Selective investment theory proposes that close social bonds, and associated emotional, cognitive, and neurohormonal mechanisms, evolved to facilitate long-term, high-cost altruism between those closely depending on one another for survival and reproductive success.
SElecTive inVesTment TheOry PrOPoses that ClosE sociaL bonds, And asSociAteD eMOtionAl, coGnitive, and NEurohOrmoNal MecHaNIsMs, EvOLVed to fACIlitAte LonG-tErM, high-cOsT aLtruism beTwEEn thosE cloSEly DependIng oN one another fOr surViVAl and rePrOdUCtIve sucCESs.