The same way a good CSI can tell a human bone from animals at a crime scene. Certain bones and bone structures have only been found in humans, there direct ancestors and some off shoots. Certain other bones and bone structures are only found in modern Homo sapiens, now these can and have been misidentified, but the scientists involved try very hard to prove what they say before they report it because nobody in the scientific world wants to be found a fool. If these are not in fact what this scientist claims them to be and some other scientist proves it then the original scientist would lose funding and respectability along with all his other published works coming under more intense scrutiny.
Look at those bone fragments again. While I agree that they can identify human remains given enough to work with, it seems incrediable that they can make such claims with the paltry bits in the photo which accompanied the article.