Disappearance of the Neanderthal?

What happened to this descendant of homo-erectus?
1. Neanderthals evolved to a separate species which became extinct and were replaced by early modern humans traveling from Africa.
2. Neanderthals was a contemporary subspecies which incidentally bred with Homo sapiens and disappeared through absorption.
3. Neanderthals never split from Homo sapiens and most of their populations transformed into anatomically modern humans between 50-30 thousand years ago.

I have not done alot of research on this topic but it interests me. So I want to know what you think?