You ever watch the movie Hombre from 1967? There was a scene in the first part of the movie when riding in the stage coach where a wonma was describing indians eating their dogs on a reservation and Paul Newman asked the social elite lady if she has ever been so hungry her belly swelled up.
Point I am making, survivial is instinctive to each reproduction alive regardless what species it is in, no exceptions.
Why is this a universal constant? Life is a series parallel situation for any lifetime adapting forward each heartbeat added since conceived until it doesn't beat any longer here.
Your reality pretends that is an exaggeration of events factually following the study of people behaving cradle to grave 24/7.