▁over to ok ▁the ▁use ▁of ▁the ▁spe ar ▁and ▁at lat l , ▁and ▁agricult ural ▁production ▁of ▁the ▁" Three ▁Sister s " ▁( ma ize , ▁be ans , ▁and ▁squ ash ) ▁was ▁introduced . ▁While ▁full ▁scale ▁int ensive ▁agricult ure ▁did ▁not ▁begin ▁until ▁the ▁following ▁Mississ ipp ian ▁period , ▁the ▁beginning ▁of ▁serious ▁cultiv ation ▁greatly ▁supp lement ed ▁the ▁gather ing ▁of ▁plants . ▁ ▁Late ▁Wood land ▁settlement s ▁became ▁more ▁numerous , ▁but ▁the ▁size ▁of ▁each ▁one ▁( with ▁exceptions ) ▁was ▁smaller ▁than ▁their ▁middle ▁Wood land ▁counter parts . ▁The ▁reasons ▁for ▁this ▁are ▁unknown , ▁but ▁it ▁has ▁been ▁the or ized ▁that ▁populations ▁increased ▁so ▁much ▁that ▁trade ▁alone ▁could ▁no ▁longer ▁support ▁the ▁communities ▁and ▁some ▁cl ans ▁res orted ▁to ▁ra iding ▁others ▁for ▁resources . ▁Alternatively , ▁the ▁efficiency ▁of ▁b ows ▁and ▁ar rows ▁in ▁hunting ▁may ▁have ▁dec im ated ▁the ▁large ▁game ▁animals , ▁forcing ▁the ▁tribes ▁to ▁break ▁apart ▁into ▁smaller ▁cl ans ▁to ▁better ▁use ▁local ▁resources , ▁thus ▁limit ing ▁the ▁trade ▁potential ▁of ▁each ▁group . ▁A ▁third ▁possibility ▁is ▁a ▁col der ▁climate ▁may ▁have ▁affected ▁food ▁yields , ▁possibly ▁affected ▁by ▁Northern ▁Hem is phere ▁extreme ▁weather ▁events ▁of ▁ 5 3 5 – 5 3 6 , ▁also ▁limit ing ▁trade ▁possibilities . ▁Last ly , ▁it ▁may ▁be ▁that ▁agricult ural ▁technology ▁became ▁s oph istic ated ▁enough ▁that ▁c rop ▁variation ▁between