There’s nothing about just one sample, taken from one individual, of mtDNA, that could possibly reveal anything about whether Neandertal and so-called modern humans mated.
Molecular analysis of Neanderthal DNA from the northern Caucasus
http://cogweb.ucla.edu/Abstracts/Goodwin_00.html
“The expansion of premodern humans into western and eastern Europe 40,000 years before the present led to the eventual replacement of the Neanderthals by modern humans 28,000 years ago. Here we report the second mitochondrial DNA (mtDNA) analysis of a Neanderthal, and the first such analysis on clearly dated Neanderthal remains. The specimen is from one of the eastern-most Neanderthal populations, recovered from Mezmaiskaya Cave in the northern Caucasus. Radiocarbon dating estimated the specimen to be 29,000 years old and therefore from one of the latest living Neanderthals. The sequence shows 3.48% divergence from the Feldhofer Neanderthal. Phylogenetic analysis places the two Neanderthals from the Caucasus and western Germany together in a clade that is distinct from modern humans, suggesting that their mtDNA types have not contributed to the modern human mtDNA pool. Comparison with modern populations provides no evidence for the multiregional hypothesis of modern human evolution.”
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