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.
Women who cannot bear children do not have a role to play in the family.
( z1 play :polarity - :ARG0 ( z2 woman :ARG0-of ( z3 bear :ARG1 ( z4 child ) :ARG1-of ( z5 possible :polarity - ) ) ) :ARG1 ( z6 role ) :location ( z7 family ) )