Scientists use butchering marks that prehistoric humans left on animal bones to learn more about human evolution. CC0 Creative Commons

Scientists used knives to learn more about human evolution and how smart our prehistoric ancestors were, and now their cuts are getting more precise.

A team of researchers found a way to more accurately analyze marks on animal bones left by humans butchering them, using 3D imaging and statistics. In their study in the Journal of Archaeological Science, the scientists refer to the cuts and slices as “bone surface modifications” and say they are important for understanding prehistoric human behavior. Although archaeologists have tried to identify and study them since the 1800s, the teensy size of these cuts has made it difficult.

“In archaeology, butchery marks on animal bones are a key piece of evidence used to answer questions about food acquisition in prehistoric hunter and gatherer populations,” researcher Erik Otárola-Castillo said in a statement from Purdue University.

The marks, on the remains of sheep, bison or other creatures that were hunted for their meat millennia ago, are tiny: just a few centimeters long and a fraction of a millimeter deep. They can be easily confused with other damage to the skeletons.

But accuracy matters because knife marks can be evidence of human presence in a location during a certain time period, for example, or speak to how advanced their tools were. In this way, the human use of stone tools on animal bones can tell scientists a lot about human evolution.

This new system for distinguishing between cut marks and more natural markings relies on a special kind of microscope that takes 3D measurements of the subject, to show how deep and rough the slashes are on a micrometer and nanometer scale. According to Purdue, the researchers tested their new identification method on bones that were butchered to replicate the marks of prehistoric humans. They found they could correctly separate butchering marks from other damage 88 percent of the time.

“This approach represents a major improvement in accuracy when compared to many archaeological methods, and improving this technique will help us get the human evolution story correct,” Otárola-Castillo said. “By strengthening quantitative methods to evaluate archaeological evidence, we will be able to learn more about early humans much more quickly.”