Male + Deep Voice = + Woman + Babies

Holy Smokes [squeaky voice]!!! This is one of the reasons why I love linguistics. Sometimes, linguists can do really cool research, like this : BBC NEWS. Although I think it was actually an anthropologist who conducted the study. Whatever. They could use a linguist anyway. 

Sorry guys with squeaky voices: you would find it hard to have plentiful babies if you lived 200 years ago, and/or in tribal Africa.