolutionaryevolutionaryevolutionextraordinary
3.Ifbabiesweartoomanyclothesinhotweather,theyareat__________ofoverheating.
riskdangerlikelypossibility
thrivesatthrivesonthriveswiththriveon
5.Ourhumanancestorslosthairbecausethisallowedthemtosweatwiththegreatest__________.
effortdeficiencyefficiencysufficiency
1.TrueorfalseAllprimatesarecoveredinfur.False.Humansonlyhavealittlehairontheirbodiescomparedtootherprimates.
2.WhowasCharlesDarwinHewasafamousevolutionist.
3.WhywasmovingtothesavannahaproblemforourearlyancestorsBecauseitmeantthattheywereexposedtolonghoursofstrongsunandtheywereindangerofoverheating.
4.WhatistheadvantageofhavinglittlehairinahotclimateItmeansthatyoucansweatefficiently.
5.WhatlinkdoestheauthormakebetweenhuntingmeatandhumansuccessTheauthorexplainsthateatingmeatprovidedenergythathelpedthebraintodevelop.
3.Ifbabiesweartoomanyclothesinhotweather,theyareatriskofoverheating.
4.Danielthrivesonhardwork.
5.Ourhumanancestorslosthairbecausethisallowedthemtosweatwiththegreatestefficiency.