▁on ▁the ▁evolution ▁and ▁transmission ▁of ▁e colog ical ▁knowledge ▁and ▁environmental ▁stress ▁in ▁the ▁context ▁of ▁sust ain able ▁development . ▁In ▁response ▁to ▁environmental ▁stress , ▁or ▁inst ability ▁such ▁as ▁political ▁conflict ▁or ▁economic ▁ha z ards ▁he ▁found ▁that ▁traditional ▁knowledge ▁enables ▁local ▁populations ▁to ▁co pe . ▁Ellen ▁the or ised ▁that ▁humans ▁needed ▁to ▁adjust ▁to ▁new ▁conditions , ▁co pe ▁with ▁d angers ▁or ▁improve ▁existing ▁conditions ▁through ▁modifications ▁to ▁their ▁behaviour . ▁He ▁found ▁individuals ▁adapt ▁through ▁their ▁economic ▁and ▁social ▁relationships . ▁ ▁Roy ▁Ellen ' s ▁research ▁helps ▁us ▁understand ▁the ▁ways ▁in ▁which ▁culture ▁and ▁nature ▁are ▁syn erg istic ▁and ▁important ▁to ▁human ▁evolution . ▁Hum ans ▁have ▁used ▁nature ▁by ▁living ▁in ▁it ▁and ▁assim il ating ▁it ▁into ▁culture ▁as ▁we ▁have ▁evol ved . ▁ ▁Roy ▁Ellen ▁is ▁one ▁of ▁the ▁for em ost ▁British ▁anth rop olog ists ▁associated ▁with ▁eth no - bi ology ▁and ▁has ▁made ▁major ▁contributions ▁to ▁field . ▁Ellen ▁helped ▁renew ▁interest ▁in ▁the ▁study ▁of ▁classification ▁with ▁his ▁book ▁" C ategor ical ▁imp ulse : ▁Ess ays ▁on ▁the ▁Anth rop ology ▁of ▁class ifying ▁behavior ” ( 2 0 0 8 ). ▁ ▁In ▁the ▁book ▁he ▁synth es ised ▁the ▁studies ▁of ▁cogn itive ▁and ▁eth no - sci ences ▁with ▁symbol ic ▁anth rop ology ▁providing ▁a ▁hol istic ▁perspective ▁on ▁classification . ▁ ▁Roy ▁Ellen ' s ▁new ▁approach ▁attempted ▁to ▁bridge ▁the ▁gap ▁between ▁the