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1、WhatpromptedearlyhumanstoleaveAfricaforthefirsttimeDiscussiononthereasonsandevidenceforthefirsttimethatearlyhumansleftAfricaIntroductionThispaperdiscussesthetopicofnofactorcanexplainthefirsttimethatearlyhumansleftAfrica.Earlyhumansareancienthumansintheearlystageofhumanevolutionfromapestohumans,inclu
2、dingthehumanoidanimalsatthistime.ThefirstdeparturefromAfricareferstothefirstoutwardmigrationofearlyhumanbeingsfromtheAfricancontinent.ThispaperdiscussestheevidenceandreasonsofearlyhumanleavingAfricaforthefirsttimefromthreeaspects:thetestimonyprovidedbyhumanfossils,theevidenceprovidedbyclimatechangea
3、ndthetestimonyprovidedbyhumangeneticmappinganalysis.Thispaperbelievesthattheestablishmentoftheperiodofhumanfossilsandhumanremainsbyarchaeologistscancorroborateeachotherwiththeclimateanalysisandhumangenemapextensionofpaleoclimatology,andcanprovethatearlyhumansleftAfricaforthefirsttimeduetoclimatechan
4、geanddeteriorationoflivingenvironment,andspreadtotheEurasiancontinentandotherterritories.1. DirectevidencefromhumanfossilsHumanfossilsareallthathumanancestorsleftintheworld,andarealsoimportantevidencetorevealthepathandcauseofhumanmigration.In1924,archaeologistsfoundtheoldestancienthumanfossilinalime
5、stonecaveinDrimolen,nearJohannesburg,SouthAfrica,andnameditAustralopithecusAfricanus.Amongmorethan900ancienthumanremains,oneofthemwas3millionyearsago(Dennell,Roebroeks,2005).In1990,researchersfoundtheearliestancienthumanfossilsattheDemanisisiteinGeorgia,whichwereearlierthanthoseinAfrica.Theseskullfo
6、ssilsandbonefossilshavebeenprovedthatancienthumansatthattimewereveryshort,only1.5meterstall,andthebraincapacitywasonlyonethirdofthatofmodernhumans(Agust,Lordkipanidze,2011).TheemergenceoftheDemanianancientsextendedtheearliesttimeofhumanexistenceinAsiato1.8millionyearsago.Later,archaeologistsfoundthe
7、earliestEuropeanfossilsatthearchaeologicalsiteofAtapulcainSpain,whicharehumantoothbonesdatingmorethan1.4millionyearsago(Forster,Matsumura,2005).Accordingtothetimejudgmentofarchaeologistsonthefossilsofancientapesandhumans,noearlierhumanfossilremainshavebeenfoundonthecontinentoutsideAfrica.Fromtheevid
8、enceprovidedbyancienthumanfossils,asearlyas2.5MaBPto3.0MaBPthereweresignsofancienthumanandhumanlifeinAfrica.TheearliestsurvivaltimeofhumanintheSouthCaucasuswas1.7MaBPto1.8MaBP,whiletheevidenceoftheearliesthumanlifeinWesternEuropecouldbeextendedto1.4MaBP(Derricourt,2005).Accordingtothetimejudgmentofa
9、rchaeologistsonthefossilsofancientapesandhumans,noearlierhumanfossilremainshavebeenfoundonthecontinentoutsideAfrica.TheevidenceprovidedbyancienthumanfossilsshowsthattheancienthumanfossilsinthesouthernCaucasusandwesternEuropearemoreadvancedthanthoseofAfricanancienthumansintermsofbraincapacity,heighta
10、ndotheraspects,althoughtheseancienthumansarestillverybackwardcomparedwiththebraincapacity,heightandphysicalabilityofmodernhumans.ThetimepointoftheappearanceofancienthumanfossilscaneffectivelyprovethatAfricansfirstappearedancienthumansandbecametheearliestancestorsofmankind.Stonesandotherearlyinstrume
11、ntsunearthedfromarchaeologicalsitescanalsoprovethatancienthumansandhumanoidanimalslivinginAfricagatheredandmigratedduringtheprocessofforagingandhunting.ThereisnoevidenceofearlierhumanandanimalproliferationinothercontinentsexceptAfrica(Balter,Gibbons,2020).Atthesametime,alargenumberoffossilsfromtheSo
12、uthAfricanGardenfoundintheEastAfricanRiftValley,theeastbankofLakeTurnerinKenya,andtheTanzanianValleyhaveprovedthattheyhavetheabilitytowalkuprightandusesimpletools.TheseevidencescanprovethatearlyhumanbeingshavetheabilitytomigrateandliveingroupsforlongdistancesinAfrica.Itcanthelpthinkingthatearlyhuman
13、beingssetoutfromtheAfricancontinentandcrossedthedesertnorthward,enteredtheCaucasusfromSuez,andfurthermigratedtoIndiaandWesternEurope.ThestoneaxeandothertoolsunearthedinGeorgiaevenprovedthatearlyhumanshadbeenverycruelandviciousintheprocessofleavingtheAfricancontinentandmigratingtotheMiddleEast.Theyev
14、endirectlycompetedwithwildcarnivoresforfood.Therefore,thechronologicalsequence,evolutionarycharacteristicsandthecharacteristicsoftoolsusedbyearlyhumansexcavatedbyarchaeologistsfromallovertheworldcansupporteachotherandsupporttheviewthatearlyhumansleftAfricaforthefirsttime.2. Climatetransformationmake
15、smankindleaveAfricaClimatechangeforcedearlyhumanstoleaveAfricaandbegintomigratebychangingthelivingenvironmentofhumans.AccordingtotheresearchofQuaternarypaleoclimatologists,theglobalpaleoclimatehasundergonesignificantadjustmentbetween2.5and2.8MaBRAtthistime,theearthenteredtheQuaternaryIceAge(Thomas,B
16、urrough,2012).MostofEuropeandNorthAmericabegantofreezerapidly,andmostofthelandinthenorthernhemispherewascoveredbyglaciers.TheScandinavianGlacierCenter,SiberianGlacierCenterandGreenlandGlacierCenterinthenorthernhemispherebegantoextendtothesouth(Timmermann,Friedrich,2016).Theexpansionofglaciersinthenorthernhemispherehasmadetheclimatemovesouthward.Atthesametime,theclimateoftheAfricancontinentbegantobecomeunusuallydry,andtheairhumidityandprecipitationonthecontinentdecreasedrapidly.T
