The recovery of ancient proteins from Paleolithic stone tools: prospects and challenges

Dept. of Anthropology, University of Minnesota, 395 Hubert Humphrey Building, 301 19th Ave. South, Minneapolis, MN 55455

Cut-marks on bones in Paleolithic sites suggest that stone tools regularly came into contact with animal tissues during butchery tasks. The archaeological literature from the past two decades contains numerous yet isolated claims of ancient proteins recovered from Paleolithic stone tools. Nevertheless, a systematic and reliable method for analyzing proteins and other organic molecules adsorbed onto stone tools has yet to be developed. The focus of my research on this issue has been two-fold. First, I have been working to develop reflectance infrared microspectroscopy (μFTIR) as a non-destructive and highly precise means of characterizing a wide variety of organic and inorganic residues observable on stone tools. Application of this technique to stone tools from Lusakert Cave in Armenia revealed the presence of proteins and lipids; however, precise identification of these molecules has been hampered by the fact that they appear to be heavily degraded. Second, I have applied matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) to the analysis of proteins adsorbed onto stone tools. Preliminary results indicate that this method can detect large molecules (up to 60 kDa m.w.) on experimental stone tools soaked in protein solutions. However, it was not sensitive enough to detect proteins from these stone tools once they were washed, nor did it yield positive results from artifacts containing suspected organic molecules. Results from both of these studies suggest that the potential for the recovery and identification of proteins from stone tools is great. However, advances in this field will depend upon developing a better understanding of the circumstances favoring the preservation of proteins on stone tools, as well as more precise knowledge of the range of diagenetic modifications that may be encountered in paleoproteins.