ates ▁David ▁H ume , ▁a ▁member ▁of ▁staff ▁at ▁the ▁Royal ▁Botan ic ▁Garden ▁Edinburgh , ▁who ▁died ▁at ▁the ▁Battle ▁of ▁M ons ▁in ▁ 1 9 1 4 . ▁ ▁E volution ▁and ▁ph y log eny ▁ ▁The ▁family ▁Z ing iber aceae ▁is ▁mainly ▁tropical ▁in ▁distribution . ▁The ▁unusual ▁mountain ous ▁distribution ▁of ▁Ros co ea ▁may ▁have ▁evol ved ▁relatively ▁recently ▁and ▁be ▁a ▁response ▁to ▁the ▁u pl ift ▁taking ▁place ▁in ▁the ▁region ▁in ▁the ▁last ▁ 5 0 ▁million ▁years ▁or ▁so ▁due ▁to ▁the ▁collision ▁of ▁the ▁Indian ▁and ▁Asian ▁t ect onic ▁pl ates . ▁ ▁Species ▁of ▁Ros co ea ▁divide ▁into ▁two ▁clear ▁groups , ▁a ▁H imal ay an ▁cla de ▁and ▁a ▁" Ch inese " ▁cla de ▁( which ▁includes ▁some ▁species ▁from ▁outside ▁China ). ▁The ▁two ▁cl ades ▁correspond ▁to ▁a ▁ge ographical ▁separation , ▁their ▁main ▁distributions ▁being ▁divided ▁by ▁the ▁Bra h map ut ra ▁River ▁as ▁it ▁flows ▁south ▁at ▁the ▁end ▁of ▁the ▁H imal ay an ▁mountain ▁chain . ▁It ▁has ▁been ▁suggested ▁that ▁the ▁genus ▁may ▁have ▁origin ated ▁in ▁this ▁area ▁and ▁then ▁spread ▁west wards ▁along ▁the ▁H imal ay as ▁and ▁east wards ▁into ▁the ▁mountains ▁of ▁China ▁and ▁its ▁southern ▁neighb ours . ▁R . ▁h ume ana ▁falls ▁into ▁the ▁Chinese ▁cla de ▁as ▁would ▁be ▁expected ▁from ▁its ▁distribution . ▁ ▁It ▁is ▁closely ▁related ▁to ▁R . ▁c aut ley o