If you suspect your dog has brought you human remains, even a tiny chance, please do the responsible thing and call your local police department (not the emergency line, I mean the office number) and explain to them that it is not an emergency, your dog brought some bones home, and you suspect they might be human remains.
The police will collect and check them and it could help solve a case if its actually human remains. If they're not human, which is most likely, they will probably either tell you right away (since they typically are very familiar with human bones, sadly) or they will call you back explaining they're not human and to remember what they look like so their time is not wasted with every bone your dog brings home.