Grandmothers are a bit of a mystery, biologically speaking. If the biological purpose of life is to survive and have children, why are they so important even once they've stopped being able to reproduce? Of course, as we all know, grandma's are the rock of most families, and it turns out, biologically also incredibly useful. Grandmothers are a logical necessity, your mother and father also had mothers so that equals two grandmas for you. But the evolutionary role they play in many of our lives has been less easily explained until now. Why are they so helpful? Why do they stop having children of their own? Why do we have grandmothers?!Ella speaks to anthropologist Dr Emily Emmott, and midwife, educator and grandmother Sheena Byrom OBE BBC Studios Audio Production Producer Emily Bird Additional production Olivia Jani Series Producer Geraldine Fitzgerald Executive Producer Alexandra Feachem