The so-called "grandmother hypothesis", based on studies of African hunter-gatherer groups, suggests that infertile women are vital for successful child-rearing despite being unable to produce children themselves.
The so-called "grandmother hypothesis" originated in the 1950s.
( z1 originate :ARG1 ( z2 thing :name ( z3 name :op "Grandmother" :op "Hypessive" :op "Theory" ) :mod ( z4 so-called ) ) :ARG2 ( z5 date-entity :decade 1950 ) )