It could have been from the mastodon itself — a piece of the animal’s own skeleton that had migrated into the rib through post-mortem processes.

It could have been from a different part of the same individual, broken during death or decomposition and compacted into the rib by sediment pressure.

Or it could have been from a completely different individual — a weapon made from bone, introduced from outside the animal’s body by a deliberate act.

To distinguish between these possibilities, the Waters team applied biomolecular analysis — specifically, protein analysis — to the embedded fragments.

Proteins, like DNA, carry molecular signatures that can distinguish between individuals and between species.