You said the DNA means the two are different species. Well back it up with evidence.
Well, I've read a fair amount of literature, and if the two papers Mammuthus abstracted follow the standard procedures, the authors have also published a supplement containing all the original sequence data on which they base their conclusions. All you need to do is compare the sequences yourself and see if they are the same.
If they're not, there's two possibilities: if the sequences differ only a bit, you might be looking at two haplotypes of the same species. However, if there are significant bits that are found in one specimen and not another, you've got evidence that they
may not be the same species. And if you get a number of specimens of each type and the same differences appear each and every time, then your evidence that they're different species is much stronger.
Finally, for your specific point that
neanderthalensis may be simply an early version of some Indo-European, the easy way to make the determination would be to sequence known
sapiens mtDNA from the region and compare it to your putative "ancient Germans". That's pretty much what they did in the second referenced article (although I won't claim any regional affiliation, the
H. s. "type" specimen, including the ones used in the human genome project, is Indo-European). So since there's significant differences in mtDNA (not in the much more variable nuclear DNA, which was not studied AFAIK), with a fair number of specimens, it is a quite reasonable conclusion that the sequences represent different species.
Neaders and us are the same people. Neaders spoke either German celt or Basque etc.
I'd be very interested to know your source for this. Given the various colonization/migration waves that wandered through northern Europe over the ages, determining what someone spoke a long time ago in that region is a bit problematic IMO. Especially since Basque appears to be unrelated to German OR Celt (do you mean Pict?).