To be more precise, there are actually only a few known bone fragments of Denisovans, so details about their morphology is not known. You can tell that they’re

To be more precise, there are actually only a few known bone fragments of Denisovans, so details about their morphology is not known. You can tell that they’re different species by analyzing the DNA to figure out when the lineage diverged from a common ancestor with Neanderthals. In the case of Denisovans and Neanderthals, if I recall correctly, they diverged like 400k years before the specimens which have been found were alive. Whether that qualifies as a different species depends on how you define species. But the divergence is similar in scale to the divergence between humans and Neanderthals, so if you consider humans and Neanderthals different species, then Denisovans are also a separate species. The alternative is to consider then all different varieties of human. Edit: just wanted to add this write up by Razib Khan for anybody interested: https://www.gnxp.com/WordPress/2018/08/22/hominins-are-still-having-sex-caught-in-flagrante-delicto/ https://www.gnxp.com/WordPress/2018/08/22/hominins-are-still...