Interbreeding is why they are no more. Only logical answer.
I still say that is where Down's Syndrome comes from, a throw back of some sort.
Umm, no. Mitochondrial DNA indicates no interbreeding took place. And Down's Syndrome is caused by the presence of an extra copy of chromosome 21, which is caused by nondisjunction in meiosis when the gametes are made. Please, please don't repeat that hurtful and wrong idea again.