When we take other similar species (or sub-species) into account, like neanderthals, we see that the difference is in the level of some capabilities like problem solving and memory.
And because of the level of these capabilities, modern humans can be distinguished as an animal which isn't bounded to a specific habitat on Earth.
If one looks to the animal species that live today and want to "distinguish" human, then she/he can think that there's a massive difference between human's and other amimals' communication and problem solving capabilities. But, rather than a difference, we need to look this as a kind of gap which isn't actually exist.
So, if needed, we can distinguish modern humans as a species from others on the basis of the results of their capabilities, not on the basis of the biological properties that cause these results.
Of course, this kind of questioning (trying to distinguish human) doesn't affect biological classification and identification of species at all, but it can affect people's general attitude and opinion on this issue.