Scientists Extract Human and Deer DNA from Paleolithic Pendant Found in Denisova Cave.

Research like this is possible because Russia has nothing like the NAGPRA law. If NAGPRA existed there, it would require "returning" ancient human bones and artifacts to someone or other, and we would not have had the chance to learn from them about the evolution of our species -- for instance, we would not know that nearly all of us humans have Neanderthals among our ancestors.

As for the Denisovans, another strain of humans also known from things found in Denisova cave, we wouldn't know they existed at all.