3   mill ion ▁in ▁ 2 0 0 5 . ▁In ▁the ▁last ▁three ▁dec ades ▁of ▁the ▁ 1 6 th ▁century , ▁the ▁population ▁of ▁present - day ▁Mexico ▁dropped ▁to ▁about ▁one   mill ion ▁people . ▁The ▁May a ▁population ▁is ▁today ▁estimated ▁at ▁six ▁million , ▁which ▁is ▁about ▁the ▁same ▁as ▁at ▁the ▁end ▁of ▁the ▁ 1 5 th ▁century , ▁according ▁to ▁some ▁estimates . ▁ ▁In ▁what ▁is ▁now ▁Brazil , ▁the ▁ind igen ous ▁population ▁decl ined ▁from ▁a ▁pre - Col umb ian ▁high ▁of ▁an ▁estimated ▁four ▁million ▁to ▁some ▁ 3 0 0 , 0 0 0 . ▁ ▁While ▁it ▁is ▁difficult ▁to ▁determine ▁exactly ▁how ▁many ▁N atives ▁lived ▁in ▁North ▁America ▁before ▁Columb us , ▁estimates ▁range ▁from ▁a ▁low ▁of ▁ 2 . 1 ▁million ▁to ▁ 7 ▁million ▁people ▁to ▁a ▁high ▁of ▁ 1 8 ▁million . ▁ ▁The ▁ab original ▁population ▁of ▁Canada ▁during ▁the ▁late ▁ 1 5 th ▁century ▁is ▁estimated ▁to ▁have ▁been ▁between ▁ 2 0 0 , 0 0 0 ▁and ▁two ▁million , ▁with ▁a ▁figure ▁of ▁ 5 0 0 , 0 0 0 ▁currently ▁accepted ▁by ▁Canada ' s ▁Royal ▁Commission ▁on ▁Ab original ▁Health . ▁Re pe ated ▁out break s ▁of ▁Old ▁World ▁inf ect ious ▁dise ases ▁such ▁as ▁influen za , ▁meas les ▁and ▁small po x ▁( to ▁which ▁they ▁had ▁no ▁natural ▁imm unity ), ▁were ▁the ▁main