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Post by Admin on Aug 7, 2020 5:54:19 GMT
Overall, we anticipate that the regulatory effects of RAs and NDAs differ between tissues based on the genetic diversity and strength of constraint on their regulatory landscapes. Supporting this, nervous system tissues (including the brain) and the testes have extreme levels of selection on gene expression (high and low, respectively) (49). Given the range of RA eQTL enrichments across GTEx tissues, including tissues without evidence of selection against Neanderthal alleles, we propose that the presence of RAs and NDAs is the result of a mixture of selective pressures acting within the regulatory constraints of each tissue. Therefore, RAs likely play a functional role across diverse tissues and thus may contribute to the persistence of introgressed haplotypes. Contrasting the functional effects of RAs and NDAs will be especially useful in understanding how evolution acted on introgressed haplotypes. Although RAs and NDAs co-segregate in Eurasians, they are the products of two distinct evolutionary histories. Previous work has implicated the small effective population size of Neanderthal populations as a key factor in their transmission of weakly deleterious NDAs into AMHs via introgression (19, 20, 50). In contrast, RAs are more evolutionarily conserved than the NDAs, arose in a genomic background ancestral to AMHs, and were maintained in a relatively larger ancestral hominin population in which selection could act more efficiently. Accordingly, we expect RAs and NDAs to have different distributions of functional effects in introgressed human populations. While estimating effects of individual mutations is challenging, variant effect prediction algorithms (CADD and PolyPhen2) indicate that NDAs are generally more damaging than RAs (Figure S9, Figures S11-S13), consistent with a model of less efficient selection on NDAs than RAs over their histories. Consequently, coding or regulatory functions played by RAs should be more benign overall than those of NDAs, perhaps even beneficial. Thus, within the context of some introgressed haplotypes, the ancient RAs may have conferred a degree of “compatibility” that protected the linked NDAs from negative selection. Figure S9 Reintroduced alleles have different predicted fitness effects than Neanderthal-derived alleles. (A) Simulations indicate that the RAs persisting in modern Eurasian populations are consistently less deleterious than NDAs over 200 simulations (median selection coefficient RA=7.7e-5; NDA=1.9e-4, P ≈ 0, Mann Whitney U test test). (B) In modern European (EUR) populations, RAs are predicted to be significantly less deleterious than NDAs by CADD (median scaled CADD: NDA=2.7; RA=2.1; P ≈ 0). The upper tail of highly deleterious mutations is highlighted in the inset. Results are similar for unscaled scores. (C) At the haplotype level, the maximum RA CADD score per introgressed haplotype is significantly lower than for NDAs (median scaled max CADD: NDA=13.3; RA=5.8; P ≈ 0). This is in part due to the overall difference demonstrated in (B) and to the greater number of NDAs per haplotype. RAs are rarely the most deleterious variant per haplotype. Results in East Asian and South Asian populations are similar (Figure S12). Figure S10 Distribution of selection coefficients of introgressed variants in simulated modern Eurasian populations are similar between admixture fractions. Selection coefficients in Eurasians from SLiM simulations with high (0.04) and low (0.02) admixture fractions. Each boxplot summarizes the average selection coefficient of all alleles in each introgressed class in each of 100 simulated modern Eurasian populations. Figure S11 CADD scores for RAs (stratified as RAA and RHA) and NDAs in each of three populations. Normalized CADD scores for the introgressed variant classes (RAs and NDAs) with RAs separated into RAAs and RHAs. Considering RAAs and RHAs separately revealed that the RAAs are less deleterious than the RHAs (median scaled CADD score: RAA=1.91; RHA=2.23; P = 1.80e-89, Mann Whitney U test). This difference likely reflects the greater evolutionary conservation of RAAs. Results were similar across each superpopulation Figure S12 Max scaled CADD score per introgressed haplotype. The maximum scaled CADD score for each class of introgressed variant across introgressed haplotypes in each of three Eurasian populations. Maximum CADD scores of each class of RA (RAA and RHA) are much lower than those of the NDAs (P = 0, Mann Whitney U test). Figure S13 PolyPhen2 predicts RAs to be less damaging than NDAs. PolyPhen2 is more likely to classify RAs as “benign” in all three Eurasian populations. Conversely, NDAs are significantly more likely to be classified as “damaging” in both EUR and SAS populations. The y-axis reports the difference in PolyPhen category membership for each population (i.e., the fraction all RAs in population in the PolyPhen category minus the fraction of all NDAs in population in the PolyPhen category). Per population hypergeometric test is calculated on the enrichment (positive delta) or depletion (negative delta) for RA content within each PolyPhen category. Figure S14 RA fraction in introgressed haplotypes containing eQTL in GTEx tissues. Summary of the RA fraction among introgressed variants in Neanderthal haplotypes in Europeans (EUR). Boxplots show the distributions RA fractions of all haplotypes containing at least one introgressed eQTL (RA or NDA) in the given GTEx tissue (gray box plots). These distributions are then compared pairwise with distribution for introgressed haplotypes that contain no introgressed GTEx eQTL (top, blue boxplot; n=4237). Haplotypes containing GTEx eQTL have RA contents higher than non-eQTL containing haplotypes in 46 tissues, with 34 of the tissues (*) having a significantly higher the RA fraction (P<0.05, Mann Whitney U Test). Further analysis of RAs will also be relevant to studies of the genetics of ancient hominin populations. For example, tens of thousands of RAs that are present in Eurasians are not present in African populations. These ancient variants could both inform ongoing debates over differences in efficiency of natural selection between Africa and Eurasia (51–54), as well as provide a window into ancient genetic variation that was present in Africa over a half million years ago. CONCLUSIONS Here we show that Neanderthal introgression reintroduced alleles lost in to the ancestors of Eurasian populations and that many of these RAs have the potential to be functional. This illustrates the importance of accounting for shared ancestral variation among hominin populations and shows that hybridization events between populations have the potential to modulate the effects of bottlenecks on allelic diversity. Our findings open several avenues for future work on quantifying the evolutionary and functional dynamics of archaic introgression. Previous analyses of introgression have focused on alleles derived within the Neanderthal lineage; additional work is needed to account for the potential effects of RAs and their influence on the maintenance of Neanderthal ancestry. In short, reintroduced alleles must also be considered in analyses of Neanderthal introgression, at both the haplotype and genome scale.
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Post by Admin on Aug 30, 2020 23:49:37 GMT
Climate change occurring shortly before their disappearance triggered a complex change in the behavior of late Neanderthals in Europe: they developed more complex tools. This is the conclusion reached by a group of researchers from Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and Università degli Studi die Ferrara (UNIFE) on the basis of finds in the Sesselfelsgrotte cave in Lower Bavaria. Neanderthals lived approximately 400,000 to 40,000 years ago in large areas of Europe and the Middle East, even as far as the outer edges of Siberia. They produced tools using wood and glass-like rock material, which they also sometimes combined, for example to make a spear with a sharp and hard point made of stone. From approximately 100,000 years ago, their universal cutting and scraping tool was a knife made of stone, the handle consisting of a blunt edge on the tool itself. These Keilmesser (backed, asymmetrical bifacially-shaped knives) were available in various shapes, leading researchers to wonder why the Neanderthals created such a variety of knives? Did they use different knives for different tasks or did the knives come from different sub-groups of Neanderthals? This was what the international research project hoped to find out. Keilmesser are the answer "Keilmesser are a reaction to the highly mobile lifestyle during the first half of the last ice age. As they could be sharpened again as and when necessary, they were able to be used for a long time—almost like a Swiss army knife today," says Prof. Dr. Thorsten Uthmeier from the Institute of Prehistory and Early History at FAU. "However, people often forget that bi-facially worked knives were not the only tools Neanderthals had. Backed knives from the Neanderthal period are surprisingly varied," adds his Italian colleague Dr. Davide Delpiano from Sezione di Scienze Preistoriche e Antropologiche at UNIFE. "Our research uses the possibilities offered by digital analysis of 3-D models to discover similarities and differences between the various types of knives using statistical methods." The two researchers investigated artifacts from one of the most important Neanderthal sites in Central Europe, the Sesselfelsgrotte cave in Lower Bavaria. During excavations in the cave conducted by the Institute of Prehistory and Early History at FAU, more than 100,000 artifacts and innumerable hunting remains left behind by the Neanderthals have been found, even including evidence of a Neanderthal burial. The researchers have now analyzed the most significant knife-like tools using 3-D scans produced in collaboration with Prof. Dr. Marc Stamminger and Dr. Frank Bauer from the Chair of Visual Computing at the Department of Computer Science at FAU. They allow the form and properties of the tool to be recorded extremely precisely. "The technical repertoire used to create Keilmesser is not only direct proof of the advanced planning skills of our extinct relatives, but also a strategical reaction to the restrictions imposed upon them by adverse natural conditions," says Uthmeier, FAU professor for Early Prehistory and Archaeology of Prehistoric Hunters and Gatherers. Other climate, other tools What Uthmeier refers to as 'adverse natural conditions' are climate changes after the end of the last interglacial more than 100,000 years ago. Particularly severe cold phases during the following Weichsel glacial period began more than 60,000 years ago and led to a shortage of natural resources. In order to survive, the Neanderthals had to become more mobile than before, and adjust their tools accordingly. The Neanderthals probably copied the functionality of unifacial backed knives, which are only shaped on one side, and used these as the starting point to develop bi-facially formed Keilmesser shaped on both sides. "This is indicated in particular by similarities in the cutting edge, which consists in both instances of a flat bottom and a convex top, which was predominantly suited for cutting lengthwise, meaning that it is quite right to refer to the tool as a knife," says Davide Delpiano from UNIFE. Both types of knife—the simpler older version and the newer, significantly more complex version—obviously have the same function. The most important difference between the two tools investigated in this instance is the longer lifespan of bi-facial tools. Keilmesser therefore represent a high-tech concept for a long-life, multi-functional tool, which could be used without any additional accessories such as a wooden handle. "Studies from other research groups seem to support our interpretation," says Uthmeier. "Unlike some people have claimed, the disappearance of the Neanderthals cannot have been a result of a lack of innovation or methodical thinking." Explore further Siberian Neanderthals originated from various European populations More information: Davide Delpiano et al, Techno-functional and 3D shape analysis applied for investigating the variability of backed tools in the Late Middle Paleolithic of Central Europe, PLOS ONE (2020). DOI: 10.1371/journal.pone.0236548
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Post by Admin on Aug 31, 2020 7:50:00 GMT
Techno-functional and 3D shape analysis applied for investigating the variability of backed tools in the Late Middle Paleolithic of Central Europe Abstract In the Late Middle Paleolithic of Central Europe, two main cultural complexes have been distinguished: the Micoquian or Keilmessergruppe (KMG), and the Mousterian. Their differences mainly consist in the frequence of some retouched tools and the presence of bifacial technology. When these industries coexist, one element of discussion is the application of different concepts to manufacture tools with the same techno-functionality. This is particularly true for backed artifacts, such as Keilmesser (backed, asymmetrical bifacially-shaped knives) opposed to flake-tools equipped with a natural or knapped back. We conducted a techno-functional analysis of the backed tools from the G-Layer-Complex of Sesselfelsgrotte, one of the main Late Middle Paleolithic sequences in Central Europe, characterized by a combination of KMG and Mousterian aspects. In order to better understand the morpho-metrical data, 3D scans were used for recording technical features and performing semi-automatic geometric morphometrics. Results indicate that the techno-functional schemes of Keilmesser show a moderate variability and often overlap with the schemes of other typological groups. Within bifacial backed knives, a process of imitation of unifacial flake tools’ functionaly was recognized particularly in the cutting edge manufacturing. Keilmesser proved to be the long-life, versatile version of backed flake-tools, also due to the recurrent valence as both tool and core. This is why Keilmesser represent an ideal strategic blank when a mobile and multi-functional tool is needed. Based on these data, it is assumed that the relationship between Mousterian and KMG is deeply rooted and the emergence of KMG aspects could be related to constrained situations characterizing the long cold stages of the Early Weichselian. A higher regional mobility caused by the comparably low predictability of resources characterized the subsistence tactics of Neanderthal groups especially at the borders of their overall distribution. For this reason, Keilmesser could have represented an ecological answer before possibly becoming a marker of cultural identity. Citation: Delpiano D, Uthmeier T (2020) Techno-functional and 3D shape analysis applied for investigating the variability of backed tools in the Late Middle Paleolithic of Central Europe. PLoS ONE 15(8): e0236548. doi.org/10.1371/journal.pone.02365481. Introduction: Defining Mousterian and Micoquian dichotomy in Central Europe The technological variability through time and space that characterizes the 250,000 years of occupation of Central Europe by Neanderthal groups is a direct evidence for the plasticity of their behavioral strategies, which do not appear to have been static, but, on the contrary, complex and changeable, particularly during the last phase of their presence in Europe [1,2]. Numerous analysis of Middle Paleolithic innovations suggest that they were triggered by a complex combination of several factors, which have been integrated in explanatory models for the variability in some of the major techno-complexes within the Middle Paleolithic contexts [3–9]. The ecosystem in which these groups interacted, the major activities carried out with the knapped tools at different sites within the territories used, the cultural background that some groups shared: each one of these interdependent elements is a single component of a complex ensemble that may have contributed to common changing (and innovation) processes. Similarly, social factors, such as group size, the density of social networks or the long-term transfer of information, should not be omitted [10]. The two main lithic industries that are until today dominating the discussion about the Late Middle Paleolithic in Central Europe are the Mousterian and the Micoquian [11,12]. It was long thought that these two entities, which are in turn fragmented into further techno-complexes characterized by different technological concepts and/or tool types, correspond to distinct Neanderthal populations, at least in terms of technical behavior [12–14]. However, the specific definitions of the techno-complexes involved, as well as their chronological frameworks, were biased due to different histories of studies, terminological misunderstandings, and lack of reliable chronostratigraphic contexts. In the recent past, it became more and more difficult to explain the bonds recognized within this presumed dichotomy, and consequently to quantify how much of those are rooted in the cultural sphere or, on the other hand, in the behavioral economy [15]. The Micoquian concept itself incorporates different meanings: the Micoquian sensu lato is a Middle Paleolithic industry whose lithic assemblages are characterized by asymmetrical or elongated bifacial tools with concave edges [14,16]. This Micoquian s.l. was defined by Otto Hauser based on layer H, complex VI at La Micoque [17]; the currently unknown stratigraphic position and the distribution of the original material on numerous collections make a modern and general analysis difficult. According to a recent reassessment [17], Micoquian-type bifacials are indeed present in that layer and occur together with Levallois artifacts, but the questionable chrono-stratigraphy casts doubt on any large-scale hypothesis derived from the type site assemblage. The Micoquian s.l. at that time was considered as a late Lower Paleolithic industry, chronologically positioned between Acheulean and Mousterian. Gerhard Bosinski linked the Micoquian to a series of Middle Paleolithic lithic industries typical of Central Europe characterized by different bifacial tool types and dated to the Eemain and the Early Weichselian (MIS 5) [12]. He developed a qualitative morphological approach by using presence or absence and typocial combination of fossile directeurs to create formengruppen; the morphological variability of a fossil directeur within a formengruppe may lead to a further subdivision into inventory types. For the Micoquian, the most indicative fossil directeur was the asymmetrical backed biface or keilmesser (KM). Afterwards, this category was enlarged by Stephan Veil who included bifacial leaf-shaped tools in the typical Micoquian toolkit [18], and A. Pastoors [19], who could show that large handaxes are also an integral part of the Micoquian. Despite the fact that these—and other tool types such as small handaxes or groszak [9]- also occur frequently in the respective assemblages, the common denominator of Central European Micoquian is still the Keilmesser. In addition to the term “Micoquian”, different alternative terms have been proposed for assemblages from Central Europe, mainly stressing a strong correlation with some bifacial tool forms, e.g. Micoquo-Pradnikian or Asymmetrical Knives Assemblages (AKA) [20,21] or the most common Keilmessergruppen [18,22,23]. The chronological framing of the Keilmessergruppen in Central Europe is still debated. According to few debated Polish sites (mainly Dzierzyslaw I and Bisnik cave), some isolated Micoquian features may appear as early as MIS 6 [14,24,25]. However, at the moment two main schools of thought exist. Based on the stratigraphies of German sites (mainly Königsaue, Buhlen/Oberer Fundplatz, Balver Höhle, Neumark Nord-2), the “long chronology” postulates the presence of the Central European Micoquian during the entire first part of the last glacial cycle (starting after Eemian, e.g. from MIS 5d to MIS 3) [26]. To the contrary, a “short chronology” restricted to end of MIS 4 and the first half of MIS 3, based on the assumption that assemblages of Keilmessergruppen are confined to cold environments occuring in Central Europe not earlier than MIS 4, has been then proposed for the entire Central European Keilmessergruppen [9,27,28]. Sites central to the arguments for a “long chronolgy”, such as the Balver Höhle, are still under debate between those who favor the first [29] or the second hypothesis [9,27] for the integrity of their stratigraphical sequences. Equally disputed are a number of supposingly early sites like Wylotne and Zwierzyniek [30] as well as those of Zwolén [31] and German sites of the Ruhr region [32]; the latter both represent fluvial archives with problematic site formation processes. Based on geological data, Königsaue was originally dated to MIS 5a [33], but direct AMS-dates on resin [34], and subsequently on bone [35] from the older layer A, has shifted the attribution to MIS 3 (44.5–46 ky). Recently obtained absolute dates (93±7 ky) from Neumark Nord 2/0 are in good agreement with the environmental studies and support an onset of the Keilmessergruppen during MIS 5b-c [36] and, therefore, give new arguments for the “long chronology”. Both the two models agree that a large number of sites from secure stratigraphical contexts and with reliable absolute dates fall into a period between the end of MIS 4 and the first part of MIS 3. Among these sites are Sesselfelsgrotte [37,38], Pouch [39], Verpillière I and II [40], Ciemna and Oblazowa [41,42], Pietraszyn 49a [43], Wroclaw-Hallera Avenue [44] and Kůlna [45]. Other contexts with dates falling into MIS 3 age are Salzgitter-Lebenstedt [19,46] and Lichtenberg [18], however characterized by complex open-air sequences or unsecure association between dates and human occupation [26] (Fig 1). Fig 1. Map of Central-Western Europe during GI 12 (46.8–44.2 ky) with Digital Elevation Model (base topography–ETOPO, 2011; ETRS_1989_LAEA_152 projected coordinate system) developed by Davide Margaritora and location of sites named in the paper: 1) La Micoque; 2) Abri du Musée; 3) Champ Grand; 4) Grotte de la Verpiliére; 5) Kartstein; 6) Neandertal; 7) Balver Höhle; 8) Bühlen; 9) Bockstein-III; 10) Klausennische; 11) Sesselfelsgrotte; 12) Zeitlarn-I; 13) Weinberghöhle; 14) Neumark Nord; 15) Königsaue; 16) Salzgitter-Lebenstedt; 17) Lichtenberg; 18) Moravsky-Krumlov IV; 19) Kůlna; 20) Dzierzyslaw-I; 21) Pietraszyn 49a; 22) Oblazowa; 23) Zwierziniek; 24) Wylotne; 25) Ciemna; 26) Bisnik; 27) Zwolén; 28) Tata; 29) Wroclaw-Hallera Avenue; 30) Pouch. Depending on the study approaches and analytical methodologies, the relationship between the Keilmessergruppen on the one hand, and the Mousterian on the other, has been considered with different points of view: two independent cultural units differentiated on a chronological base [12], in which Micoquian elements develop directly from late Acheulean assemblages [21], or two cultures characterized by a parallel development (evolution buissonant) [14], up to the recognition of a deep functional interrelation between both entities, expressed by the term “Mousterian with Micoquian Option (M.M.O.)” [9], which will be used in this paper as well. According to this interpretation, Keilmesser and, more broadly speaking, the Micoquian bifacial tool technology, is a specific strategy to prolongate the use life of lithics by resharpening, which is at the same time applied within particular functional- or seasonal-related circumstances. The fact that the Micoquian bifacial tool technology is combined with different technological concepts for the manufacture of unifacial tools also typical for the Mousterian, like the Levallois, Quina and/or Discoid core reduction concepts, questions the significance of Micoquian features alone as independent markers of Late Middle Paleolithic entities [47]. The flake-débitage technologies, the typology of the unifacial flake-tools and bifacial tools have always been considered the main variables in any differentation between the Mousterian and the Keilmessergruppen/M.M.O.. However, for a long period most attempts to identify and classify Central European Keilmessergruppen/M.M.O. occurences focused on the presence or absence of bifacial tools and their variability, while putting less attention on simple unifacial tools. The main attention was on the eponymous Keilmesser, the leaf-shaped bifaces (Faustkeilblätter), the partially foliated (Halbkeile) and the small triangular bifaces (Fäustel), and a few typical, but rare tool types (bifacial scrapers, groszaki, etc.). This is in contrast to the Mousterian of Acheulean Tradition (MAT) [13,48], which was quite early understood as a combination of unifacial and bifacial tool concepts. The complexity of the general framework increased with the presence of a number of assemblages, mainly in North-Western Europe, that apparently could not be classified within one or the other entity (the “typological dilemma” according to Ruebens [49]), as they were characterized by the presence of Micoquian elements next to Levallois and laminar débitage systems, resulting in a new definition (Mousterian of bifacial tools–MBT [50]) recalling older ones such as the “Middle Palaeolithic Assemblages with Handaxes” (MPAH) by Kozlowski and Kozlowski [51]. Shifting the attention from the significance of the bifacial tools as fossils directeurs to a broader view, the importance of the relationship between the tools from débitage and façonnage and the productive concepts behind them started to emerge in different works of the so-called “techno-ecological approach” [6,52,53] aiming at techno-cultural distinction of the Neanderthal groups at the end of the Middle Paleolithic. The techno-ecological approach tries to place a tool into a context capable of understanding its complexity and effective cultural value. The tool fulfills functional needs, with different degrees of effectiveness and versatility, changing with direct relation to cultural and environmental constraints [54]. It is therefore necessary to integrate data from techno-functional, economic/strategic and behavioral approaches in a research design that allows to up-scale the small-scale complexity and variability of individual tools and tool types to a broader model in favor of a global understanding of more general dynamics. In particular, the different technological responses to similar needs may represent forms of cultural choices and/or environmental adaptation; in order to identify them, in-depth analyses are required besides precise chronometrical and paleoenvironmental framing. Here we present a reassessment of one of the most important artifact types in the classical distinction between the Mousterian and the Keilmessergruppen/M.M.O., e.g. backed bifacial knives, integrated in a broader sample of backed items stemming from different technological concepts selected among unifacial and bifacial artifacts. As we shall see, these are analytical appropriate elements due to analogies in their ergonomics, functionality and technological characterization. The analyzed pieces come from the G-layer-complex of Sesselfelsgrotte, which is one of the most significative sequences when investigating the relationship between Mousterian and Keilmessergruppen/M.M.O. The study combines techno-functional and morphometric approaches with a broader perspective integrating the strategic, ecological and cultural significance of the toolkits and, on a larger scale, the respective techno-complexes.
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Post by Admin on Aug 31, 2020 22:15:33 GMT
2. Relevance of backed tools within Late Middle Paleolithic assemblages Keilmesser is the tool type common to all the assemblages that are linked with the Keilmessergruppen/M.M.O. [23]. In general, Micoquian Keilmesser are widespread especially in Central and Eastern Europe, but also in the less frequent ocurrences of the Keilmessergruppen/M.M.O. in Western Europe (e.g. Verpilière I and II, Abrì du Musée in Les Eyzies de Tayac [40,55]). Apart from that, single pieces or related forms have been identified in very different, yet unrelated contexts from Africa to the Near East or even on the Iberian Peninsula [56,57], some of them dating back to the Middle Pleistocene [57]. However, it is only in the final Middle Paleolithic that they became increasingly standardized, numerically relevant and a common expression of more or less uniform lithic assemblages [26]. As suggested by the direct translation from the original German noun, the term Keilmesser describes a wedge knife and thus is merging the shape and the presumed function. In the literature, Keilmesser are sometimes referred to as “Faustkeilschaber” [58], backed bifaces (biface à dos [59]) or–in cases when combined with distinct outlines and/or features of manufacture—pradnik/prondniks [60] or Ciemna knives [51]. One of the most widely accepted definition [12] is that of a piece with an almost straight bifacial working edge opposite to a straight or angular back. This allows for a large variability of both in outline and cross-section asymmetrical tools with a carefully retouched, bifacial and sharp cutting edge, which is often shaping also a distal point, opposed to a usually rough and thick, often cortical prehensive part. The base of the tool is usually also thick and may have had a receptive function as well. If a distal point is present, a bifacially worked “bow” (distal posterior part) may form the “trait d’union” between the back and the cutting edge [23]. Typical in Keilmesser is the plano-convex/plano-convex cross-section shaped through flat retouch of the lower face to the cutting edge, and a corresponding convex direct retouch on the upper face, which can be simple or scaled. The cutting angle is usually acute and smaller than 60° [23,40,61] or only slightly larger [62]. In contrast to wider scrapers angles used with transversal motion, this is suggesting a function of a knife with longitudinal cutting motion. A reversal plano-convex section on the back is often applied in order to have a flat and a convex edge on each surface. Such an asymetrical volumetric scheme permits to maintain the effectiveness of the edge angles even after subsequent resharpening stages [53,61], and especially when the tool is reoriented to reverse the edge functions by using a second working edge opposite to the first one [63]. The long stages of use, reuse and recycling of Keilmesser are testified by the detachments of core-reduction flakes, thinning products and orthogonal or longitudinal retouch as well as lateral resharpening flakes. Typical of the shaping of the cutting edge is the “tranchet blow” technique testified in several Keilmessergruppe/M.M.O. sites [29,64,65]. It follows that the final morphology can vary, depending on the raw material properties, the degree of reshaprening and/or other ecological and functional factors. Although the definitions of Bosinski´s tool types are still valid, they are no longer used as fossils directeurs for distinct entities, e.g. his “inventory types” [12]. It became common sense that simple generalizations on Keilmesser are misleading; instead, an in-depth working-step analysis of larger samples of objects is hence required to comprehend the different individual biographies before generating a general model for a given assemblage or site [9,19,52,66]. As a matter of fact, the Keilmesser tool concept contains objects which share the same ergonomic properties within the human–tool interaction system: the hand-held knife usage scheme is built around the direct opposition between the cutting edge and back. This backed tool, whose precise functions are however still to be confirmed by large scale use-wear analysis (e.g. cutting tools [18] or rather multi-functional [67]), already shows a marked variability in the macroscopical use-patterns that calls for an investigation from a techno-functional point of view. However, within the same assemblages and in the coeval European landscape, other backed tools exist. These are mainly unifacial and obtained through different or complementary technological concepts. Although they can possess similar ergonomics and schemes of prehension and use, they are still technologically different as they result from other concepts of tool manufacture and determination of the back. Particularly relevant in this regard, also in the light of the present study, is to understand the process of decision-making that leads to the use (and potential resharpening and discard) of artifacts obtained by (bifacial) façonnage on the one hand, and/or the preference of artifacts manufactured by different concepts of débitage on the other. This is even more so, as almost always the assemblages in question are characterized by a considerable number of flakes derived from core-reduction concepts. The flake-oriented technologies in the Keilmessergruppen/M.M.O. are basically the same than those of the Mousterian complexes. Because of this, some explanatory models built on the relationship between unifacial and bifacial toolsets have been raised to explain the variability of Keilmessergruppen/M.M.O. complexes. In this regard, the Mousterian of Micoquian Option (M.M.O) after Richter [9,68], was initially coined on the base of the assemblages of the G-Layers-Complex from Sesselfelsgrotte. According to him, the “Micoquian Option” is an increase in the relative frequency of bifacial tools, which correlates to proxies interpreted as being indicative for a more intense use of the lithic artifacts discared at a site, such as the ratio between simple scrapers and double/convergent scrapers or between notched and denticulated pieces. He concludes that the relative amount of discarded bifacial tools in a Micoquian context increases with a growing time of activity, e.g the length of the site occupation. This assumption has been questioned, among others, by Jöris, who argues with the absence of an independent confirmation of the model by faunal data, and emphazises some examples of ephemeral campsites where bifacial shaping is dominant (e.g. Lichtenberg) [23]. However, both base camps and ephemeral camps can bear long-life bifacial tools, whose origin and purpose can relate to several different tool biographies [52]. The technological nature of the flake industries of Mousterian tradition in Keilmessergruppen/M.M.O. contexts is quite diversified. Bosinski [12] and Kozlowski and Kozlowski [51] initially pointed out that Levallois concept was absent in the Micoquian assemblages of Central Europe. Quina débitage is present within the most ancient layers in Sesselfelsgrotte [9], in Bockstein III [69], while Discoid débitage is well attested in Kůlna cave all along the Micoquian sequence [53], as well as in several Polish assemblages being part of the so-called “Bockstein group” according to Kozlowski and Kozlowski [51]. In the most recent Keilmessergruppen/M.M.O. sites, Levallois débitage is however usually dominant, in both its recurrent centripetal and recurrent parallel/unipolar variants, as attested in Sesselfelsgrotte, Königsaue, Salzgitter-Lebenstedt and other sites [9,19,33,35,52]. Each of these core reduction concepts result in sets of flakes, some of which present a back opposed to a sharp edge. These backed artifacts are not only strictly technical in that thay maintain the core shape and convexities, but at the same time may also represent the objectives of the knapping operations. Unaware of their respective frequencies, their production is in any case indispensable due to the technological function in the cause of the respective core reduction. Depending on the reduction concept, these artifacts can have different shapes: thick, short and asymmetrical when being part of the Quina concept [9,70,71], thick, short and at times pointed and/or asymmetrical within the Discoid one [53,72], and thinner and more elongated in case of the éclat debordants obtained by the Levallois concept [73]. The differences do not only lie in the morphology of the backed blanks, but imply distinct modification and curation strategies. In any case, the fact that they are used–indicated by the presence of retouched working edges—indicates that both their production and actual use results from different ecological and/or cultural responses to similar needs, e.g. a cutting edge opposite to a back. The reasons behind their manufacturing and discard need to be examined by taking into consideration their entire working life, from the conception to the techno-functionality until the (re)use potential. This is the starting point of the present study, which takes into exam the backed implements of a key sequence for the Mousterian/Micoquian relationship in central Europe. In the final Middle Paleolithic, backed tools acquired a particular importance from both a behavioral and a cognitive point of view. The post-determination of the back by means of abrupt direct retouch is well attested in different European techno-complexes [48,74,75]. This additional technical investment is supposed to enhances the performance by improving the prehensive grip or to adapt the tool for hafting. Unaware of the precise function, it is the standardization of prepared backed implements which is considered as an indicator of “modern behavior” due to the degree of problem solving behind their manufacture and the growing importance they acquire within MP-EUP and Middle Stone Age contexts [76–80]. 3. The case of Sesselfelsgrotte G-Complex 3.1 Stratigraphy The Sesselfelsgrotte is a small rock shelter located in the Lower Almühl valley near to the village of Essing, Lower Bavaria. Its stratigraphy represents one of the key sequences of the Upper Pleistocene in Central Europe. The site has been investigated by the University of Erlangen under the direction L. Zotz and G. Freund from 1964 to 1977 and again in 1981. Of the excavated area of 57 square meters, approximately 20 square meters are under the roof of the rock shelter. The stratigraphical sequence of 7 m is mainly formed by limestone débris and was subdivided into 18 geological layers, which were again differentiated into 35 sedimentological sub-layers. Its relevance is mainly due to the stratified preservation of 22 Middle Paleolithic occupations, which are characterized by numerous evident features in the form of fireplaces, well preserved lithic and faunal remains and the presence of Neanderthal remains [37] (Fig 2). Together with layers of the Upper Paleolithic and Mesolithic, they are embedded in a stratigraphical sequence that yielded environmental data (e.g. pedology, small mammal fauna, malacofauna) and was absolutely dated by numerous radiocarbon and TL-dates. The archeological sequence starts at the base with eight human occupations of the “Untere Schichten” (“lower layers”) from geological layer R to M, which are characterized by landscapes fluctuating from forestal to more open steppe [27] and dated to temperate interstadials at the beginning of the Weichselian glaciation (probably MIS 5c and 5a). The datation is confirmed by the development of the thickness of the enamel of molars in Arvicola terrestris, which clearly postdates the Eemian [81]. The Mousterian assemblages of the lower were classified as Mousterian with small dimensions (“Taubachian”), Charentien Type Ferrassie, Charentien Type Quina and Moustérien typique [27]. Above it follows the MIS 4, which is stratigraphically represented by sterile layers (L, K, I) indicating cold and arid conditions testified by the first appearance of mammoth and micro mammals typical of arctic tundra, accompanied by an increase of humidity in layer I [81]. The overlying layers H and G were termed “G-Complex” and contained thirteen subsequent occupations recognized in 60 cm of stratigraphy and dated to the onset of MIS 3 [9]. The following layer F is sterile and separates the G-Complex from a the last Middle Paleolithic frequentation of the site in layer E3 [82]. Above this, archaeologically sterile loess layers are correlated to the last glacial maximum (layer D). Human presence starts again in layers B and C with assemblages associated to the Magdalenian [83]. The Holocene Layer A with finds from the Mesolithic to the Middle Ages seals the sequence. Fig 2. Stratigraphical sequence of Sesselfelsgrotte: G-Complex layers are highlighted. 3.2 Lithic assemblage data The G-Complex yielded the remains of recurrent and–in part–intensive human occupations testified by numerous fireplaces situated both under the roof and in front of the drip line. From a sedimentological point of view, the presence of evident features and at least two living floors (sublayers G2 and G4) underline the excellent preservation conditions. These are equally attested by the many faunal remains and the fossils of three Neanderthal indviduals, one of which was identified as a foetus or neonatus [84]. Approximately 85,000 lithic artefacts were recovered from six sublayers of the G-Complex (G1, G2, G3, G4, G4a, G5) and from the underlying layer H. To also consider vertical post-depositional movements of artifacts typical for cave and rock shelter fillings, Richter [9] used the compostion of raw material units in excavation units (e.g. sediment removals in square metres) to identify coherent assemblages. Based on the assumption that every occupation has a specific raw material procurement and using the underlying precondition of a spatial connectivity of the artifacts discarded during each occupation, a cluster analysis resulted in 13 lithic assemblages. Whereas some were conform with the geological layers, others strechted over two. The occupations are thus characterized by different stratigraphical nuclei, different raw material spectra and/or different spatial distributions, the latter (but not always) restricted to the inner or the outer part and correlating with a fireplace. All 13 assemblages are associated to the already mentioned M.M.O., characterized by varying frequencies of bifacial tools and the presence of Levallois products. The occurence of backed bifacial knives in almost all assemblages allows to classify the archaeological record of the G-Complex as belonging to the Keilmessergruppen/M.M.O. Despite technological and typological close relations, the assemblages show a considerable variabilty: whereas some are dominated by Mousterian elements and have only few or none bifacial tools, others have frequencies of Micoqiuan bifacial tools that equal typical inventories of the Keilmessergruppen/M.M.O. The other aspect of variability in between the assemblages concerns the diversity of the raw material, which is based on a detailed sortation of artifacts according to outcrops and thought to mirror differences in the procurement strategies and/or the availability of raw material sources. The key for the model of the M.M.O. developed by Richter lies in his observation that the diversity of the raw material in both the Jurrassic cherts and quartzites underwent a cyclical change. Each of the four identified cycles begins with a high diversity of raw material units termd “Initialinventar” (“initial assemblage”), and ends with assemblages with a low diversity of the exploited raw material resources named “Konsekutivinventar” (“consecutive assemblages”). The raw material diversity correlates with a more Mousterian-like charactersitic of assemblages at the start of a cycle, and a pronounced Micoquian character (cause by maximal frequencies of bifacial tools) at the end. The ecological interpretations favored by Richter mainly bring back to two hypotheses, the first based on the knowledge of the local territory and the selection rate of the better raw material, and the second based on seasonal changes in the availiabilty of resources [9,47,68,85]: Whatever the interpretation, the different assemblages of the G-Complex clearly attest a diversity in the length of the site occupation, the mobility and the underlying land use strategies (Fig 3). This is indicated by the intra-cycle differences: each cycle begins with a small assemblage in which the typical Micoquian toolset is scarce and the tool ratio is strongly balanced towards scrapers. In the next phases of each cycle, an increase of the bifacial forms as well as of the laminar component and the denticulates is evident, the latter being–according to Dibble and Rolland [86]—proportional to the occupation length. The micoquian-denticulates-laminar package would hence increase according to this variable, attesting the shift from short-term campsites to base camps and accompanied by a change in land-use strategies [68]. Amongst the other main aspects of the lithic assemblage, it is worth mentioning that a microlithic component exists, which is manufactured on flakes obtained from advanced stages in the reduction of cores of local raw materials, e.g. from curated cores without cortex left. According to use wear, these tools, which are either “raclettes” (also termed “groszaki” or informal tools, served locally for the processing of soft materials and–most probably—of plants [87]. Finally, some Upper Paleolithic tool types are present, mainly untypical end-scrapers and burins. Regarding diachronic inter-cycles differences, a change in the technical systems of core redcution is attested: whereas the Quina concept is evident in the first cycle, the second is characterized by both Quina and Levallois products. During the third cycle, a preference of the Levallois recurrent centripetal method can be observed, and in in the fourth cycle cores of the Levallois recurrent parallel method gain more importance. A significant change is seen in the presence of the Quina concept in the lower part of the G-Complex and its lack in the upper part, resulting in the postulate of a M.M.O. A with Quina and M.M.O. B without Quina core reduction concept. This chronological sequence has been virtually extended to all the late Middle Paleolithic Keilmessergruppen/M.M.O. sites [9]. Fig 3. Seasonal cycles of occupation recognized by Richter (1997) for G-Complex layers. On the left, the mobility and resources exploitation patterns during the initialinventar (circulating land-use patterns during summer); on the right, the spatial behaviour during the konsekutivinventar (radiating land-use pattern during autumn). From Richter 2001. 3.3 Environmental data and chronology The large mammal fauna of the G-Complex has been examined for the respective sublayer. Due to the occasional lack of correspondence between the geological sub-layers and the stratigraphical nucleus of lithic inventories, a verification of the model based on seasonal changes in the availiabilty of resources will not be possible for every assemblage [88]. However, an analysis of the meso- and microwear of horse teeth from assemblages that show a stratigraphical conformity with excavation layers is under preparation. In sum, the G-Complex faunal assemblages contain the frequent remains of Mammuthus primigenius, documented starting from layer M (MIS 4), and woolly rhinoceros, but are dominated by reindeer (Rangifer tarandum) and horse (Equus sp.). Among the other species, chamois, ibex, wolf, fox and arctic fox are frequently found, too, while the remains of giant deer, bison, red deer and cave bear are few. Information about environmental and climate indicators which accumulated without human agency in the different layers is significant. Studies of small and micro mammals [81], birds [89], molluscs [90], pollens and charcoals [91] unanimously attest a progressive growth in temperature, humidity and extension of fores cover from layers L to H. In particular, the increase of pine, birch and mugwort indicates a transition from a glacial to a more temperate phase. In the G-layers, charcoals document the spread of Larix/Picea and the presence of Prunus, while the scots pine is the only left pine tree. However, among the pollen a decrease of arboreal species in favor of an increase of Poaceae is noted if compared to layer H. At the same time, small mammals’ species typical of cold environment and arctic conditions confirm a certain degree of climatic instability and indicate an open vegetation with only sparse forested areas. The G-Complex has been dated by 14C, TL and IR-OSL methods. Radiocarbon dates on bones and charcoals provided dates between 30.770 and 47.860 calBP [38], but from these, only dates coming from the inner part are supposed to be reliable due to contermination by running water in the oute part in front of the dripline. Therefore, the reliable radiocarbon time window is reduced to between 39.950 e 47.860 Cal BP [82]. Except for one deemed date, a series of TL dates on burnt flints of 56.0 ± 4.7 ky support the validity of the older absolute dates from the inner part [92]. In general, the chronological position of the G-Complex in MIS 3 is verified by absolute dates from the underlying M-layers, which provide a medium date of 73.2 ± 11.7 ky, consistently with an attribution to MIS 5a. All the available radiometric and environmental data are in agreement with a datation of the G-Complex (from layers H to G) to the beginning of MIS 3, framed within the Oerel-Glinde interstadial. The layers formed in a milder phase if compared to the previous ones (from L to I), but still characterized by a probable cooling between layer H and the G-layers. Therefore, a certain climatic instability is documented; though more humid and temperate, these conditions indicate a landscape of open larix/picea boreal forest (taiga), populated mainly by mammooths, reindeers and horses.
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Post by Admin on Sept 1, 2020 8:22:28 GMT
4. Materials The sample of artifacts analyzed in the present study was selected from the assemblages of the G-Complex of Sesselfelsgrotte, stored in the Prehistoric collection of the Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Institut für Ur- und Frühgeschichte, Kochstr. 4/18, 91054 Erlangen. Since one of the authors (T.U.) is responsible for the collection, no permits were required for the described study, which complied with all relevant regulations. The criteria for the basic population, from which the analyzed items were sampled, were the presence of a raw or retouched cutting edge, opposed to a blunt edge forming a back, which could be cortical, the result of knapping prior to the detachment of the piece, or prepared. These “backed tools” sensu lato fall into three main categories: Keilmesser, backed scrapers and backed flakes. The classifications were taken from Richter [9]. The first two groups consist of tools sensu stricto, determined according to an empirical-inductive approach by the identification of the technical investment to obtain the cutting edges. This investment, which we read as retouch, is a direct evidence of their intended or actual use. The third category is composed by potential tools, determined according to a hypothetical-deductive and technological approach. Through a series of techno-functional attributes (regularity, dimensions, ergonomics, handling, functionality) and by analogy with items of the aforementioned groups of tools sensu stricto, it is assumed that these were or could be used. The present study is focused on backed tools s.l. because: Their ergonomics and functionality are apparently simple and linear, because they are characterized by a clearly identifiable active and equally distict passive part; the potential function is ranging from knives to multifunctional tools. The broad analogies between retouched and unretouched as well as unifacial and bifacial backed tools allow different analytic approaches ranging from the techno-functional to the geometric morphometric. Backed items represent one of the main objectives of the lithic reduction concepts of both débitage and façonnage operations. They perfectly exemplify and summarize the two technological and cultural worlds of the Mousterian and the Micoquian: Keilmesser on the one hand are the eponymous tool of the Keilmessergruppen/M.M.O., and backed flakes (obtained via Discoid, Levallois or Quina technologies) on the other hand are, alongside with backed scrapers, the common Mousterian toolset. All in all, 347 backed tools were selected within the assemblages of the G-Complex, including 58 Keilmesser, 118 backed scrapers, 155 backed flakes and 18 bifacial tools without a lateral back that conventionally are classified as different variants of handaxes (e.g. Faustkeile, Halbkeile and Fäustel) (Table 1; see also Supplementary Information for a detailed database). These later differ from Keilmesser because of a general symmetry and the lack of a back opposite to the cutting edge. However, one potential prehensive part is usually at the base; in cases where the base was thick, handaxes were included in the sampled artifacts. Given their significance, almost all Keilmesser from the G-Complex (assemblages A01 to A10) were analyzed. For the other artefact types, a twofolded sampling strategy was employed: for assemblages from the last cycle (assemblages A01, A02 and A03), it was tried to include almost all artefacts that meet the defining parameters described above. For the remaining three cycles, tools with specific interventions on the back and those representating the dominant tool or blank types with a back were chosen. In sum, the sampling allows to analyze not only a complete cycle for quantitative and qualitative comparisons, but at the same time to draw a complete picture of the techno-functional variability of all occupations. Fig 4. Classes of cutting edge bevel in cross-section view. 5. Methods of analysis 5.1 Techno-functional analysis One method of analyzing and comparing lithic tools is the techno-functional approach according to Lepot [93] and Boëda [94], which has already been applied by several scholars for the study of Middle Paleolithic assemblages a whole, as well as for specific tool types [95–97]. The techno-functional approach considers a tool as an object for the transfer of energy applied by humans to alter material matter. To do so, tools are composed of three functional units or contacts: a prehensive unit, a receptive and a transformative one. This approach considers the entire lifetime of an implement from prior to its production until its abandonment, e.g. through all stages of the operational chain from planning of tasks, raw material procurement and reduction to the actual use and abandonment. The method is embedding morphological and technological aspects by identifying the tools’ targets and usage schemes through the analysis of single units and their internal relationships. Each tool is subdivided into its structural elements. If viewed upon from the perspective of tool use, backed tools usually have a “passive” part, which includes zones for the receptive\prehensive contacts, and a corresponding “active” part, which allows for the transformative contacts to the worked materials. The receptive\prehensive contacts (Boëda [94]: “Contact Préhensif”—CP) represent the tool’s subsystem aimed at handling it and receiving the energy from the user. On the artefact, it generally corresponds to the portion of the blank opposite or adjacent to the natural or retouched working edge. The CP can be produced or shaped through technical investment (e.g. retouch, lower or upper thinning), but may also be represented by the striking platform (e.g. the basal part) or cortical or knapped areas of the laterals, which were unaltered or produced prior to the detachment of the blank and therefore result from the core reduction technology. The energy applied on the CP may also, be controlled by an additional handle or other means to enhance the prehension. The transformative contact (Boëda [94]: “Contact Transfomatif”—CT) represents the tool’s subsystem aimed at releasing the energy and transforming the material on which the tool is used. On the artefact, transformative contacts can be identified macroscopically by the existence of a sharp tranchant usually produced by retouch and opposed or adjacent to the prehensive contact. For one and the same artifact, single or multiple CT can exist on the laterals, but also forming a point. At the same time, parts defined as a continuous cutting edge in most typological classifications, as it is the case for simple side scrapers, may represents several CTs (Lepot [93]). The CT can be shaped by flaking or by bifacial façonnage, and it may be subsequently retouched for better performance. Starting from the morphology and the organization of the contacts of the analyzed tools, the comparative part of the approach used here aims at the identification of recurrently applied technological and morpho-functional features, which allow to summarize the main aspects in one (or several) scheme(s). The schemes are reconstructed by a systemic approach that structures a series of elements and puts them into relation. Each resulting artifact system is reflecting a level of organization on a quite general scale, which allows to further investigate general questions related to its structural, technological and ergonomic elements. By integrating information about human-environmental interactions inferred by the site setting, the site function and the ecological frame of the occupations, it is possible to compare the mental concept of the tools and to interfere the relevance of the techno-functional needs and the various ecological constraints that their makers and users were confronted with. We collected data for attribute and morphometrical analysis (See Supplementary Information for a detailed database). Whereas part of the data was collected from the 3D scans of artifacts, others were recorded manually. Among these is the following series of morphological elements and technological features: the maximum width, length and thickness, the amount of cortex left on the surface (subdivided into six classes from 0 to 100%), the weigth, the blank type (e.g. flake, Kombewa-flake, plaquette, pebble or frost flake), the general shape and cross section. For each CT, the following data have been registered: cordal length, overall curval length, minimum and maximum active angle (measured with a manual goniometer in 5° intervals), the shape of the longitudinal profile (from both the top and the sagittal view), and–if present–the type and extension of the retouch (according to Bourguignon [71]). Particular attention was payed to the bevel, e.g. the dihedral surfaces which shape the cutting edge. Bevel types were recorded based on different classes numbered from 1 to 7 (from concave to flat to convex, with intermediate classes between), considering the relationship between cutting edge and the lower face first and then relationship between the cutting edge and he upper face; for example, a combination of flat and slighly convex results in the class 4–5 (Fig 4). For assessing the conception of the cutting edge, it has been distinguished between “predetermined” when formed by flaking prior to the detachment of the blanks and therefore embedded in the knapping system) or left raw and not retouched, and “post-determined”, indicating a manufacture through flaking of the blank´s edge (mainly by retouch). For the documentation of techno-functional units forming a points, we recorded the overall shape, the angles in plane and section, the transversal cross-section (measured at about 5 mm from the point), the active bevel and, finally, the technological conception (in classes: natural, flaking, retouched and mixed). For each CP, we also recorded the cordal length, the overall curval length, the minimum, medium and maximum thickness of the back, the sagittal profile, the technological conception (subdivided in natural, fracture, flaking, retouched and mixed), the angles of lower and upper edges as well as the presence of anthropic modifications of the back using parameters already applied for the analysis of backed artefacts from Fumane Cave, unit A9 [75]. Finally, the relationships between the different techno-functional units were analyzed. In addition to the reconstruction of the aforementioned schemes, we caluclated the quantitative and morphometric relationships between the active and passive parts and the type of dexterity as well as the potential pressure applied to the back inferred from the degree of bifacial symmetry of the artefacts. These data have direct implications for hypothesis about the lateralization of the analyzed tool; however, to securely access this aspect, a systematic and statistical approach, corroborated by experimental tests, would be necessary. Data concerning the raw material and the techno-typology of the blank (keilmesser, scraper, flake tool, other bifacial tool) were taken from past studies [9,27]. For data management, analysis, charting and basic statistics, we used the “ggplot2”, “MASS”, “FactoMineR” and “Tidyverse” packages of RStudio Version 1.2.5001, and Past 3.15 version.
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