Bourgeon and her colleagues examined the specimens systematically, cataloguing each piece, assessing its condition and surface preservation, and examining modified specimens under magnification using scanning electron microscopy and optical microscopy to characterize the marks in detail.

The process was painstaking.

Not all specimens had surfaces that were well enough preserved to allow reliable interpretation of the marks.

Many bones showed damage that was ambiguous — modifications that could have been produced by stone tools or by natural processes, where the preserved detail was insufficient to make a confident determination.

The researchers were explicit in categorizing specimens into different confidence levels: those where the modifications were confidently attributable to human activity, those where the attribution was probable but less certain, and those where the modifications were ambiguous.

Of the thousands of specimens in the collection, 15 were identified as showing modifications confidently attributable to human activity.