Experimental research at NYU into the working of ivory falsified several naive misconceptions that other researchers and myself had about proboscidean tusks as raw material. My first mistake was to presume that modern African elephant tusk was a suitable experimental analogue for woolly mammoth tusk. Although, superficially, the differences do not appear great, the two forms of ivory exhibit quite different fracture patterns that are the product of significant differences in the angle of intersection of Schreger lines (known as Schreger angles). My observations to this point have been as follows:
- Contrary to our initial presumption, fresh tusks proved extremely difficult to break into, and to reduce to usable parts. Fresh ivory does not fracture along the large scale concentric laminae observable in prepared sections, as we had so naively imagined. Nor can a fresh elephant tusk be sectioned longitudinally by beginning a split at the thin, hollow proximal end (pulp cavity) and propogating it toward the distal end of the tusk.
- Neither Alaskan permafrost ivory collected in the 1920's, nor fresh African elephant ivory could be worked effectively by direct percussion. Attempts at direct percussion produced the same results that one might expect of hitting a stout piece of hardwood with a hammerstone! Indeed, there are distinct similarities in the response of hardwood and ivory to percussion and wedging, based upon similarities in structure and grain. Sizeable flakes were removed by percussion only where the tusk had already been partially split by dessication.
- Neither fresh nor artificially dessicated (kiln-dried) African elephant ivory could be worked by splitting-and-wedging. Upon dessication, elephant ivory developed incipient concentric fractures that conformed to the broad internal laminae of the tusk. However, these were too poorly developed to serve as points of access for wedges. Overheating in a kiln made modern elephant ivory so brittle that it was breakable by hand, and structurally weaker than many 35,000 year-old Aurignacian artifacts.
- At the time we received it, the medial segment of Alaskan permafrost mammoth tusk showed a quite developed concentric fracture at a lamellar boundary near its external surface (Figure 2:III). Attempts to exploit this dessication fracture by percussion-driven wedging from the distal extremity of this medial segment produced broad flakes that hinged outward part way down the segment's length. However, a split could not be propogated through the entire length of the segment, presumably because the lines of force were directed outward when they encountered the interfaces between "superimposed cones" of ivory. With enough labor however, it is certainly possible to scrape, grind and polish such large flakes of fresh ivory into desired forms. Thus, their employment by Aurignacian ivory-workers cannot be entirely excluded.
Fig. 2: Cross-section of mammoth-tusk from the Alaskan permafrost showing I:Slight concentric dessication fractures near the exterior of the tusk, II: The homogeneous inner core of the tusk with nerve canal and radial dessication fracture, III: concentric dessication fracturing cross-cut by radial hairline fractures,IV: Detail of Schreger lines showing how dessication fractures cross-cut the Schreger lines.
- In addition, the slightly dessicated Alaskan permafrost tusk showed radial fractures that cross-cut the concentric laminar fractures (Figure 2:III). While these radial fractures did not provide an effective purchase for percussion-driven wedges to split the tusk longitudinally, this is probably attributable to the extremely "fresh" state of the permafrost tusk. Similar attempts with more highly dessicated lamellar fragments of mammoth tusk led to considerable success in creating long, workable splinters by longitudinal splitting and wedging. In spite of giving the appearance of being "rotten," such subfossil ivory when scraped, ground and polished into beads was indistinguishable from that seen in well-preserved Aurignacian specimens.
- Since splitting-and-wedging constituted a fundamental Aurignacian strategy for working organic materials (Knecht 1993), we conclude that Aurignacian ivory-working techniques are/were not especially appropriate to the structure of fresh or even somewhat dessicated proboscidean tusks. The collection of sub-fossil tusks as raw material has been hypothesized previously by Hahn (1976) for the German Aurignacian, by Phillipov (1977) for the Upper Paleolithic of the Russian Plain, by White (1989a,b) and, most recently, by McLean (1991) for Aurignacian ivory bead manufacture at Abri Blanchard. Although I do not have truly fresh mammoth-ivory at my disposal, the experimental results described above render it highly unlikely that fresh mammoth tusks could have been worked by splitting-and-wedging. We think it nearly certain that, absent some form of artificial drying or purposeful curing of fresh tusks, "sub-fossil" or at least mammoth tusks that were some years old were sought as raw material by Aurignacian ivory workers.
In my experience, there is no archaeological evidence before Sungir for the preparation of whole tusks by softening (heating, boiling), which would have allowed the ivory to have been more easily worked. Even at Sungir however, the operational chain for bead production seems not to have employed thoroughly softened ivory.
Simple soaking of tusks in water has only superficial effects. However, once the tusk is reduced to much thinner fragments, such soaking can penetrate the entire thickness, making drilling, scraping and gouging much easier (an observation first made by Magen O'Farrell). This soaking also works well on subfossil tusk fragments. Comparison of our experimental sample with actual Aurignacian production debris indicates clearly the use of water in the final stages of bead production.
- In my experience with extant archaeological collections, there is no evidence in the Aurignacian for the oft-cited "groove-and-splinter" technique, so common in later periods. While grooving and splintering of fresh tusks is a feasible (if enormously tedious and time-consuming) approach, the splinters that exist in Aurignacian assemblages show no traces of having been incised out of the surface of the tusk. The French sites that have produced the greatest quantities of ivory ornaments and production débris have yielded little in the way of significant tusk segments that might yield insight into Aurignacian approaches to tusk reduction. One possible example is a medial tusk segment said to have been found in the Vallon de Castelmerle in front of several Upper Paleolithic sites, including at least three Aurignacian sites. The segment appears to have been removed from the remainder of the tusk by hacking off both distal and proximal ends, perhaps in preparation for longitudinal splitting. However, the chronological provenience of this piece is entirely open to question.
- Finally, it is worth noting, as has Ritchie (1969:76), that while ivory has properties (color, luster, softness or warmth of touch) that set it apart from such media as bone and antler, these qualities can only be realized by means of polishing with fine abrasives. According to Ritchie (1969:79), modern ivory workers prefer fine metallic abrasives including jeweller's rouge, which is nothing more than hematite/red ochre. Indeed, my SEM analysis of Aurignacian ivory beads revealed particles of red ochre embedded in the fine polishing striae on their surfaces. Moreover, large caches of red ochre have been recovered from two of the richest ivory-bearing Aurignacian sites in SW France: Abri Blanchard and Abri Castanet.
Laboratory experiments using Aurignacian blades of Bergerac flint, a fine limestone grinding stone, powdered red ocher and liberal applications of water (essential to softening and lubricating the surface of the ivory), produced stigmata similar to those observed on Aurignacian ivory beads. Significantly, while most Aurignacian beads show traces of hematite, few if any of them are profoundly stained. In my experience working permafrost mammoth tusk, indelible staining only occurred when powdered hematite was mixed with fat or oil. The superficial nature of hematite deposits on Aurignacian beads supports the use of water rather than fat as a softening/lubricating agent.