请问这段英语中的even用做什么词类,MoroccoandCaliforniaarebitsoftheEarthinverysimilarlatitudes,bothonthewestcoastsofcontinentswithsimilarclimates,andprobablywithrathersimilarnaturalresources.Yettheirpresentdev

　　请问这段英语中的even用做什么词类,

　　MoroccoandCaliforniaarebitsoftheEarthinverysimilarlatitudes,bothonthewestcoastsofcontinentswithsimilarclimates,andprobablywithrathersimilarnaturalresources.Yettheirpresentdevelopmentiswhollydifferent,notsomuchbecauseofdifferentpeopleeven,butbecauseofthedifferentthoughtsthatexistinthemindsoftheirinhabitants.