7. Discussion
7.1 One, no one and one hundred thousand types: Keilmesser in Sesselfelsgrotte G-complexes
The first topic discussed here is the definition of the Keilmesser tool-type according to a techno-functional approach. Despite a proclaimed standardization of these tools [18,23], their undoubted variability in shape led to the creation of several sub-types, which, at times, were interpreted differently, ranging from different chronological and geographical groups [12,50,105,106] to subsequent stages of reshaping and modification [20,23,61] and to distinct functional and/or aesthetical reasons [9,18,23,66,107]. Regarding the last hypothesis, bibliographical use-wear data concerning the Keilmesser from Sesselfelsgrotte confirm, despite the widely accepted notion of a function as hand-held knives, the presence of hafted pieces. In addition, there are examples for functions other than that of a knife: one item was identified as a scraper/rabot, and a second one is a hafted projectile [67].
The results of the analysis of the 3D morphological variability confirm a certain variability within Keilmesser, even if more limited than in the other tool-types. Our research protocol tried to overcome their classic typological division, which is mainly based on the outline, by elucidating their functional history. The cross-check of the identified techno-functional schemes by data on variability resulted in the consistency of three main sub-types (also corroborated by the group distances in the 3D morphology (Fig 15a):
One group defined by the actual or past presence of a distal point (schemes 1, 2 and 2b), which represents the majority of the investigated items (n = 38, or 65.6%)
One group defined by the presence of a curved, convex or segmented back (schemes 6 and 6b), comprising 14 tools (24.1%).
One group with a heavily curved cutting edge and the absence of a pointed end (schemes 6/7 and 7), comprising 5 tools or 8.6%.
Fig 15. Variability between Keilmesser techno-functional schemes showed by group distance (a), length (b) and medium angle (c).
A clear dimensional gap can be noticed between these groups, with the pointed-tools being larger in size. Among these, scheme 2 is associated to larger tools and narrower cutting edge angles (Fig 15b and 15c). If we accept the reduction-stage interpretation, this data would hypothetically set scheme 2 as the main initial scheme of Keilmesser tool-type. In this sense, Keilmesser of scheme 2 could be modified by resharpening to scheme 2b in cases when the tip reshaped into a rounded outline (after it became blunt). Alternatively, Keilmesser of scheme 2 could also be resharpened at times into scheme 1 through the gradual backward reshaperning of the cutting edge and the removal of the bow, following already known reduction processes [20]. However, scheme 1 Keilmesser could also represent an initial TFS for tools manufactured on chert plaquettes. In the more advanced stages of reduction, the tip could completely disappears and, based on the initial shape of the blank, schemes 7 or 6/7 and 6 or 6b can be achieved; this may apply especially to the latter, since these are generally smaller tools with wider cutting edge angles (Fig 16). Within each group, there was an increase of the active angles with the decrease in the blank sizes, thus associated to the reshaping of the tool (Fig 17). However, even in the group characterized by a convex back, the bigger tools (already quite small) have narrower angles, suggesting a direct manufacturing that hasn’t undergone many resharpening phases. Alternatively, if the resharpening was present, it probably had little influence on angles and therefore on the techno-functional scheme. Therefore, schemes 6 and 6b could also represent Keilmesser variants adapted to small-size blanks and plaquettes made on Jurahornstein and particularly on small Radiolarite and Lydite pebbles, characterized by segmented and strongly convex natural edges (Fig 18). A certain correlation between tool shape, raw material type and dimensions could imply functional and ergonomic reasons: the smaller tools generally need a curved back to facilitate the manual handling [75]. Conversely, pointed Keilmesser are manufactured on a wider variety of blanks and raw materials, including Cretaceous Cherts and quartzites, which are thicker and heavier, allowing for the power needed by a larger cutting tool provided of a perforating point.
Fig 16. Hypothetical diagram proposed for the manufacturing of the different techno-functional schemes typical of Keilmesser.
The nature of raw blank and their progressive modification through reduction and reshaping could have been the main reasons of this differentiation.
Fig 17. Distribution of the cutting edge angle of keimessers’ groups according to the blank length.
Fig 18. 3D scans of Keilmesser manufactured on lydite or radiolarite pebbles showing the exploitation of the natural convex surfaces for the conception and the obtaining of the back.
It is therefore possible that at the base of the Keilmesser diversification there are different techno-functional, handling and use-related schemes partially adapted to raw materials and blanks, but also technical consequences like the changing and evolving of schemes according to reuse and reshaping. If we apply a basic working-step analysis recomposing the (last) phases of production and modification of the tools, three technological groups are evident: core-tools (kerngeräte), blank-tools and exhausted tools. If we consider the Keilmesser techno-funnctional schemes, that grouping can reflect a direct requirement (both functional and/or ergonomical) as well as a consequence of tools’ reduction; the grouping in technological groups, on the contrary, necessarily reflects a need in terms of technological versatility or strategic/economic potentiality, which indirectly affects the object and its morphometry.
In this sense, the blank-tools are pieces where the technical investment seems to be aimed exclusively at the first shaping of the tool from the selected plaquette, the subsequent achieving of a bifacial cutting edge (mostly plano-convex) opposed to a back, and the possible resharpening stages; each identified working stage regards the first manufacturing or the rejuvenation of the tool (Fig 19).
Fig 19. Keilmesser blank-tools, that is the blanks shaped with the only function of manufacturing an asymmetrical backed bifacial tool.
In green, the detachments aimed to first tool shaping; in red, edge refining. From the top left: S2221/68; S1525/68; P1559/S64; S310/74.
Conversely, core-tools are implements which also had a probable function as “matrix”, source of raw material for producing smaller usable flakes. This ramified sequence has been recognized on 22 out of 58 blanks, with the exploitation mainly noticeable on the lower flatter surface but occasionally even on the upper one. According to the bifacial plano-convex volumetric concept defined by Boeda [53], a flat surface is produced in order to achieve the plano-convex active bevel; in this first stage, flat, wide and deep flakes are detached mainly from the cutting edge and, in several cases, from all over the periphery in a nearly-centripetal surface exploitation pattern, which can also be aimed at the production of functional flakes (Fig 20). Wide and flat detachments are also related to Keilmesser reshaping phases in order to maintain the angle of the cutting edge [61], according to a method applied also to much older bifacial tools [108]. However, an additional techno-economic objective has been recognized on these tools through the work-step analysis. For example, artefact P1963 records a first preparation of the plano-convex cutting edge, followed by a mainly upper reshaping that gradually erases the lower negatives. Flakes are then detached on the lower surface from the back that is used as a prepared striking platform. A certain irregularity in the back thickness suggests that the main goal was the production of flakes also 3 x 2 cm in size (Fig 20a). In artefact P5596, the working and faceting of the back from the lower surface is evident: the preparation of the striking platform and the surface exploitation resemble the Levallois concept (Fig 20c). Artefact P5791 however, records a core-like exploitation that exhausts the blank by removing most of the back, which also has the function of a striking platform (Fig 20b). In these and several other examples, the exploitation is bipolar to centripetal, and the Levallois-like conception is emphasized by the detachments parallel to the blank secant plane, the knapping angles around 90 degrees and the accurate preparation of the peripheral frame in correspondence to the blank’s back [73]. This working can be applied, in some cases, also to the opposed surface thanks to the double plano-convex volumetric conception of the Keilmesser-tool [53]. The obtained products are oval or elongated small to medium sized flakes, suitable for immediate and short-term precision activities framed in situations of compelling needs and a shortage of raw materials. Keilmesser are generally known to be “core-tools”; their volumetric concept is well defined in the “fourth type of bifacial volumetry” based on Kůlna cave tool [53]. Their productive potentiality, derived from the ramification of their surface-exploitation, has been particularly investigated in the Crimean Micoquian; here, the production of usable flakes obtained from surface shaping of bifacial tools is assumed in their first shaping, in the re-tooling process and also after the discharge of exhausted tools through a recycling of the blank [109,110]. Within Central European Keilmessergruppen/M.M.O., this practice is rarely reported: some small and worn pradniks from Buhlen have been recognized as recycled cores after an abandonment as tools, but there is no mention of a possible alternation between the two functions [20]. Core tools have been also recognized in Neumark-Nord 2 and Königsaue [111].
Fig 20. Diacritic schemes of Keilmesser core-blanks showing the patterns of reduction and exploitation of the lower surface and, occasionally, the preparation of the back, used as striking platform.
The red and blue detachments may represent those aimed at creating usable blanks, while the yellow and green ones at managing the lateral convexities and regularizing the surface. From the top left: P1963/S64; P5791/S65; P5596/S65; P1922/S64; S3887/69.
Finally, exhausted tools correspond to the extremely reduced blanks, where most of the working stages are no longer visible except the last ones, until the complete exhaustion of the usable volume. Very often these tools are made out of non-local raw materials, but possibly characterized from the beginning by smaller raw blanks, better suitable to some kinds of shaping (like schemes 6 and 6b) (Fig 18). These artefacts are often present in assemblages of the Keilmessergruppen/M.M.O. context: already recognized and defined “small pradnik knives” or exploited specimens by Krukowski [60], with the reshaping phases they may reach a reorientation of the blank, which at the end, often assumes a triangular shape.
Within the investigated assemblages from the G-complexes, those belonging to the first stages (layers G2 to G5) show high frequencies of core-tools, and every scheme is represented, indicating thus the requested versatility of these tools in these phases (Table 11). Exhausted tools show an increase in layer G2 and prevail in layer G1, where the longer tool use-life is probably linked to high requirement of raw material and mobility. Meanwhile, few core-tools suggest a lesser need to versatile and multi-purpose Keilmesser in the last layer. If we cross data with Richter’s inventories indicative of occupation cycles [9], we note a difference between initial and consecutive inventories mostly in the amount of blank-tools, which are three times more frequent in the latter (Table 12). This direct and more exclusive use of the Keilmesser tools attests more functional specialization, which goes well along with the assumed more stable occupation as base camp with logistic mobility recognized in the consecutive assemblages [28,68,85]. The selection of the best raw material [9] for blank-tools may also indicate a certain degree of planning aimed at achieving a greater tool-set effectiveness.
7.2 Differentiation and imitation: Backed artefacts within Keilmessergruppen
If the Keilmesser’s internal variability can be related to the reasons discussed above, what is considered Keilmesser or not is an equally intricate issue. The limits of a sharp typological definition are clear, since Keilmesser often overlap with the other types, both in shapes and morpho-functional features. The identified TFS are differently represented within the tool types, but theoretically every backed tool scheme can be fulfilled through the use of non-retouched or retouched flakes, unifacial scrapers or bifacial knives.
This is also true in our case study, where no exclusive schemes for Keilmesser exist, although there are some clear preferences. This data is confirmed by the 3D morphology, where the overlap between types in the PCA representation is evident (Fig 13a). If we investigate and compare the back of these tool types, we can notice a generic difference in its conception even if its dependence from the initial blank is equally important. Jurassic chert plaquettes with natural thick parts are usually shaped into Keilmesser, a behavior that implies wider reasons of raw material management, but they are also used for other bifacial tools and scrapers. Paradoxically, the raw material doesn’t seem to considerably affect the final form, since the artefacts produced in the most utilized Jurassic chert (Ju01) are more similar to the ones produced in Cretaceous cherts and quartzites (Kr) instead of other varieties of Jurassic cherts (Ju10) (Fig 21a). A typological preference related to the raw material supply can be noticed. Among Keilmesser, a number of radiolarite-lydite specimens are present, while among other bifacial tools they are missing. These are mostly exhausted tools deriving from a long use-life or manufactured on smaller blanks collected in fluvial gravels, probably utilized in periods of scarcity and “emergency situations”. A number of scrapers are also made out of red radiolarites, while lydite scrapers are rare. The radiolarites, outcropping in the alps, were exclusively collected in semi-local Danube gravels, while the lydite outcrops in north-eastern Bavaria and was probably collected further afield, since secondary outcrops are also located downstream from the site. This is why mobility strategies, related to the tools’ reduction concept and type of occupation, may have led to a choice in the raw material management [9].
Fig 21. On the left, group distance for raw material showing differences between the different varieties of Jurahornstein; on the right, distribution of the cutting edge angles according to the weigth diminution (“Ju”, “Ju01” and “Ju10”: Jurahornstein; “Kr”: Cretaceous chert and quartzite; “Ra”: Radiolarite; “Ly”: Lydite).
The comparison of the tools’ cutting edge, instead, provides the most interesting element, if related to their functional implications. The cutting edge angles and bevel are indirect indicators of functionality, penetrative potential and movement of use [93,99,112]. A strong consistency is noticed when comparing the angles formed by the upper and lower surfaces on the cutting edge of Keilmesser and scrapers. Simple backed flakes bear more acute angles; however, the first two types result from resharpening and retouching phases that could have modified and increased the angle. If the data regarding angles are crossed to the Keilmesser’s weight, empirical index of their reduction degree, a sharp increase of the angles in the lighter exhausted tools can be noticed (Fig 21b). Scrapers, whose angles are always very similar to the Keilmesser, were found to have only a slight increase of angles, which can be related to the fewer influence of retouching respect to their volume. On the contrary, flakes don’t record any increase but the opposite: since flakes were not furtherly reduced, we can assert that small backed flakes were manufactured with a narrower active angle probably for their high functionality for precision and fine activities, as demonstrated within Discoid assemblages [75]. For this reason, we found that weight could represent a measure of reduction if applied to heavily reduced Keilmesser tools, but in the case of flake blanks it is more likely to represent the initial blank size.
The cutting edge bevels show a recurrent asymmetry between the lower and upper profile. The more concave lower bevel of Keilmesser essentially derives from the need to detach flakes in order to create a cutting edge in a raw blank. It thus represents the concavity of the flakes’ negative; apart from this feature, the lower bevel is mostly flat in Keilmesser as well as in other tools. Concerning the intersection between upper surface and cutting edge, Keilmesser record a convex or slightly convex profile that is halfway between backed flakes and backed scrapers. This data fits well with the presumed functionality of Keilmesser [9,67,113], since extremely convex and asymmetric bevel related to angles > 60° seem to be the prerogatives of scraping tools, while more flat, symmetrical or slightly asymmetrical bevel should be predisposed for cutting related to longitudinal motion [93,95,99,114,115]. However, it is evident also in this case that a quite internal variability is recognized in each tool type, and the morpho-techno-functional features of the Keilmesser overlap in most cases with those of scrapers and, in lesser extent, of simple flakes. In this regard, the available use-wear data on G-complex tools states that hafted or hand-held knives are documented among bifacials, Keilmesser, and unifacial Mousterian tools, within quite different typologies of artefacts and among not retouched pieces [67]. The “tool-type” is thus never associated to a single use or specific function, nor the opposite, confirming in a preliminar way what has been assumed by the techno-functional approach.
In this sense, typology turns out to be fluid, relying on isolated features. The major discriminating factor between Keilmesser and other backed artefacts is thus the bifacial retouch, combined with their volumetric concept which allows a greater potential for reuse [53]. However, with regards to this factor, Krukowski [60] already focused his attention on scrapers related to prodniks as unifacial transitional forms. Also Jöris [23] states that not all Keilmesser are of the core-tools type but they can also be manufactured on flakes, including a unifacial variant resembling backed scrapers and therefore transitional. Similarities in this regard between Keilmesser and scrapers in their shaping biograhies have also been noticed in other Keilmessergruppen//M.M.O. assemblages [19,62]. These transitional forms however, possess low variability that is related to the limits of the flake blank, implying medium or low resharpening potential and excluding any other multi-functional ambitions or their exploitation as cores. In fact, the resulting tool is a simple or scaled scraper with Keilmesser-like morphology but differing from it for other elements; a sort of simplistic version of Keilmesser, since many morpho-technical requirements (plano-convex bevel, technical back) are already fulfilled by the flake blank [62]. Scrapers bearing traces of tranchet blow technique (pradnik scrapers [66]) are also considered smaller and shorter-lived versions of Keilmesser, besides being sometimes associated to less experienced knappers or children manufacturing [116].
Conversely, classical Keilmesser are bifacially retouched blanks with a very high reuse potential. Classical Keilmesser are generally long-lived, mobile and multipurpose tools, according to working-step analyses of several KM-bearing assemblages ([9,19,52,66]. The final shape is, as already seen and confirmed by our dataset, a consequence of numerous subsequent stages [20,23,61]. These stages can lead to the tools’ reshaping or "remolding", a recycling that involves a different function [117]. In Moravski Krumlov IV is also hypothesized that, in Szeletian, Streletskayan and perhaps also Micoquian assemblage, Keilmesser-like forms can constitute itself a phase in the manufacture of unfinished leaf points [109,118].
In any case, it is significant that a large part of Keilmesser from Sesselfelsgrotte had elaborate biographies that included different functions and objectives, from the “simple” tool to the matrix for the production of small-medium size flakes. Moreover, these phases could have been both subsequent and alternating (Fig 20). The G-complexes assemblages are also known for the presence of a microlithic tools component, mainly round scrapers or raclettes manufactured on small flakes (Fig 22a) [9,119]. These flakes were mainly obtained from surface shaping and exploitation of chert plaquettes, the same blank for most of Keilmesser; there is thus the possibility that the two reduction sequences are intertwined (Fig 22b). After all, in the inventories where microlithic tools are numerous (A01, A06, A08, A09), the core-tools Keilmesser are very well attested; where they were less in number, core-tools are also absent or isolated. In the absence of refittings, techno-economic and functional data highlight the manufacturing of these tools out from the site and their very specific function specialized on working of vegetal materials [9,87]. This is why they go well with a possible obtaining from different stages of Keilmesser shaping, as the opening of chert plaquettes on lower surfaces or the mainteinance and reshaping stages, where the production of different flakes morphologies (round, ovalar or laminar) is attested [9].
Fig 22. Microlithic tools component recognized in the G-Complexes (a); flakes produced from the initialization and shaping of Keilmesser (b).
Modified from Richter 1997.
The use of flakes obtained from bifacial tool shaping is attested in assemblages from all over the European Middle Paleolithic, from already mentioned Crimean Micoquian [110,120] to the Mousterian of Acheulean Tradition in South-Western France [48]. Keilmesser are the perfect tool adaptable to this bifacial multi-purpose conception, thanks to the easiness in which functional operational schemes can be modified through tool rotations and base-point or surface inversions in the volumetric exploitation [63]. The versatility of Keilmesser scheme allows the implement to be reorganized by extending its use-life and reshaping stages. Moreover, the double and alterned plano-convex concept allows both tool and core objectives to be met.
To sum up, the mental template behind the production of unifacial or bifacial backed tools is quite similar if not the same. The objective are cutting and/or scraping tools characterized by at least three asymmetries [20]: a longitudinal one (base vs tip, when present), a transversal one (back vs cutting edge), and the third on the cutting edge (flat vs convex) (Fig 23). This scheme may include most Keilmesser, many scrapers and some backed flakes. However, their maintenance and potential uses are different.
Fig 23. The three main asymmetries of Keilmesser are showed: base/point, back/cutting edge and, viewed in cross-section, flat/convex surfaces.
Therefore, we propose that at the base of this division there might be a sort of imitation process of bifacial backed knives towards the simple backed artefacts on flake. Boëda also pointed out that from a morphological point of view the edge of a plano-convex bifacial tool and of a modified knapping product are equivalent [53]. It has also been said that both unifacial and bifacial tools cover the same intentional sphere, despite having their own specific techno-functional features [19]. Moreover, 2D morphometrical Elliptic Fourier Analyses has shown that their reduction, in keilmessergruppen/M.M.O. assemblages, often follows quite similar trajectories [61]. This is also true for the bifacial tools with flat retouch; common types in late Middle Paleolithic assemblages, whose biographies have been related to simple unifacial artefacts [12,121,122].
If it has been said that unifacial backed knives are the simplified version of bifacial backed knives [62], we could assert that bifacial backed knives are the strategic, versatile versions of their unifacial counterparts. This “economic” interpretation enhances the tool as an exploitable volume, as a multi-purpose and multi-functional blank, as well as its possibility of angle maintenance [61], through intertwined and common working stages.
After all, the structure of the bifacial knife itself, independently from the context, has been related to products made in order to be rejuvenated [61,108]. In Bavarian Keilmessergruppe/M.M.O. contexts, the frequency of some types of bifacially shaped tools and leaf points has been interpreted as strictly dependent on the mobility strategies of the human groups that made them. Their frequency can be higher in palimpsests of recurrently visited, specialized leafpoint sites, where single pieces were used and abandoned after multiple import (like Weinberghohle, Zone 4 or Zeitlarn 1). They can be equally abundant, but with a larger variability of different forms, at residential sites with long times of activity [52]. The underlying idea is that the longer a site is used in the course of the same occupation, and the more logistical the land-use pattern is, the more often long-life objects of otherwise mobile toolkits reach the very end of their use life at the same site. This scenario is based on the assumption that bifacial tools are used regularly and independent from the respective site function. Instead, the increased amount of discarded items is simply a consequence of staying at a camp site longer than the use-life of the single tools, irrespective of if they have been manufactured and used on-site or imported. Their effectiveness as long-life tools has been experimentally tested, with an estimate duration of at least several weeks [20]. The idea that parts of the Micoquian package, including Keilmesser, are more often discarded at base camps with long-term occupations therefore does not necessarily contradict to the well-proven notion that Keilmesser have a high strategic and versatile value and are part of a mobile tool-kit. Because it depends on the overall land use pattern, which is in general seen as being flexible, it does also fit to the high frequencies of Keilmesser observed at short-term and specialized sites like Lichtenberg or Zwolen.
Keilmesser, however, are not the only strategic tool-type in the European Late Middle Paleolithic, other tools imply similar duration and multi-purpose potential, like limaces. This tool involves an anticipatory behavior and, by integrating multiple functions, constitutes an original way of raw material circulation on long distances [123]. Limaces have sometimes been confused with Kartstein-type points, which are also characterized by upper invasive retouching, dorsal keel, plano-convex section and, moreover, flat detachments in the lower surface when the blank wasn’t naturally provided. These two types are overlapping [124] and the similarities with Keilmesser-concept concerning the potential for resharpening is evident, besides the common presence in several sites [12]. Therefore, in contemporary contexts characterized by high and strategic mobility there were possibly different traditions in order to manufacture long-term tools potentially similar, but techno-functionally different: besides Keilmesser there were limaces, Quina scrapers, and possibly other bifacially-shaped tools [48,125].
We can therefore assert that backed unifacial and bifacial tools can derive from the same operational techno-functional concept. Their differentiation is instead an ecological consequence implying a specific requirement that is having a versatile volume that can be exploited for different purposes. This tendency is noticeable in several transitional bifacial forms (like bifacial scrapers or limaces), and finally in leaf points or leaf-knives, which in turn could have been a further consequence of reduction of bifacially shaped core-tools with or without a back [118,126]. However, this ecological variant doesn’t deny the possible design of a specific mental template for Keilmesser that, like other potentially similar tool-types characteristics of other techno-complexes, may have assumed a strong cultural value, perhaps in a late phase of Keilmessergruppen/M.M.O. complex.