In fact, we have no idea whether they had language or not, and calling them both "stem-humans" emphasizes this. (As I pointed out earlier, we even have no idea whether Neandertals and Denisovans had language, although since they had our variant of the FOXP2 gene, it is tentatively probable.)The divergence between humans and Neandertals is actually much, much less than between the species of Pan.