Do you like puzzles?

by Elizabeth M. Scott, Natural History and Archaeology Preparator at the Indiana State Museum

When archaeologists and paleontologists excavate bones, sometimes they are found in several pieces or are so fragile that they break into pieces during excavation or processing. So, how are these finds identified, tracked and pieced back together? Why bother to mend bones back together? What do we learn from this process? It’s a giant 3-D puzzle!

Let’s follow a group of bones from the Bothwell mastodont site, a site in northern Indiana that yielded material representing seven individual mastodonts.

Pieces of jaw oriented and laid out prior to mending.

Paleontologists in the field found a group of bones. The characteristics of the bones and the presence of teeth led scientists to identify this clustering to be a jaw. They gave this grouping of bones a field identification number and marked its location on the excavation’s site map. Back at the museum, the material was washed, dried, catalogued and consolidated (saturated with a resin for preservation). After this, the preparator —me! — began the process of mending the material back together.

Many things can make it difficult to piece a bone back together. Material can be damaged or lost at the time of the animal’s death; or as the carcass deteriorates, pieces may be moved during a site’s development over time; damage can happen during excavation or laboratory processing. Also, non-fossilized bone material acts similar to wood in that it can warp and distort as it takes in and gives off moisture. This can dramatically affect the bone’s shape and preservation during a site’s formation, excavation and laboratory processing.

During the mending process, there are several ways to deal with distortion and lost or damaged fragments. The piece may be placed at an angle during mending, and there’s the addition of fill material to replace missing pieces and to strengthen weak areas. This takes a complementary blending of biology knowledge and art skill.

This fully mended jaw contains 80 pieces.

But why bother with mending these bone fragments? Well, mending bone fragments is important for several reasons. First, it can assist in better specimen identification. One group of small fragments originally listed simply as “vertebra?” can now more accurately be identified as “third or fourth cervical vertebra.” Second, it can reveal better biological information. Only after mending was it possible to determine that one of the five jaws recovered from the site was from a fully mature older adult. Third, it means fewer fragments to track in storage. The jaw in our example is now one large item and not 80 individual ones. Finally, it can give us clues about site formation processes and the relationships between different bones and individuals found across the site. The jaw in our example was constructed of fragments from two different areas of the site.

Check out this video from the Bothwell site.

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