I've never heard of a male alto. The only male voice categories I've heard are... Male Soprano | Counter-Tenor | Tenor | Baritone | BassWith Females...Soprano | Mezzo-Soprano or Alto | Contralto or...
Male humans have a different genetic structure from females, consisting of an X and a Y chromosome, where females have two X chromosomes. The genetic difference accounts for various differences...
If you're referring to the alto range, then the really high male opera singers are called counter tenors. They are pretty rare voice types and there are not many operas with counter tenor roles....