Complete the summary with one tho three words in each gap We took a saw, and we nicked just the edge of it, and there was this really interesting smell that comes from it. It smelled kind of like singed flesh. It was a smell that Natalia recognized from cutting up skulls in her gross anatomy lab: collagen. Collagen is what gives structure to our bones. And usually, after so many years, it breaks down. But in this case, the Arctic had acted like a natural freezer and preserved it. Then a year or two later, Natalia was at a conference in Bristol, and she saw that a colleague of hers named Mike Buckley was demoing this new process that he called "collagen fingerprinting." It turns out that different species have slightly different structures of collagen, so if you get a collagen profile of an unknown bone, you can compare it to those of known species, and, who knows, maybe you get a match. When they cut a piece off one fragment, they..........collagen, which is a substance found in bones and which.............in the ice.