The extent to which we develop either is determined by the interplay of hormones in utero. The human embryo has the capacity to develop either male or female behaviors. Likewise, we humans know masculine or feminine vocalizations when we hear them. The male/female animal didn't learn it from its father/mother. These sex-determined vocalizations are not learned behaviors - they are inborn. You can identify the sex of many animals by their vocalizations. It has a biological basis, just as homosexual attraction does.
