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1、READINGCOMPREHENSIONTEXTAInthecauseofequalrights,feministshavehadmuchtocomplainabout.Butonestrikingpieceofinequalityhasbeenconvenientlyoverlooked:lifespan.Inthisarea,womenhavetheupperhand.Allroundtheworld,theylivelongerthanmen.Whytheyshoulddosoisnotimmediate
2、lyobvious.Butthesameistrueinmanyotherspecies.Fromlionstoantelopeandfromsealionstodeer,males,forsomereason,simplycanftgothedistance•Onetheoryisthatmalesmustcompeteforfemaleattention.Thatmeansevolutionisbusyselectingforantlers,aggressionandalloywheelsinmales,a
3、ttheexpenseoflongevity.Femalesarenotsubjecttosuchpressures.Ifthistheoryiscorrect,theeffectwillbeespeciallynoticeableinthosespecieswheremalescompetefortheattentionoflotsoffemales.Conversely,itwillbereducedorabsentwheretheydonot.Totestthatidea,TimClutton-Brock
4、ofCambridgeUniversityandKavitaIsvaranoftheIndianInstituteofScienceinBangaloredecidedtocomparemonogamousandpolygynousspecies(inthelatter,amalemonopolisesanumberoffemales)•Theywantedtofindoutwhetherpolygynousmaleshadlowersurvivalratesandagedfasterthanthoseofmo
5、nogamousspecies.Todoso,theycollectedtherelevantdatafor35speciesoflong-livedbirdsandmammals•AstheyreportthisweekinTheProceedingsoftheRoyalSociety,thepatternwasmuchastheyexpected•In16ofthe19polygynousspeciesintheirsample,malesofallagesweremuchmorelikelytodiedu
6、ringanygivenperiodthanwerefemales•Furthermore,theoldertheygot,thebiggerthemortalitygapbecame.Inotherwords,theyagedfaster.Malesfrommonogamousspeciesdidnotshowthesepatterns•Thepointaboutpolygyny,accordingtoDrClutton-Brock,isthatifonemalehasexclusiveaccessto,sa
7、y,tenfemales,anotherninemaleswillbewaitingtotoppletheharemmasterassoonasheshowsthefirstsignofweakness.Theintensecompetitivepressuremeansthatindividualswhosucceedputalltheireffortsintooneortwobreedingseasons.Thatobviouslytakesitstolldirectly.Butamoresubtleeff
8、ectmayalsobeatwork.Moststudentsofageingagreethatananimal1smaximumlifespanissetbyhowlongitcanreasonablyexpecttoescapepredation,disease,accidentanddamagingaggressionbyothersofitskind.Ifitwillhekil