Fig 1.
Lusakert Cave 1 (left) and Cave 2 (right). These two caves formed in a basalt cliff along a former meander of the Hrazdan River in central Armenia. Photograph taken by the first author (EF). World orthographic projection shared via Wikimedia Commons with a Creative Commons license.
Fig 2.
Examples of organic residues (dark patches) on LKT1 lithic artifact surfaces. Images by the joint main authors (EF and GM).
Fig 3.
FTIR reflectance spectra for skin flakes.
A μFTIR spectrum of fresh human skin flakes compared to the transmission spectrum for collagen from the reference library of Kimmel Center for Archaeological Science, Weizmann Institute of Science. The spectra have been vertically offset for clarity. We propose the following peak identifications based on our earlier publications (see Monnier et al. [12] for further details): 1. O-H stretching, amide A; 2. amide B; 3. CH3 asymmetric stretching; 4. CH2 asymmetric stretching; 5. CH3 symmetric stretching; 6. CH2 symmetric stretching; 7. C = O stretching; 8. C = C stretching, amide I; 9. amide II; 10–12. CHx bending; 13. amide III; and 14 and 15. C-N, C-O, C-C stretching.
Fig 4.
Four of the twelve LKT1 artifacts examined with μFTIR.
Locations (the red X symbols) on a: G04-1026, b: H05-699, c: H05-477, and d: I05-1051 with the presence of organic residues identified by VLM and SEM. Residues on these artifacts are discussed in the text. Photographs by the first author (EF).
Fig 5.
μFTIR reflectance spectrum for a micro-residue on LKT1 artifact G04-1026 (Fig 4A).
Comparison between a micro-residue μFTIR reflectance spectrum for LKT1 artifact G04-126 (green) and the μFTIR reflectance spectra for fat (red)–see Monnier et al. [12] for peak attributions. These spectra have been vertically offset for clarity.
Fig 6.
μFTIR reflectance spectra for micro-residues on LKT1 artifact H05-699 (Fig 4B).
These spectra have been vertically offset for clarity. We propose the following peak identifications: 3619/3575: probable OH stretching; 3500–2700: complex band possibly reflecting a mixture of carboxylic acids, amino acids and their salts, amides, etc.; 2957: CH3 asymmetric stretching; 2919: CH2 asymmetric; 2854: CH2 symmetric; 2120 and 1950: unknown; 1749/1743: probable C = O stretching (from carboxylic acids, amino acids, etc.); 1700–1530: multiple species, including water OH bending, NH bending, amide I and amide II in proteins, amino acids and amides, C(O)O asymmetric stretching in carboxylic acid salts; 1500–1400: likely CHx bending; and 1259 and 1150: probable C-O, C-N and C-C stretching. The locations of these residues are indicated by the two red X symbols in Fig 4B.
Fig 7.
Artifact residues vs stearamide.
Comparison between LKT1 artifact H05-442 micro-residues μFTIR reflectance spectra (green) and the spectrum for stearamide from the NIST FTIR library (red). These spectra have been vertically offset for clarity.
Fig 8.
Artifact residues vs stearamide.
Comparison between LKT1 artifact F05-891 micro-residues μFTIR reflectance spectra (green) and the spectrum for stearamide from the NIST FTIR library (red). These spectra have been vertically offset for clarity. The peak at 1744 cm-1 might indicate the presence of fatty acids in addition to the stearamide.
Fig 9.
Artifact residues vs stearamide.
Comparison between LKT1 artifact H05-477 micro-residues μFTIR reflectance spectra with the Kramers-Kronig transform applied (green) and the spectrum for stearamide from the NIST FTIR library (red). These spectra have been vertically offset for clarity.
Fig 10.
A thin section of LKT1 Unit 5 sediments.
Viewed in plane polarized light, microphotograph of a sediment thin section from Unit 5 shows an obsidian flake (center) with an adhered residue (as indicated by the red arrow). Micrograph by one of the authors (CM).
Fig 11.
The rockshelter of Crvena Stijena.
The site exists in a cliff that overlooks the Trebišnjica River. Photograph by project members Colin McFadden and Samantha Porter. World orthographic projection shared via Wikimedia Commons with a Creative Commons license.
Fig 12.
Opening an artifact packet in the laboratory.
An example of (a) a sediment packet from Layer M4c2 of Crvena Stijena and (b) the lithic artifact (a proximal retouched Levallois flake) that was randomly selected for residue analysis and placed, unwashed and untouched, on the aluminum foil square.
Fig 13.
(a) A retouched atypical Levallois flake made of brown-grey chert and (d) an unmodified stone from sediment packet M89-9 both exhibit the presence of microscopic organic residues in SEM images (b, c, e, f).
Fig 14.
(a) An unretouched distal fragment of a limestone flake and (d) an unmodified stone from sediment packet P88-216 both exhibit the presence of microscopic organic residues in SEM images (b, c, e, f).