ChangingenvironmentdriveshumanevolutionAseriesofrapidenvironmentalchangesinEastAfricaroughly2millionyearsagomayberesponsiblefordrivinghumanevolution,accordingtoresearchersatPennStateandRutgersUniversity."Thelandscapeearlyhumanswereinhabitingtransitionedrapidlybackandforthbetweenaclosedwoodland（林地）andanopengrasslandaboutfivetosixtimesduringaperiodof200,000years,"saidClaytonMagill,graduatestudentingeosciencesatPennState."Thesechangeshappenedveryabruptly,witheachtransitionoccurringoverhundredstojustafewthousandyears."AccordingtoKatherineFreeman,professorofgeosciences,PennState,thecurrentleadinghypothesissuggeststhatevolutionarychangesamonghumansduringtheperiodtheteaminvestigatedwererelatedtoalong,steadyenvironmentalchangeorevenonebigchangeinclimate."ThereisaviewthistimeinAfricawasthe'GreatDrying,'whentheenvironmentslowlydriedoutover3millionyears,"shesaid."Butourdatashowthatitwasnotagrandprogressiontowardsdry;theenvironmentwashighlyvariable."AccordingtoMagill,manyanthropologists（人类学家）believethatvariabilityofexperiencecantriggercognitivedevelopment."Earlyhumanswentfromhavingtreesavailabletohavingonlygrassesavailableinjust10to100generations,andtheirdietswouldhavehadtochangeinresponse,"hesaid."Changesinfoodavailability,foodtype,orthewayyougetfoodcantriggerevolutionarymechanismstodealwiththosechanges.Theresultcanbeincreasedbrainsizeandcognition,changesinlocomotion（运动，移动）andevensocialchanges--howyouinteractwithothersinagroup.Ourdataareconsistentwiththesehypotheses.Weshowthattheenvironmentchangeddramaticallyoverashorttime,andthisvariabilitycoincideswithanimportantperiodinourhumanevolutionwhenthegenusHomowasfirstestablishedandwhentherewasfirstevidenceoftooluse."变化的环境驱使人类的进化一系列的快速环境变化在非洲东部大约200万年前可能负责驾驶人类进化的研究人员表示,在宾夕法尼亚州立大学和罗格斯大学。“景观早期人类居住迅速之间来回转换一个封闭的林地(林地)和一个开放的草原大约五至六次的时期,200000年,"Clayton称Magill,研究生在宾夕法尼亚州立大学地球科学。“这些变化发生得很突然,每个转换发生在数百到只有几千年。”据凯瑟琳·弗里曼,宾夕法尼亚州立大学地球科学教授,目前的主要假设认为,在人类进化的期间相关的团队调查长期、稳定的环境改变或甚至是一个大的气候的变化。“有一种观点在非洲的这个时候是“伟大的干燥,“当环境慢慢干了