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"grandmother hypothesis", is based on studies of prehistoric African hunter-gatherer groups.
( z1 base :ARG1 ( z2 thing :ARG1-of ( z3 hypothesize ) :mod ( z4 person :ARG0-of ( z5 have-rel-role :ARG2 ( z6 grandmother ) ) ) ) :ARG2 ( z7 study :ARG1 ( z8 group :mod ( z9 hunter-gatherer ) :mod ( z10 continent :name ( z11 name :op "Africa" ) ) :mod ( z12 prehistoric ) ) ) )