▁years ▁ago ▁this ▁rock ▁shelter ▁was ▁used ▁for ▁long - term ▁based ▁cam ps ▁by ▁several ▁families ▁which ▁were ▁involved ▁in ▁activities ▁of ▁every day ▁life ; ▁and , ▁by ▁around ▁ 4 , 0 0 0 ▁years ▁ago ▁evidence ▁found ▁in ▁the ▁sed iment ▁layers ▁suggests ▁the ▁site ▁was ▁again ▁used ▁by ▁small ▁hunting ▁parties ▁as ▁a ▁short - term ▁camp . ▁There ▁tools ▁included ▁con ca ve ▁project ile ▁points , ▁sc rap ers , ▁cho ppers , ▁ham mer ▁stones , ▁and ▁b one ▁aw ls . ▁Ev idence ▁has ▁shown ▁that ▁during ▁occupation , ▁the ▁inhabitants ▁had ▁a ▁di et ▁that ▁consisted ▁of ▁de er , ▁racc oon , ▁op os sum , ▁birds , ▁and ▁fish . ▁ ▁Many ▁of ▁the ▁foot paths ▁leading ▁to ▁these ▁c aves ▁still ▁exist , ▁although ▁they ▁are ▁almost ▁impossible ▁to ▁access ▁due ▁to ▁d eter ior ation . ▁ ▁Arch ae ological ▁history ▁The ▁Mod oc ▁Rock ▁Sh elter ▁site ▁was ▁discovered ▁in ▁ 1 9 5 1 ▁by ▁arch ae ologist ▁Ir win ▁Pe ith mann , ▁who ▁is ▁known ▁for ▁teaching ▁himself ▁about ▁the ▁custom s ▁of ▁Native ▁Americans ▁by ▁living ▁among ▁them . ▁ ▁See ▁also ▁List ▁of ▁arch ae ological ▁sites ▁on ▁the ▁National ▁Register ▁of ▁Historic ▁Places ▁in ▁Illinois ▁List ▁of ▁National ▁Historic ▁Land marks ▁in ▁Illinois ▁National ▁Register ▁of ▁Historic ▁Places ▁list ings ▁in ▁Rand olph ▁County , ▁Illinois ▁ ▁References ▁ ▁Category : Ar cha ic ▁period ▁in ▁North ▁America ▁Category : Arch ae