> I could imagine that you can't have 2 genders of the same species that are completely different. This is called sexual dimorfism and is not a rare event. Rea

> I could imagine that you can't have 2 genders of the same species that are completely different. This is called sexual dimorfism and is not a rare event. Really extreme examples appear in some deep sea fishes in the order Lophiiformes I mammals is not so extreme, but it occurs also. Both genders having a different size is common and is what we would find in giraffes if the neck were developped just for fighting.