Measuring Wear in Bone Tools

A UC Davis anthropologist has been building a catalog of high-resolution 3D models of bone tools worn by working various materials, all in the name of archaeology.

UC Davis graduate student Naomi Martisius with a rib bone she has shaped as a leather-working tool. Bone tools like these are often found in archaeological sites with the tips broken off.

Humans have been using bone tools for about two million years, and by about 100 thousand years ago were processing bones to make tools for specific purposes, such as working animal skins into leather. Both the way tools are made, and the way they are used, leave tiny marks on the bones that could give information about how these tools were prepared and used.

Naomi Martisius, graduate student in anthropology at UC Davis, has been studying bone tools made by Neanderthals. Previously, analysis of the marks on these tools has been something of an art of interpretation. To remedy this, Martisius and her coauthors at UC Davis and in France and Germany set up an experiment to reproduce patterns of manufacture and wear on bone tools so that archaeologists can make a quantitative assessment of how they were made and used.

“We want to understand how bone changes when you work it,” Martisius said. This is a crucial first step to understanding Neanderthal and human behavior, she said.

Martisius took pieces of cattle rib bone and either shaped them with sandstone or flint – methods used by Neanderthals and Homo sapiens– or left them unprocessed.

How bone changes with wear

Then she mounted the bone tools in foam on a laboratory rocking device, so that they could be rubbed against fresh animal skin, leather or bark, simulating prolonged use.

Martisius used dental putty to make impressions of the bone surface at the start and throughout the process and used a confocal microscope to capture three-dimensional scans of the surfaces. These were analyzed with software usually used by mechanical engineers to measure wear on machine parts.

The scans reveal tiny pits, holes and striations that appear and sometimes disappear as bones are worn down. Bone is a very variable material, Martisius noted.

As bone tools wear, microscopic pits and scratches appear on the surface. (Naomi Martisius/PLOS One)

Duration of use turned out to have the largest effect on bone surfaces, with fresh animal skins being the most abrasive. More significantly, the results will help archaeologists get a better idea of how tools were made and used.

“We hope that this data will be a reference for studying archaeological remains in the future,” Martisius said.

Coauthors on the study, published Nov. 7 in the journal PLOS One, are: Teresa Steele and Mark Grote, UC Davis; Isabelle Sidéra, Centre National de la Recherche Scientifique, Université Paris Ouest Nanterre, France; Shannon McPherron and Ellen Schulz-Kornas, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.

More information

Time wears on: Assessing how bone wears using 3D surface texture analysis (PLOS One)

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