[smokingfrog]

How do they know it’s a human bone, if it is a fragment they can’t event determine what kind of bone it is?

[SunkenCiv]

That's why it's best left up to people who have training, education, and experience:

Being studied are some 300 pieces of human bone, as well as animal bones, found in the cave. One piece was identified as being from a wild boar.

[MD Expat in PA]

How do they know it’s a human bone, if it is a fragment they can’t event determine what kind of bone it is?

They do science, and not unlike what forensic scientists (the real CSI folks) do to determine that bone fragments are human remains not something like chicken bones thrown out in the trash.