[dangus]

By definition, if they had fertile offspring, they were one species. In some cases, this indicates that populations that were once thought of separate species are one (Polar Bears and Grizzly bears, for instance.)

In this case, Neanderthals were already regarded as Homo Sapiens, as many humans have significant amount of Neanderthal in them (no joke) meaning that offspring of H Sapiens Sapiens and H Sapiens Neanderthalis were fertile.

I’m not sure what the news is here: “A 2013 comparison with the genome of another Neanderthal from the Denisova cave revealed local interbreeding with local Neanderthal DNA representing 17% of the Denisovan genome, and evidence of interbreeding with an as yet unidentified ancient human lineage.” [Wikipedia citing Pennisis (2003) in Science]

[SunkenCiv]

The Neandertal Enigma
by James Shreeve
in local libraries

"Frayer's own reading of the record reveals a number of overlooked traits that clearly and specifically link the Neandertals to the Cro-Magnons. One such trait is the shape of the opening of the nerve canal in the lower jaw, a spot where dentists often give a pain-blocking injection. In many Neandertal, the upper portion of the opening is covered by a broad bony ridge, a curious feature also carried by a significant number of Cro-Magnons. But none of the alleged 'ancestors of us all' fossils from Africa have it, and it is extremely rare in modern people outside Europe." [pp 126-127]