▁C aus al ▁role ▁theories ▁of ▁bi ological ▁function ▁trace ▁their ▁origin ▁back ▁to ▁a ▁ 1 9 7 5 ▁paper ▁by ▁Robert ▁C umm ins . ▁C umm ins ▁defines ▁the ▁functional ▁role ▁of ▁a ▁component ▁of ▁a ▁system ▁to ▁be ▁the ▁caus al ▁effect ▁that ▁the ▁component ▁has ▁on ▁the ▁larger ▁containing ▁system . ▁For ▁example , ▁the ▁heart ▁has ▁the ▁actual ▁caus al ▁role ▁of ▁p ump ing ▁blood ▁in ▁the ▁circul atory ▁system ; ▁therefore , ▁the ▁function ▁of ▁the ▁heart ▁is ▁to ▁p ump ▁blood . ▁This ▁account ▁has ▁been ▁object ed ▁to ▁on ▁the ▁grounds ▁that ▁it ▁is ▁too ▁loose ▁a ▁notion ▁of ▁function . ▁For ▁example , ▁the ▁heart ▁also ▁has ▁the ▁caus al ▁effect ▁of ▁producing ▁a ▁sound , ▁but ▁we ▁would ▁not ▁consider ▁producing ▁sound ▁to ▁be ▁the ▁function ▁of ▁the ▁heart . ▁▁ ▁Selected ▁effect ▁▁ ▁Selected ▁effect ▁theories ▁of ▁bi ological ▁functions ▁hold ▁that ▁the ▁function ▁of ▁a ▁bi ological ▁trait ▁is ▁the ▁function ▁that ▁the ▁trait ▁was ▁selected ▁for , ▁as ▁argued ▁by ▁Ruth ▁Mill ikan . ▁For ▁example , ▁the ▁function ▁of ▁the ▁heart ▁is ▁p ump ing ▁blood , ▁for ▁that ▁is ▁the ▁action ▁for ▁which ▁the ▁heart ▁was ▁selected ▁for ▁by ▁evolution . ▁In ▁other ▁words , ▁p ump ing ▁blood ▁is ▁the ▁reason '' ▁that ▁the ▁heart ▁has ▁evol ved . ▁This ▁account ▁has ▁been ▁critic ized ▁for ▁being ▁too ▁restrict ive ▁a ▁notion ▁of ▁function . ▁It ▁is ▁not ▁always ▁clear ▁which ▁behavior ▁has ▁contributed ▁to