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.
Grandmothers like to bake cookies.
( z1 like :ARG0 ( z2 person :ARG0-of ( z3 have-rel-role :ARG2 ( z4 grandmother ) ) ) :ARG1 ( z5 bake :ARG0 z2 :ARG1 ( z6 cookie ) ) )