Mion Leïa
email: mion.leia@gmail.com

Herrscher Estelle

André Guy

Hernandez Jérôme

Donat Richard

Fabre Magali

Forest Vianney

Salazar-García Domingo

The influence of religious identity and socio-economic status on diet over time, an example from Medieval France

Keywords: High Middle Ages, Christianity, Carbon isotopes, Nitrogen isotopes

In Southern France as in other parts of Europe, significant changes occurred in settlement patterns between the end of Antiquity and the beginning of the Middle Ages. Small communities gathered to form, by the tenth century, villages organized around a church. This development was the result of a new social and agrarian organization. Its impact on lifestyles and, more precisely, on diet is still poorly understood. The analysis of carbon and nitrogen isotopes in bone collagen from the inhabitants of the well-preserved medieval rural site Missignac-Saint Gilles le Vieux (fifth to thirteenth centuries, Gard, France) provides insight into their dietary practices and enables a discussion about its transformation over time. A sample of 152 adult individuals dated from 675 to 1175 AD (75 females, 77 males) and 75 specimens from 16 non-human species were analyzed. Results show the exploitation of freshwater, marine, and terrestrial ecosystems as well as various breeding practices specific to each species. The use of both C4 and halophyte plants for feeding domestic animals was also observed. Concerning human dietary practices, a change seemed to occur at the beginning of the tenth century with an increase of  15 N values and a decrease of  13 C values. This corresponds to the introduction of a significant amount of freshwater resources into the diet and could be related to the evolution of the Catholic doctrine. A concomitant diversification of access to individual food resources was also observed, probably linked to the increased diversity of practice inside a population otherwise perceived as one community.

INTRODUCTION

Historic studies show that from the end of the eighth century to the beginning of the thirteenth century, feudal lordship and parish networks were set up, initiating transformations in the economic and social structures of medieval Europe [START_REF] Feller | Paysans et seigneurs au Moyen Âge: VIIIe-XVe siècles, 2e édition[END_REF]. Recent years have seen a renewal of archaeological data from South-East France (Languedoc region), revealing new information on how the mechanisms of this new organization impacted the region. Village formations [START_REF] Schneider | Castra, vicariae et circonscriptions intermédiaires du haut Moyen Age méridional (IX e -X e siècle): Le cas de la Septimanie-Gothie[END_REF][START_REF] Maufras | Villae -Villages du haut Moyen Âge en plaine du Languedoc oriental: maillage, morphologie et économie[END_REF], the reorganization of the funeral space [START_REF] Treffort | Des tombes et des hommes: trente ans d'archéologie funéraire en France[END_REF], and land occupation [START_REF] Maufras | Aperçu des villae médiévales de la Vistrenque à Nîmes (Gard): répartition, formes et héritage antique. In: Villae and Domain at the end of Antiquity and the beginning of Middle Ages[END_REF] or the intensification of agropastoral activities [START_REF] Durand | La forêt languedocienne (fin VIIIe siècle-XIe siècle). In: Corvol-Dessert A (ed) Les Forêts d'Occident du Moyen Âge à nos jours: actes des XXIVes Journées Internationales d[END_REF][START_REF] Durand | The transformation of riversides: the example of the alluvial valleys of Languedoc and the lower Rhône Valley during the medieval period (9th-13th centuries)[END_REF]) are some of the many ways the people of Languedoc experienced changes in social, economic, and cultural organizations. This reorganization probably also impacted on the daily lives of individuals. To determine how, identifying individual diets through isotopic analyses of bone collagen is particularly relevant. Individual food choices are the expression of biological (i.e. what a person can digest), cultural (i.e., what a person is authorized and/or chooses to eat), and economic (i.e. what a person can afford to eat) constraints. Therefore, through food choices, it is possible to approach all aspects (sex, age, wealth, religious doctrines) that can influence the daily lives of individuals and discuss the social and economic structure in which they find themselves. Similarly, isotopic analysis of bone collagen is also particularly interesting because it enables a discussion of nutrition at an individual level [START_REF] Herrscher | Biogéochimie isotopique et anthropologie biologique: reconstitution des modes de vie du passé[END_REF] and, consequently, of the very fine variations in nutrition within a population and over time.

This method has already demonstrated its usefulness in identifying specific societal changes taking place in the early Middle Ages across Europe (e.g., [START_REF] Müldner | Chapter 16: Investigating medieval diet and society by stable isotope analysis of human bone[END_REF][START_REF] Hakenbeck | Diet and mobility in early medieval Bavaria: a study of carbon and nitrogen stable isotopes[END_REF][START_REF] Lightfoot | Changing cultures, changing cuisines: cultural transitions and dietary change in Iron Age, Roman, and early medieval Croatia[END_REF][START_REF] López-Costas | Fringes of the empire: diet and cultural change at the Roman to post-Roman transition in NW Iberia[END_REF][START_REF] Kaupová | Diet in transitory society: isotopic analysis of medieval population of Central Europe (ninth-eleventh century AD, Czech Republic)[END_REF][START_REF] Olsen | Isotopic anthropology of rural German medieval diet: intra-and inter-population variability[END_REF]Salazar-García et al. 2014a;[START_REF] Salazar-García | A combined dietary approach using isotope and dental buccal-microwear analysis of human remains from the Neolithic, Roman and Medieval periods from the archaeological site of Tossal de les Basses (Alicante, Spain)[END_REF][START_REF] Guede | Isotopic evidence for the reconstruction of diet and mobility during village formation in the Early Middle Ages: Las Gobas (Burgos, northern Spain)[END_REF]). Our study focuses on the Missignac-Saint Gilles le Vieux site, whose occupation dated from the middle of the fifth to the early thirteenth century AD illustrating the modifications of settlement, agropastoral, and funerary practices taking place in South-East France during this period as described by historians. The presence of osteoarcheological material from both humans and non-human animals recovered at the site (Maufras et al. in press) provides the potential to assess (1) changes to dietary habits according to societal modifications occurring across time and (2) the relationships between biological characteristics and individual dietary choices.

MISSIGNAC-SAINT GILLES LE VIEUX

Missignac-Saint Gilles le Vieux is a rural site in South-East France (Aimargues, Gard), ca. 15 km from the Mediterranean Sea. It is located on a coastal plain of the Languedoc region at the edge of two rivers, the Vidourle and the Cubelle (Fig. 1). Discovered in 1995 [START_REF] Barberan | Structures agraires aux abords de Saint-Gilles le Vieux de la préhistoire au Moyen Âge, Aimargues "Madame[END_REF][START_REF] Maufras | Aperçu des villae médiévales de la Vistrenque à Nîmes (Gard): répartition, formes et héritage antique. In: Villae and Domain at the end of Antiquity and the beginning of Middle Ages[END_REF]Mercier 2002, 2006), extensive excavations were conducted in 2013 (Maufras et al. in press). Early medieval occupation occurred between the end of the fifth century and the beginning of the thirteenth century AD. Eight hundred fifty-two burials, as well as contemporaneous settlement structures and several hundred grain pits, were excavated. The site is divided into six phases numbered from 1 to 6 (Table 1), corresponding to different changes in the site's occupation (Maufras et al. in press).

Phase 1 corresponds to the beginning of the settlement, around the middle of the fifth century, characterized by small independent agricultural units organized around a major regional road, probably near a newly transformed or abandoned Roman villa. No burials dated to this phase have been identified. During phase 2, the settlement continued in a similar pattern. Around 20 graves were discovered dating to this phase. Phase 3 sees the settlement become denser with the cohabitation of several family units, each associated with a funerary area. During phase 4, the increase in density intensifies, and the settlement begins to tighten. At the end of the tenth century (end of phase 4A), a church is constructed, and the settlement slowly begins to reorganize itself around it. As for the funerary aspect, the small family areas of phase 3 continue to be used despite the set-up of an ecclesial cemetery south of the church. During phase 5, the settlement's density reaches a peak. At the same time, the ecclesial cemetery slowly becomes the main burial ground, certainly acquiring a parish status, but small secondary areas are still in use. Finally, phase 6 corresponds to the quick decline of the settlement despite the reconstruction of the church at the middle of the twelfth century. The site is abandoned at the beginning of the thirteenth century in favor of the nearby castra Aimargues in a process of incastellamento [START_REF] Maufras | Villae -Villages du haut Moyen Âge en plaine du Languedoc oriental: maillage, morphologie et économie[END_REF]. Consequently, the funeral use is reduced. The burials are located directly above the western façade of the church and to the north of it, as the ecclesial cemetery continues in use.

Funeral practices are quite homogenous during the period of usage of the site. Pit burials constitute the best represented funerary architecture on the site but also within each phase. The use of stone and wood is anecdotal with only 4% of the tombs identified using stone outside the roofing and 1% having a wooden construction [START_REF] Hernandez | Les ensembles funéraires de Missignac à travers le temps[END_REF]Maufras et al. in press). The other types of architecture consist of mixed forms, which combine the use of stone with wood and complete stone chests. The latter, which did not exist at the beginning of the funerary occupation, only became common during phases 5 and 6, and was concentrated in the enclosed cemetery to the south and along the western façade of the church. The dead appear stripped of their material possessions before being deposited in the tomb except for their clothes and in some rare cases, a shroud. No ornaments or other accompanying accouterments have been discovered, compatible with the rules recommended by the Catholic Church [START_REF] Hernandez | Les ensembles funéraires de Missignac à travers le temps[END_REF]. The 852 burials contained 900 individuals. The demographic structure of the population presents two anomalies. Firstly, there are few children present who died before reaching 1 year of age. The infants and young children identified have been discovered in areas reserved for them [START_REF] Donat | Les habitants de Missignac[END_REF]. Secondly, the population shows a significant proportion of males. Indeed, they are 1.6 times more numerous than females. Identified males and females (328 adults) are spread all over the funeral sectors of the site. Therefore, the sex ratio does not seem to be associated to the presence of funeral areas reserved to females outside of the excavation site. The village could have welcomed, throughout its occupation or massively at a given time, a group of males devoted to the practice of one or more specific activities [START_REF] Donat | Les habitants de Missignac[END_REF]. It is interesting to note that some of those males are distinguished by their high stature. The health status of the population reflects a generally unfavorable epidemiological context. There is a high frequency of individuals exposed to various chronic or acute diseases of infectious or nutritional origin such as tuberculosis or leprosy. The adult population is characterized by a high frequency of traumatic injuries, particularly fractures, which affect both males and females. Osteological data show that individuals have been highly exposed to repetitive biomechanical injuries and constraints, suggesting intense labor [START_REF] Donat | Les habitants de Missignac[END_REF]. The faunal study of the site reports that cattle (Bos p. taurus), pigs (Sus scrofa domesticus), and sheep (Ovis aries) and goat (Capra a. hircus), which form the domestic triad, represent the major sources of meat in the diet [START_REF] Bardot-Cambot | Étude archéozoologique: ostéologie, conchyliologie[END_REF]. Chicken (Gallus gallus domesticus) and probably equids (Equus asinus and Equus ferus caballus) were also consumed, but more anecdotally. Wild specimens are sparse, and marine shells are virtually non-existent despite the proximity to the sea. Cattle were slaughtered in adulthood: the older ones once their working lives were over (milking, reproduction), and the younger ones when they proved themselves unsuitable for certain tasks (locomotion difficulties, sterility of a female, violence of an animal). Sheep and goats were preferentially slaughtered after the age of 3. Most of the pigs were slaughtered before adulthood. All those species were raised locally [START_REF] Bardot-Cambot | Étude archéozoologique: ostéologie, conchyliologie[END_REF], and the marsh near the site appears to have been exploited for grazing [START_REF] Pradat | Aimargues -Madame -Saint-Gilles le Vieux[END_REF]. Some fish remains have been retrieved. ). The relatively small size of the fish discovered raises the issue of overfishing at the Missignac site during the beginning of the Middle Ages [START_REF] Cravinho | Etude de l'ichtyofaune[END_REF]. Finally, agricultural production, as documented by the preserved material, seems to be concentrated on wheat and barley with legumes (mainly lentils and vetches). Rye, oats, and millet are also present, but more anecdotally. Legumes (cloves, alfalfa, lentils) seem to have been used as fodder, just like barley [START_REF] Pradat | Aimargues -Madame -Saint-Gilles le Vieux[END_REF].

CARBON AND NITROGEN ISOTOPE ANALYSES FOR DIETARY RECONSTRUCTION

Vertebrate bone tissue assimilates the carbon and nitrogen found in the diet. An isotopic fractionation in favor of the heavy isotope occurs during the incorporation of those elements in the collagen of bones. For nitrogen, the enrichment between  15 N values of diet and collagen and between two consecutive trophic levels of the same trophic chain is comprised between 3 and 5‰ (DeNiro and Epstein 1981; [START_REF] Minagawa | Stepwise enrichment of 15 N along food chains: further evidence and the relation between δ15N and animal age[END_REF] but can vary from 1 to 7‰ [START_REF] O'connell | The dietbody offset in human nitrogen isotopic values: a controlled dietary study[END_REF]. For carbon, the enrichment between  13 C values between diet and collagen is approximately of 5‰ but can vary accordingly to the quantity of proteins in the diet; indeed  13 C values of carbohydrate, fat, and protein are different [START_REF] Ambrose | Experimental evidence for the relationship of the carbon isotope ratios of whole diet and dietary protein to those of bone collagen and carbonate[END_REF][START_REF] Froehle | FOCUS: effect of diet and protein source on carbon stable isotope ratios in collagen: follow up to[END_REF][START_REF] Fernandes | Macronutrient-based model for dietary carbon routing in bone collagen and bioapatite[END_REF]. The variation in  13 C values of collagen between two consecutive trophic levels of the same trophic chain is about 1‰ [START_REF] Bocherens | Trophic level isotopic enrichment of carbon and nitrogen in bone collagen: case studies from recent and ancient terrestrial ecosystems[END_REF][START_REF] Krajcarz | Collagen-to-collagen prey-predator isotopic enrichment ( 13 C,  15 N) in terrestrial mammals-a case study of a subfossil red fox den[END_REF]. Therefore, the isotopic ratios of carbon and nitrogen ( 13 C and  15 N) measured in bone collagen reflect the isotopic values of dietary resources, mainly protein. For both elements, plants at the base of the trophic chain condition the different isotopic ratios found throughout the food chain. Leguminous plants (Fabaceae) have isotopic nitrogen isotope values around 1‰ [START_REF] Schoeninger | Nitrogen and carbon isotopic composition of bone collagen from marine and terrestrial animals[END_REF]. The other plants have, on average  15 N values of 3‰ [START_REF] Bocherens | Paléoenvironnements et paléoalimentations : biogéochimie isotopique des vertébrés[END_REF]. Environmental conditions and soil chemistry can influence these values. Aridity tends to increase  15 N values, as well as some agricultural practices (manuring) [START_REF] Bogaard | The impact of manuring on nitrogen isotope ratios in cereals: archaeological implications for reconstruction of diet and crop management practices[END_REF]Fraser et al. 2011) or soil salinity (Virginia andDelwiche 1982;[START_REF] Britton | Stable isotope evidence for saltmarsh grazing in the Bronze Age Severn Estuary, UK: implications for palaeodietary analysis at coastal sites[END_REF]. Nonnitrogen-fixing marine plants tend to have  15 N values of around 7‰ [START_REF] Schoeninger | Nitrogen and carbon isotopic composition of bone collagen from marine and terrestrial animals[END_REF]. Physiology also impacts  15 N values. Ruminants have, on average, higher  15 N values than nonruminants [START_REF] Sponheimer | Nitrogen isotopes in mammalian herbivores: hair δ15N values from a controlled feeding study[END_REF]) despite a relatively similar trophic level. Furthermore, individuals subject to hormonal [START_REF] Fuller | Nitrogen balance and  15 N: why you're not what you eat during pregnancy[END_REF], pathological [START_REF] Katzenberg | Stable isotope variation in pathological bone[END_REF][START_REF] Olsen | The effects of pathology on intra-skeletal isotopic compositions (δ13C, δ15N) of bone collagen[END_REF], or nutritional [START_REF] Fuller | Nitrogen balance and  15 N: why you're not what you eat during nutritional stress[END_REF][START_REF] Mekota | Serial analysis of stable nitrogen and carbon isotopes in hair: monitoring starvation and recovery phases of patients suffering from anorexia nervosa[END_REF]) stress may have  15 N values that no longer reflect the trophic relationships of the ecosystems in which they live.

Trees, most plants from temperate and cold climates, and most aquatic plants follow the C3 photosynthetic pathway that results in  13 C values ranging from -36 to -22‰. Herbaceous plants like millet, sorghum, or sugarcane, in both temperate and warm environments, mostly follow the C4 photosynthetic process resulting in  13 C values ranging from -19 to -6‰ [START_REF] Smith | Two categories of 13 C/ 12 C ratios for higher plants[END_REF][START_REF] Deniro | Influence of diet on the distribution of carbon isotopes in animals[END_REF][START_REF] Deines | The isotopic composition of reduced organic carbon[END_REF][START_REF] Boutton | Stable carbon isotope ratios of natural materials: II. Atmospheric, terrestrial, marine, and freshwater environments[END_REF]. Plants'  13 C values are also affected by carbon sources. Terrestrial plants use atmospheric CO2 (-7‰ in pre-industrial times). Marine ones mainly use dissolved carbonate (0‰). Carbon for freshwater plants comes from both atmospheric CO2 and dissolved bicarbonate or carbonate, as well as from organic carbon, very depleted in 13 C, from waste and decomposition products from plants and animals living in the water [START_REF] Deniro | Stable isotopy and archaeology[END_REF][START_REF] Farquhar | Carbon isotope discrimination and photosynthesis[END_REF][START_REF] Dufour | Palaeodietary implications of isotopic variability in Eurasian lacustrine fish[END_REF][START_REF] Katzenberg | Stable isotope ecology and palaeodiet in the Lake Baikal region of Siberia[END_REF]. In brackish and estuarine environments, the mix of fresh and marine waters results in lower  13 C values than in marine ones but higher  13 C than in terrestrial ones (Salazar-García et al. 2014b). Similarly, a canopy effect can affect isotope ratios and can result in significantly lower  13 C values for plants from closed terrestrial environments compared to their counterparts from open ones [START_REF] Farquhar | Carbon isotope discrimination and photosynthesis[END_REF][START_REF] Heaton | Spatial, species, and temporal variations in the 13 C/ 12 C ratios of C3 plants: implications for palaeodiet studies[END_REF]. Finally, aridity, soil salinity, and physiological stress can result in higher  13 C values [START_REF] Tieszen | Natural variations in the carbon isotope values of plants: implications for archaeology, ecology, and paleoecology[END_REF].

MATERIAL

In total, 152 human individuals were sampled, all adult (a proximal phalanx per individual from a hand HPP or from a foot FPP, Table 2). They were selected to form a corpus of as many males as females (males: n = 77, females: n = 75) and of individuals from all the chronological phases where funerary occupation is documented. The chronological phase and sex of the individuals sampled are given with their elemental and isotopic values in Table 2.

In addition, 75 faunal remains found in the storage pits area and the garbage dump of the settlement area have also been sampled. They consist of specimens from the domestic triad (cattle, sheep/goat, pig), from less common species (chicken, donkey, horse, dog [Canis lupus familiaris] and goose [Anser cf anser]), marine and freshwater fishes (mullets, eel, European perch, northern pike), and terrestrial wild animals (toad [Bufo cf bufo], deer [Cervus cf elaphus], rabbit [Oryctolagus cf cuniculus], and duck [Anas cf platyrhynchos]). Bone samples are only from adult specimens. The chronological phase, species, elemental, and isotopic values of the specimen sampled are given in Table 3.

METHODS

Sex was determined using the probabilistic sexual diagnosis (PSD) method developed by [START_REF] Murail | DSP: a tool for probabilistic sex diagnosis using worldwide variability in hip-bone measurements[END_REF] and recently implemented in free software [START_REF] Brůžek | Validation and reliability of the sex estimation of the human os coxae using freely available DSP2 software for bioarchaeology and forensic anthropology[END_REF]). This method is based on ten metric variables measured on the coxae and allows sex estimation even on incomplete bones [START_REF] Brůžek | Validation and reliability of the sex estimation of the human os coxae using freely available DSP2 software for bioarchaeology and forensic anthropology[END_REF].

Age of death was estimated according to methods of [START_REF] Schmitt | Une nouvelle méthode pour estimer l'âge au décès des adultes à partir de la surface sacro-pelvienne iliaque[END_REF] and Owings Webb and Suchey (1985). Two age groups were used to estimate the relationship between age at death and diet: the class "20-39" regrouping the individuals aged of 20-29 years and 20-39 years and the "more than 40" regrouping the individuals aged of more than 40 years old including more than 50 and more than 60 (≥ 40: n = 38, 20-39: n = 30, Table 2).

Human and non-human animal bone collagen was extracted at the LAMPEA laboratory (UMR 7269, Aix-en-Provence, France). The bone samples were first cleaned by a sandblasting technique. Then, the mammalian (including humans) and avian bone samples were pre-treated using the protocol described by [START_REF] Longin | New method of collagen extraction for radiocarbon dating[END_REF] and modified by [START_REF] Bocherens | Isotopic biogeochemistry ( 13 C, 15 N) of fossil vertebrate collagen: application to the study of a past food web including Neandertal man[END_REF] (see Mion et al. 2016 for details). Fish bone samples were pre-treated using the protocol described by [START_REF] Richards | A Neolithic revolution? New evidence of diet in the British Neolithic[END_REF] adding an ultrafiltration step (>30kDa Amicon ultrafilters; [START_REF] Brown | Improved collagen extraction by modified Longin method[END_REF]). This protocol is less aggressive and more suitable for fragile fish bones [START_REF] Szpak | Fish bone chemistry and ultrastructure: implications for taphonomy and stable isotope analysis[END_REF][START_REF] Sealy | Comparison of two methods of extracting bone collagen for stable carbon and nitrogen isotope analysis: comparing whole bone demineralization with gelatinization and ultrafiltration[END_REF].

The carbon and nitrogen isotope ratio measurements were performed in the isotope facilities at the University of Cape Town (South Africa), using a Finnigan Delta plus XP continuous-flow isotope ratio mass spectrometer (Thermo Fisher Scientific, USA) after being combusted in the elemental analyzer Flash EA 1112 interfaced with it (Thermo Fisher Scientific, USA). Repeated analysis of three internal standards ("Merk Gelatin", "Valine" and "Seal Bone") determined an analytical error inferior to 0.01‰ for  13 C and  15 N.

For each sample, the extraction yield of collagen, the elemental composition of carbon and nitrogen, and the atomic ratio (C/N) were measured. These values were compared to the published ranges for well-preserved collagen in order to assess the samples' extracted collagen quality and the reliability of the isotopic data produced from each sample (more than 1% collagen yield, between 30 and 45% of carbon content, between 11 and 16% of nitrogen content, and C/N ratio between 2.9 and 3.6) [START_REF] Deniro | Stable isotopy and archaeology[END_REF][START_REF] Van Klinken | Bone collagen quality indicators for palaeodietary and radiocarbon measurements[END_REF]. The absence of correlation between those criteria and  13 C and  15 N values was also verified.

Correlations were tested using the Spearman test (Monte Carlo simulation with a level of accepted significance: p < 0.05 and R2 > 0.5). Differences between groups were tested with the exact Mann-Whitney and Kruskal-Wallis tests (Monte Carlo simulation, 1,000,000 replications, level of accepted significance: p < 0.05). The difference of variance between groups was tested with the Levene test. All the statistical tests were conducted on ©R (version 3.3.1) Rcmdr 2.3-0 with the Coin package. The statistical information for every test performed is given in the Supplementary Material.

RESULTS AND DISCUSSION

Collagen preservation

Collagen was extracted from 225 of the 227 bone samples. Unfortunately, the extraction for two fish bone samples (MISF27, MISF28) was not successful. Yields range from 1.9 to 19.7%, carbon contents range from 2.8 to 47.5%, nitrogen contents range from 0.8 to 15.9%, and C/N ratios range from 3.1 to 4.0 (median [first/third quartiles], yield = 11.1 [8.0/14.7], carbon contents = 41.2 [39.9/41.8], nitrogen contents = 15.1 [14.5/15.3], C/N ratios = 3.2 [3.2/3.2], n = 225). Sixteen samples have values not in accordance with the above mentioned preservation recommendations and were therefore excluded from the discussion (six human and ten faunal samples, Tables 2 and3). For the remaining 209 samples, yields and elemental values (carbon and nitrogen content, C/N ratios) are not correlated with the isotopic values (Spearman tests p > 0.05). Isotopic information is therefore considered as nondegraded and unaltered.

Faunal data and exploitation of local environments

Isotopic values for all faunal specimens are listed in Tables 3 and4 andillustrated 3 and4). This variability is explained by the presence of specimens from three different ecosystems: marine, freshwater, and terrestrial (Fig. 2).The marine ecosystem is represented by the mullet ( 13 C -11.4‰,  15 N 15.9‰). Its values are in accordance with the published values for specimens of ancient or medieval fish from the Mediterranean coasts (Table 5).

 13 C values of the two eels and two northern pikes range from -24.6 to -21.1‰ and their  15 N values from 7.8 to 10.8‰ (Fig. 2). They are consistent with published values for freshwater fish in Europe [START_REF] Dufour | Palaeodietary implications of isotopic variability in Eurasian lacustrine fish[END_REF][START_REF] Fuller | Carbon and nitrogen stable isotope ratio analysis of freshwater, brackish and marine fish from Belgian archaeological sites (1st and 2nd millennium AD)[END_REF][START_REF] Häberle | Inter-and intraspecies variability in stable isotope ratio values of archaeological freshwater fish remains from Switzerland (11 th -19 th centuries AD)[END_REF][START_REF] Colleter | Social status in late medieval and early modern Brittany: insights from stable isotope analysis[END_REF]. The duck's isotopic values fall in the same range and suggest a common habitat ( 13 C: -23.6‰,  15 N: 7.8‰, Fig. 2). Considering the surrounding freshwater environment around the site, those specimens are likely to be local.

Terrestrial animal  13 C values range from -21.0 to -17.6‰, and their  15 N values range from 3.7 to 10.8‰ ( 13 C: -19.8 [-20.2/-19.1],  15 N: 6.9 [5.7/8.4] n = 58, Fig. 2). One equid specimen shows a remarkable value of -17.6‰ (MIS F02) according to the variation of  13 C values for the other terrestrial animals, ranging from -21.0 to -18.2‰. This equid specimen seems to have a significant proportion of C4 plants in its diet in complement to C3 plants, probably millet as it is the only domesticated C4 plant in Europe for medieval times. The  13 C values of the other animals are consistent with diet where C3 plants are dominant [START_REF] Schoeninger | Nitrogen and carbon isotopic composition of bone collagen from marine and terrestrial animals[END_REF]. The range of their  15 N values reflects the presence of several trophic levels.

The isotopic values of the four wild herbivores (rabbit, deer) range from -20.9 to -20.1‰ for  13 C values and from 3.7 to 4.4‰ for the  15 N values (Table 4). They have the lowest isotopic values of carbon and nitrogen in the corpus of terrestrial animals as the exception of two sheep (Fig. 2). Feeding in a closed environment like the Mediterranean forests, with a low nutrient intake, is probably the source of these values [START_REF] Makarewicz | Foddering by Mongolian pastoralists is recorded in the stable carbon ( 13 C) and nitrogen ( 15 N) isotopes of caprine dentinal collagen[END_REF]. The toad's values are consistent with an insectivore diet from the same habitat ( 13 C: -19.6‰,  15 N: 7.3‰).

The chickens and the dog have  13 C values ranging from -19.6 to -18.2‰ and  15 N values ranging from 7.8 to 10.8‰. Those values are enriched compared to those of herbivorous specimen. This enrichment is coherent with a trophic enrichment, and as the isotopic values of chickens are comparable to those of human, a diet based on human wastes is likely (Fig. 3).

The pigs have lower  13 C and  15 N values than the chickens and dog ( 13 C: -19.9 [-20.1/-19.8],  15 N: 6.6 [6.2/7.1], n = 12, Table 4, Fig. 2). They are comparable to those of domestic herbivores (cattle, sheep, goat, equids, goose), which range from -21.0 to -17.6‰ for  13 C values and from 3.8 to 10.3‰ for  15 N values ( 13 C: -19.7 [-20.3/-19.0],  15 N: 6.9 [5.5/8.1], n = 34). Pigs seem, as a consequence, to have more plant input in the diet than chickens and dog. Historical sources attest that, in French medieval times, pigs had a mostly vegetal diet and were often brought into the forest where they fed on acorns, mushrooms, and occasionally, small animals (Audoin-Rouzeau 1998).

The isotopic values of the goat and equid specimens are noticeable for their great variability, which suggests different diets for each specimen, some of which are not consistent with the biotopes characterized by the other herbivorous sampled (Fig. 2). Those specimens could have been coming from a distant area, as hypothesized by archaeozoologists. Equids are indeed supposed to come from a different area used as transport for human traveling [START_REF] Bardot-Cambot | Étude archéozoologique: ostéologie, conchyliologie[END_REF]. Sheep and cattle can be separated into two groups based on their isotopic values. One group appears to have high carbon and nitrogen values, which may indicate a consumption of C3 halophyte plants (Fig. 2) [START_REF] Britton | Stable isotope evidence for saltmarsh grazing in the Bronze Age Severn Estuary, UK: implications for palaeodietary analysis at coastal sites[END_REF][START_REF] Müldner | Inferring animal husbandry strategies in coastal zones through stable isotope analysis: new evidence from the Flemish coastal plain (Belgium, 1st-15th century AD)[END_REF]. Those plants are documented in the Languedoc Mediterranean coast and are especially numerous in the Camargue area [START_REF] Braun-Blanquet | Les groupements végétaux de la France méditerranéenne[END_REF][START_REF] Géhu | Interprétation phytosociologique actualisée de quelques végétations psammophiles et halophiles de Camargue[END_REF]Médail 1994). The other group has lower  13 C and  15 N values which are representative of a C3 openarea plant consumption.

In summary, the great variability of animal values attests to the presence at the site of animals that lived in numerous biotopes. Wild animals were hunted probably from the forest near to the site. Fish came from the Mediterranean Sea and local freshwater rivers or lakes. Most of the domestic animals lived in a terrestrial habitat, although some cattle and sheep suggest the exploitation of coastal plains for breeding. The territory of Missignac would have been of around 750 ha (Maufras et al. in press) and would not have contained all the biotopes characterized by the isotopic values (i.e., coastal and marine), demonstrating that animal supply was not solely local at the site and confirms a carpology study of the marsh exploitation [START_REF] Pradat | Aimargues -Madame -Saint-Gilles le Vieux[END_REF]. The individual specific values of some goats and equids are unique in the species groups and in the domestic groups, and therefore, show an individual-specific diet. This could also be related to a medium-to long-distance animal supply for those species. Isotopic values of the domestic animals highlight also specific species-breeding practices for chicken and pigs. Pigs had an outdoor life as recorded in other medieval isotopic studies [START_REF] Hamilton | Pannage, pulses and pigs: isotopic and zooarchaeological evidence for changing pig management practices in later medieval England[END_REF][START_REF] Hammond | Pig diet in medieval York: carbon and nitrogen stable isotopes[END_REF]. Chicken had a diet mostly based on human waste that supposed a more constrained habitat.

Transformation of human isotopic signal over time

Isotopic values for all human specimens are listed in Tables 2 and6 and illustrated in Figs. 3 and4. Humans'  13 C values range from -20.2 to -17.8‰ and their  15 N values range from 6.7 to 13.1‰ ( 13 C: -18.8 [-18.9/-18.6],  15 N: 10.2 [9.6/10.8], n = 146, Tables 2 and6). Ten individuals show  13 C or  15 N values outside the variability of the whole population: H014, H030, H043, H055, H059, H066, H119, H124, H128, and H141 (> ± 2 SD from the mean, Fig. 3). Excluding the outliers, the  13 C values for humans range from -19.3 to -18.2‰, and their  15 N values range from 8.3 to 12.1‰ ( 13 C: -18.8 [-18.9/-18.6],  15 N: 10.3 [9.6/10.8] n = 136.

Male  13 C values range from -19.6 to -18.2‰, and their  15 N values range from 7.7 to 12.1‰ ( 13 C: -18.8 [-18.9/-18.6],  15 N: 10.3 [9.6/10.8], n = 75, Tables 2 and6). Female  13 C values range from -20.1 to -17.8‰ and their  15 N values range from 6.7 to 13.1‰ ( 13 C: -18.8 [-18.9/-18.6],  15 N: 10.1 [9.5/11.0], n = 71, Tables 2 and6). There are no statistically significant differences between the  13 C or the  15 N values of males and females for all the population or inside each chronological phase group (Mann-Whitney tests, Supplementary Material). Consequently, males and females had a similar protein diet at Missignac unlike other rural populations in Europe [START_REF] Reitsema | Stable isotope evidence for sex-and status-based variations in diet and life history at medieval Trino Vercellese, Italy[END_REF][START_REF] Kaupová | Diet in transitory society: isotopic analysis of medieval population of Central Europe (ninth-eleventh century AD, Czech Republic)[END_REF]. Seven of ten of the outliers previously listed are females maybe because of a short-term mobility before death. The median enrichment between the isotopic values of the domestic triad and humans is of 1.1‰ and 3.2‰ for δ13C and δ15N, respectively, which is in agreement with the trophic enrichment between two consecutive trophic levels [START_REF] Krajcarz | Collagen-to-collagen prey-predator isotopic enrichment ( 13 C,  15 N) in terrestrial mammals-a case study of a subfossil red fox den[END_REF]. Those four species could have been the main protein source for humans. This confirms the low consumption of terrestrial wildlife species, freshwater specimen, and secondary domestic species such as equids, chickens, or goats hypothesized from the zooarcheological studies (Fig. 3; [START_REF] Bardot-Cambot | Étude archéozoologique: ostéologie, conchyliologie[END_REF]. It is interesting to note that despite the presence of the sea, Missignac humans do not seem to have eaten substantial quantities of marine resources. Similarly, estuarine or brackish water resources do not seem to be a major source of protein.

Chronologically, isotopic values of the individuals dated from phase 4, phase 5, and phase 6 are statistically similar (Table 6, Fig. 4, Kruskal-Wallis tests, Supplementary Material). The isotopic values of the individuals from phase 3 are statistically different from the ones from the more recent phases pooled all together (Table 6, Fig. 4, Mann-Whitney tests, Supplementary Material).

The beginning of the Middle Ages is known as the Medieval Warm Period (Le Roy Ladurie 2004). In Mediterranean contexts like South-East France, this phenomenon is characterized by an intensification of aridity, an increase in temperature, and climate instability [START_REF] Vernet | Le  13 C de charbons de bois préhistoriques et historiques méditérranéens, de 35 000 BP à l'actuel. Premiers résultats[END_REF][START_REF] Jalut | Holocene climatic changes in the Western Mediterranean, from South-East France to South-East Spain[END_REF][START_REF] Araus | Changes in carbon isotope discrimination in grain cereals from different regions of the western Mediterranean Basin during the past seven millennia. Palaeoenvironmental evidence of a differential change in aridity during the late Holocene[END_REF]. Keeping this in mind, the chronological trend of human isotopic values could be linked to a change in the isotopic values of the main dietary resources, related directly to climatic variations. Indirectly, climate change could have also an impact on agricultural practices such as an increase use of manure. To test this hypothesis, isotopic values of the domestic triad from phases 2-3 and phases 4-6 were compared (Table 4). There is no statistical difference between  13 C and  15 N values of the phase 3 contemporaneous faunal specimens and the more recent ones (Mann-Whitney tests, Supplementary Material). Therefore, the difference of human isotopic values does not appear to be associated with a change over time of the main protein sources' isotopic values due to climatic conditions.

Overall, the trend of human isotopic values is also consistent with the introduction of freshwater resources into the food supply. The beginning of the village formation during phase 4 is therefore contemporaneous with a change in the consumption of food resources by the inhabitants of the site. Once the village begins to form, the freshwater resources remain to be a constant food source despite demographic or economic changes. Historical sources mention that at that time, a change in doctrine occurred: fish and aquatic resources, in general, were now authorized during the days of abstinence of the Catholic calendar (120/150 days per year, Montanari 2017). Therefore, the change in diet at Missignac at the beginning of the tenth century could be related to the religious affiliation of its inhabitants. The influence of the "aquatic resources" doctrine on diet has been highlighted in previous isotopic studies on early medieval populations [START_REF] Barrett | Identity, gender, religion and economy: new isotope and radiocarbon evidence for marine resource intensification in early historic Orkney, Scotland, UK[END_REF]Müldner and Richards 2007;[START_REF] Salamon | The consilience of historical and isotopic approaches in reconstructing the medieval Mediterranean diet[END_REF]. Moreover, our results show for the first time the application of this doctrine with the consumption of freshwater resources despite the proximity of the Mediterranean coast (less than 20 km).

Christianity is well established in the region before the tenth century. In Missignac, there is an object decorated with a chrismon (or Chi Rho) from the fifth century. There is, therefore, no doubt that by then, there already is at least one Christian individual if not a family at the site (Maufras et al. in press). The graves of the site are all laid out according to the Christian practice of the early Middle Age, even the early ones preceding the implantation of the church. The population is assumed to be predominantly Christian by the end of the seventh century. On the other hand, Missignac has its own customs, like that of burying the dead at the limits of the settlement, a custom that persisted even after the construction of the church. What the construction of the church brings is probably the permanent presence of a cleric, prior, or pastor, who regularly celebrates mass and certainly encourages his flock to follow the rules of the Christian Church such as fasting and burying the dead in the church cemetery. One may note that his influence is less effective on funeral practices even if rules concerning the unique funeral area are promulgated at the same times as those on fasting [START_REF] Treffort | Du cimiterium christianorum au cimetière paroissial: évolution des espaces funéraires en Gaule du VIe au Xe siècle[END_REF]. Indeed, at Missignac, dietary changes occurred faster than funeral changes. Most of the inhabitants followed the "funerary Catholic doctrine" only from phase 5 while the "dietary Catholic doctrine" would have been followed since phase 4.

The second trend is that the variance of  15 N values for individuals from phase 3 is statistically lower than that for individuals from phases 4 to 6 pooled all together (Levene tests, Supplementary Material, Fig. 4). Phase 3 peoples have a more homogenous protein diet than phase 4-6 individuals. There would be then a change in the individual access to animal protein once the village begins to be formed. Meat consumption is often linked with status during medieval times. People with wealth and/or power would be expected to eat more meat than less-privileged ones [START_REF] Montanari | Romains, Barbares, Chrétiens: à l'aube de la culture alimentaire européenne[END_REF]). This point is the base of numerous studies on the impact of socio-economic stratification on diet in the medieval isotopic literature (e.g., [START_REF] Lightfoot | Changing cultures, changing cuisines: cultural transitions and dietary change in Iron Age, Roman, and early medieval Croatia[END_REF][START_REF] Reitsema | Stable isotope evidence for sex-and status-based variations in diet and life history at medieval Trino Vercellese, Italy[END_REF][START_REF] Iacumin | C4-consumers in Southern Europe: the case of friuli V.G. (NE-Italy) during early and central Middle Ages[END_REF][START_REF] Alexander | Diet, society, and economy in late medieval Spain: stable isotope evidence from Muslims and Christians from Gandía, Valencia[END_REF][START_REF] Miclon | Social characterization of the medieval and modern population from Joué-lès-Tours (France): contribution of oral health and diet[END_REF][START_REF] Kaupová | Dukes, elites, and commoners: dietary reconstruction of the early medieval population of Bohemia (9th-11th century AD, Czech Republic)[END_REF]). However, it seems that at the beginning of the medieval period, access to animal products (including meat) was less strictly linked to wealth [START_REF] Montanari | La faim et l'abondance: histoire de l'alimentation en Europe[END_REF][START_REF] Gautier | Manger de la viande, signe extérieur de richesse? Le cas des îles Britanniques[END_REF]). It would be only after 1000 AD, in the context of the birth of feudal power, that meat begins to be reserved to elites [START_REF] Montanari | La faim et l'abondance: histoire de l'alimentation en Europe[END_REF][START_REF] Gautier | Manger de la viande, signe extérieur de richesse? Le cas des îles Britanniques[END_REF]. The increase of diversity in the diet of Missignac inhabitants from phase 4 could reflect this evolution of the social organization. Being more egalitarian at the beginning of the occupation, it would become more hierarchized with the establishment of the village, at least in terms of meat access.

At the same time, village development could result in an increased diversity of dietary choice. The highest variance of  15 N values is observed for the individuals of phase 5 (Table 6, Fig. 4), and most of the individuals with noticeable values are dated from the same phase (Table 2). This phase corresponds to the village maximum density and a noticeable diversification of the ceramic production (Maufras et al. in press). The variability of the isotopic data after phase 4 will then reflect the diversity of individual choice inside the village. Interestingly, this diet diversity seems to reach its peak while the inhabitants of Missignac can be perceived by the funerary archeology as a single community. Phase 5 is indeed the period during which most of the sepultures are located inside the ecclesial cemetery [START_REF] Hernandez | Les ensembles funéraires de Missignac à travers le temps[END_REF]. Isotopic values and funerary practices do not allow to see the same picture of Missignac population. Although they are influenced by the religious identity of the individuals, the implementation and the timing of this influence are different. Individuals who died before 40 have  13 C values ranging from -19.4 to -18.3‰ and  15 N values ranging from 6.7 to 13.1‰ ( 13 C: -18.8 [-18.9/-18.6],  15 N: 9.8 [9.1/10.4], n = 29, Table 6). Those who died after 40 years have  13 C values between -19.6 and -18.3‰ and  15 N values between 8.3 and 12.1‰ ( 13 C: -18.8 [-18.9/-18.6],  15 N: 10.4 [9.6/11.0], n = 35, Table 6). Statistically, for all the population, the two groups differ in their  15 N values. The oldest have higher values (Mann-Whitney tests, Supplementary Material). But, this difference disappears when the two groups are compared inside each chronological phase group (Mann-Whitney tests, Supplementary Material). Therefore, the difference observed for all the population is likely due to a sampling bias. The sample of ">40" individuals is mainly composed by individuals dated from phases 4 to 6 (24/35), and the difference detected is probably more linked to the chronological differences than to a difference of diet.

CONCLUSIONS

The agricultural use of at least five ecosystems is discernible from faunal  13 C and  15 N values at Missignac (n = 73): the Mediterranean Sea, a freshwater ecosystem, the forest, and two distinct open environments (among them, one dominated by halophytes). Some of the specimens analyzed (goat, equids) show individual-specific diet. This exploitation raises the question of a medium-to longdistance animal supply at Missignac and of its relation to other productive sites in the region.

The  13 C and  15 N values of Missignac human individuals (n = 146) are consistent with a diet mainly based on the domestic triad. No statistical differences between the isotopic values of males and females exist. A change in diet is observed concomitantly to the beginning of the medieval village formation at the first quarter of the tenth century. From this point onwards, freshwater resources seem to begin to be a considerable part of the inhabitants' diet and diverse individual access to food resources starts taking shape. Our data would suggest this is a consequence of both the religious identity of the individuals analyzed and the increased diversity of the population living at the site. The visible change in the diet happens at its own rhythm compared to that of the funerary practices. Thanks to isotopic diet reconstruction, it has been possible to properly assess the impact of religious identity and socio-economic status on the day-to-day life of Missignac individuals. The inhabitants that are one community by their unique cemetery can also be seen as multiple groups by their dietary habits highlighting the complexity of Christian medieval populations.

Virginia RA, Delwiche CC (1982) Natural 15 N abundance of presumed N2-fixing and non-N2-fixing plants from selected ecosystems. Oecologia 54(3):317-325

Owings Webb PA, Suchey JM (1985) Epiphyseal union of the anterior iliac crest and medial clavicle in a modern multiracial sample of American males and females. Am J Phys Anthropol 68:457-466 6)

  in Fig. 2. The  13 C values of the faunal samples range from -24.6 to -11.4‰ and their  15 N values from 3.7 to 15.9‰ ( 13 C: -19.8 [-20.3/-19.1]  15 N: 7.3 [5.8/8.6], n = 63, Tables

Fig. 1

 1 Fig. 1 Location of the site

  Most of the remains are from species living in freshwater environments (eel [Anguilla anguilla], northern pike [Esox lucius], European perch [Perca fluviatilis], cyprinids [Cyprinidae]; Cravinho 2018). Few marine species are also present (mullets [Mugilidae], flatfish [Pleuronectiformes], European bass [Dicentrarchus labrax]

Table 1 -

 1 Chronological phases of the High Middle Ages occupation at Missignac Saint Gilles le Vieux

	Phase		Date (AD)	Settlement	Funerary areas
	Phase 1		470-675	Small independent units	Not within the excavated area
	Phase 2		675-850	Small independent units	Twenty burials along the road
	Phase 3		850-925	Independent units Densification begins	An area for each settlement unit
		A	925-975	Grouping and densification -> proto-village	Previous areas still in use New ones are created
	Phase 4	B	975-1050	Construction of the church Spatial organization centered around church	Ecclesial cemetery installed south of the church Previous areas still largely in use
	Phase 5	A B	1050-1075 1075-1125	Grouping and densification continue until a peak -> village Occupation of site continues at its peak	Enclosed cemetery is the main funerary area Small areas still in use Cemetery extended into alleys at the east and west of the church
	Phase 6	A	1125-1175	Site begins to be abandoned Reconstruction of the church	Cemetery concentrated at the west of the church
		B	1175-1200 Site continues to be abandoned	Cemetery begins to be abandoned

Table 2 -

 2 Results of carbon and nitrogen isotope analyses and collagen quality criteria of human samples. Key: Samples in italic fall out with van Klinken (1999) conservation criteria and are not considered in the discussion. F=Female, M=Male, HPP=Hand proximal phalanx, FPP=Foot Proximal Phalanx, PP= Undetermined Proximal Phalanx, *="20-39" age class, **=">40" age class.

	LabCode	Chronological phase	Sex	Age at death (years)	Phalanx type	Yield (%)	Carbon content (%)	Nitrogen content (%)	C/N	 13 C (‰)	 15 N (‰)
	MISH001	5a	F	20-49	HPP	17.6	41.5	15.2	3.2	-18.6	9.8
	MISH002	3	F	>40**	HPP	7.2	39.1	14.3	3.2	-18.6	10.1
	MISH003	5a	F	20-49	HPP	7.2	38.9	14.2	3.2	-18.8	11.8
	MISH004	3	F	20-49	HPP	14.8	40.9	15.1	3.2	-19.0	11.2
	MISH005	4a	F	>50**	HPP	6.4	42.7	15.5	3.2	-18.8	11.2
	MISH006	3	M	>40**	HPP	7.8	40.0	14.6	3.2	-18.3	11.5
	MISH007	4a	M	20-49	HPP	7.1	40.7	14.8	3.2	-19.0	11.7
	MISH008	5a-5b	M	20-49	HPP	10.9	42.2	15.3	3.2	-18.9	9.0
	MISH009	3	M	>50**	HPP	8.3	42.3	15.0	3.3	-18.9	9.5
	MISH010	5a	F	>40**	HPP	11.5	41.8	15.3	3.2	-18.7	11.6
	MISH011	3	F	>30	HPP	10.6	41.3	15.1	3.2	-18.6	10.6
	MISH012	5a	F	20-39	HPP	8.9	38.7	14.2	3.2	-19.0	9.8
	MISH013	5b-6a	M	20-49	HPP	13.6	41.8	15.3	3.2	-18.4	10.1
	MISH014	5a-5b	F	20-29*	HPP	10.0	42.1	15.4	3.2	-19.4	6.7
	MISH015	3	M	20-29*	HPP	16.1	42.1	15.5	3.2	-19.0	11.0
	MISH016	3	F	>40**	HPP	7.1	37.9	13.8	3.2	-18.6	9.6
	MISH017	5a	M	>30	HPP	10.4	42.0	15.4	3.2	-18.7	9.9
	MISH018	4a	M 20-29*	HPP	3.9	5.5	1.9	3.3	-19.4	8.9
	MISH019	6a	M	>60**	HPP	15.5	41.7	15.2	3.2	-18.9	10.7
	MISH020	3	M	>30	HPP	4.3	32.5	11.9	3.2	-18.7	10.2
	MISH021	3	M	20-29*	HPP	14.0	41.3	15.3	3.2	-18.7	10.6
	MISH022	3	F	>30	HPP	12.5	42.1	15.3	3.2	-19.1	8.5
	MISH023	5a	F	>30	HPP	8.9	40.5	14.9	3.2	-18.8	10.2
	MISH024	5b	M	>40**	HPP	3.8	37.3	13.6	3.2	-18.8	8.6
	MISH025	4b	M	20-39	HPP	15.9	42.4	15.6	3.2	-18.6	9.9
	MISH026	3	F	20-29*	HPP	9.1	41.6	15.0	3.2	-19.0	9.6
	MISH027	5a	M	>40**	HPP	10.5	41.4	15.1	3.2	-19.0	10.6
	MISH028	4b	M	>40**	HPP	11.8	42.1	15.4	3.2	-18.5	10.6
	MISH029	5b	F	>50**	HPP	12.9	41.4	15.2	3.2	-18.5	9.7
	MISH030	5b	F	20-49	HPP	8.5	39.0	14.2	3.2	-17.8	11.3
	MISH031	4b	M	>40**	PP	5.5	39.5	14.2	3.3	-18.9	9.6
	MISH032	3	F	>30	HPP	17.1	41.2	15.2	3.2	-18.7	10.6
	MISH033	3	F	>30	HPP	14.5	41.9	15.4	3.2	-18.7	10.0
	MISH034	3	F	20-49	HPP	17.4	43.3	15.7	3.2	-18.2	9.7
	MISH035	3	F	20-29*	HPP	15.6	41.5	15.3	3.2	-18.7	8.5
	MISH036	3	F	20-49	HPP	4.0	40.5	14.7	3.2	-18.6	9.9
	MISH037	6a	F	20-49	HPP	11.0	41.6	15.3	3.2	-18.5	10.1
	MISH038	4a	F	>40**	HPP	14.0	42.2	15.5	3.2	-18.4	11.0
	MISH039	3	F	>30	HPP	16.4	42.3	15.5	3.2	-18.8	10.0
	MISH040	5b-6a	F	20-29*	HPP	15.2	43.0	15.7	3.2	-18.8	8.8
	MISH041	5a	M	20-49	HPP	12.0	47.5	13.7	4.0	-21.0	10.8
	MISH042	4a-4b	M	20-29*	HPP	10.6	41.7	15.3	3.2	-18.8	9.9
	MISH043	5b	F	20-29*	HPP	9.4	41.5	15.3	3.2	-18.8	12.5
	MISH044	5b	F	>40**	HPP	7.2	38.1	14.0	3.2	-19.0	11.3
	MISH045	5a	F	>30	HPP	15.9	42.7	15.7	3.2	-18.9	11.7
	MISH046	4a-4b	M	20-39	HPP	9.4	42.0	15.4	3.2	-19.0	8.8
	MISH047	3	M	20-39	HPP	6.0	38.4	14.2	3.2	-18.5	10.3
	MISH048	3	M	>30	HPP	5.0	36.9	13.6	3.2	-18.7	10.9
	MISH049	5a	M	>30	HPP	9.2	41.7	15.3	3.2	-19.2	10.6
	MISH050	3-4a	M	>30	HPP	13.8	42.3	15.5	3.2	-18.6	10.9
	MISH051	3	M	>30	HPP	5.7	40.3	14.8	3.2	-18.8	10.6
	MISH052	3	M	>30	HPP	14.3	42.0	15.5	3.2	-18.7	10.2
	MISH053	3	F	20-49	HPP	16.3	42.5	15.5	3.2	-18.9	9.4
	MISH054	4b	F	>30	HPP	9.8	40.9	15.0	3.2	-18.9	9.2

Table 3 -

 3 Results of carbon and nitrogen isotope analyses and collagen quality criteria of faunal samples. Key: Samples in italic fall out with van Klinken (1999) conservation criteria and are not considered in the discussion

	LABCode	Species	Anatomical element	Datation	Yield (%)	Carbon content (%)	Nitrogen content (%)	C/N	δ 13 C (‰)	δ 15 N (‰)
	MIS F01	Goat	Tibia	4-6	8.0	40.4	14.8	3.2	-19.0	5.7
	MIS F02	Equid	Mandible	4-6	2.4	33.4	12.5	3.1	-17.6	6.0
	MIS F03	Sheep	Radius	4-6	8.1	39.5	14.7	3.1	-21.0	5.5
	MIS F04	Pig	Tibia	4-6	12.0	40.2	14.9	3.2	-19.9	7.6
	MIS F05	Cattle	Radius	2-6	10.6	41.9	15.3	3.2	-20.5	5.1
	MIS F06	Chicken	Ulna	4-6	16.5	42.3	15.4	3.2	-19.6	10.1
	MIS F07	Sheep	Femur	2-3	5.3	38.9	14.3	3.2	-20.3	3.8
	MIS F08	Equid	Metatarsus	2-3	2.0	22.6	8.4	3.1	-21.9	5.9
	MIS F09	Goat	Radius	2-3	16.4	42.0	15.4	3.2	-19.4	4.2
	MIS F10	Deer	Metatarsus	2-3	7.0	39.4	14.5	3.2	-20.1	4.4
	MIS F11	Pig	Tibia	2-3	10.9	42.4	15.5	3.2	-20.0	6.9
	MIS F12	Chicken	Tibio-tarse	2-3	12.7	41.1	15.0	3.2	-19.1	10.1
	MIS F13	Goat	Radius	2-6	13.0	40.8	14.9	3.2	-19.4	6.7
	MIS F14	Sheep	Metacarpus	2-6	9.9	40.0	14.7	3.2	-20.2	5.9
	MIS F15	Sheep	Tibia	4-6	3.7	40.7	14.9	3.2	-19.5	7.5
	MIS F16	Cattle	Metatarsus	4-6	12.2	40.8	15.0	3.2	-19.0	8.6
	MIS F17	Sheep	Tibia	4-6	2.4	31.6	10.6	3.5	-19.8	8.1
	MIS F18	Equid	Metapod	4-6	3.0	26.9	10.2	3.1	-19.8	6.1
	MIS F19	Cattle	Tibia	2-6	3.7	31.0	11.4	3.2	-19.1	8.6
	MIS F20	Pig	Femur	2-6	10.8	39.3	14.3	3.2	-19.9	6.2
	MIS	Rabbit	Tibia	2-6	7.1	37.5	13.7	3.2	-20.9	3.7
	MIS F22	Equid	Radius	2-6	9.5	39.8	14.6	3.2	-19.0	6.2
	MIS F23	Cattle	Radius	2-6	10.5	39.8	14.5	3.2	-19.8	8.6
	MIS F24	Pig	Radius	2-6	9.5	38.3	14.0	3.2	-20.0	8.7
	MIS F25	Sheep	Tibia	2-6	2.6	30.6	11.1	3.2	-19.1	7.7
	MIS F26	Northern pike	Vertebrae	4-6	3.6	36.9	13.4	3.2	-21.1	8.7
	MIS F27	European perch	Vertebrae	4-6	-
	MIS F28	Mullet	Vertebrae	4-6	-
	MIS F29	Eel	Vertebrae	4-6	4.3	41.0	15.4	3.1	-21.3	10.8
	MIS F30	Donkey	Tibia	2-6	6.1	41.4	14.9	3.2	-20.7	6.4
	MIS F31	Deer	Coxal	2-6	12.3	40.9	15.0	3.2	-20.4	4.5
	MIS F32	Cattle	Mandible	2-6	7.8	38.2	14.1	3.2	-18.5	8.4
	MIS F33	Sheep	Tibia	2-6	8.3	35.0	12.9	3.2	-19.7	7.2
	MIS F34	Dog	Tibia	2-6	4.7	40.3	14.6	3.2	-18.4	9.4
	MIS F35	Sheep	Tibia	2-6	6.3	38.2	14.1	3.2	-20.1	8.9
	MIS F36	Chicken	Coracoide	2-6	15.1	40.7	14.9	3.2	-19.3	9.1
	MIS F37	Cattle	Tibia	2-6	8.8	40.1	14.6	3.2	-18.6	5.3
	MIS F38	Equid	Humerus	4-6	3.6	23.5	8.6	3.2	-21.9	7.6
	MIS F39	Pig	Tibia	4-6	13.3	41.4	14.9	3.2	-20.3	4.8
	MIS F40	Cattle	Radius	4-6	7.3	38.8	14.2	3.2	-19.1	7.4
	MIS F41	Cattle	Tibia	2-3	2.1	19.4	7.2	3.2	-19.8	8.1
	MIS F42	Cattle	Femur	2-3	7.1	40.1	14.6	3.2	-20.0	4.9
	MIS F43	Pig	Ulna	2-3	10.8	41.2	15.0	3.2	-19.9	6.5
	MIS F44	Donkey	Radius	2-3	7.6	40.0	14.6	3.2	-19.8	7.6
	MIS F45	Sheep	Tibia	2-3	4.6	40.2	14.5	3.2	-20.0	5.9
	MIS F46	Cattle	Femur	4-6	11.5	40.6	14.9	3.2	-20.6	4.1
	MIS F47	Mullet	Vertabrae	4-6	3.6	41.7	15.1	3.2	-11.4	15.9
	MIS F48	Northern pike	Vertabrae	4-6	3.5	42.1	15.4	3.2	-24.6	8.7
	MIS F49	Duck	Humerus	4-6	16.3	41.8	14.7	3.3	-23.6	7.8
	MIS F50	Sheep	Ulna	4-6	13.8	42.1	15.3	3.2	-20.7	5.4
	MIS F51	Eel	Vertabrae	4-6	7.1	41.6	15.3	3.2	-24.4	7.8
	MIS F52	Cattle	Metatarsus	4-6	9.7	39.4	14.5	3.2	-18.9	9.9
	MIS F53	Cattle	Metacarpus	4-6	2.3	28.9	9.7	3.5	-19.8	8.8
	MIS F54	Cattle	Mandible	4-6	5.9	37.9	13.8	3.2	-19.5	8.1
	MIS F55	Pig	Tibia	4-6	4.4	39.4	14.4	3.2	-20.1	6.2

Table 4 -

 4 Summary of the  13 C and  15 N values of the different faunal species

					 13 C (‰)			 15 N (‰)
		N	Min	Max	Median [IIQ] a	Min	Max	Median [IIQ] a
	Duck	1	-23.6			7.8
	Eel	2	-24.4	-21.3		7.8	10.8
	Northern pike	2	-24.6	-21.1		8.7	8.7
	Mullet	1	-11.4			15.9
	Goose	1	-18.8			7.6
	Toad	1	-19.6			7.3
	Dog	1	-18.4			9.4
	Rabbit	1	-20.9			3.7
	Deer	2	-20.4	-20.1		4.4	4.5
	Equid	2	-19.0	-17.6		6.0	6.2
	Donkey	2	-20.7	-19.8		6.4	7.6
	Goat	4	-20.8	-19.0		4.2	10.3
	Chicken	6	-19.6	-18.2	-19.1	7.8	10.8	10.8
	Pig	12	-20.6	-19.1	-19.9 [-20.1/-19.8]	4.8	8.7	6.6 [6.2/7.1]
	Cattle	12	-20.6	-18.5	-19.1 [-19.8/-18.9]	4.1	10.1	8.3[5.3/8.6]
	Terrestrial	3	-20.6	-20.0		4.1	5.1
	Lagoon	9	-19.8	-18.5	-19.0	5.3	10.1	8.6
	Sheep	13	-21.0	-19.1	-20.2 [-20.7/-20.0]	3.8	8.9	6.5 [5.5/7.7]
	Terrestrial	8	-21.0	-20.2	-20.7	3.8	7.8	5.5
	Lagoon	6	-20.1	-19.1	-19.9	5.9	8.9	7.6
	Domestic triad c 41	-21.0	-18.5	-19.9 [-20.2/-19.4]	3.8	10.3	6.7 [5.5/8.1]
	Phase 2-3	13	-20.7	-19.0	-20.0 [-20.2/-19.5]	3.8	10.1	6.5 [4.9/6.9]
	Phase 4-6	16	-21.0	-18.9	-19.9 [-20.6/-19.4]	4.1	10.3	7.0 [5.5/8.2]
	TOTAL	63	-24.6	-11.4	-19.1 [-20.3/-19.1]	3.7	15.9	7.5 [5.8/8.6]

a IIQ : first/third quartiles, median is provided when n≥5 and IIQ are provided when n≥10 b Domestic triad : cattle, sheep and goat, pig

Table 6 -

 6 Summary of the isotopic values for humans according to chronological phases and biological criteria: sex and age at death IIQ : first/third quartiles, median is provided when n≥5 and IIQ are provided when n≥10 b Statistical parameters are provided when n≥20

						 13 C (‰)	 15 N (‰)
			N	Min	Max	Median [IIQ] a	Mean±SD b Min Max Median [IIQ] a	Mean±SD b
	Chronological phases
	Phase 2	1	-18.8			10.6
	Phase 3	58 -19.5 -18.2 -18.7 [-18.9/-18.5] -18.7±0.3 8.1 11.5	9.9 [9.3/10.4]	9.8±0.8
	Phase 3/4	11 -18.8 -18.5 -18.6 [-18.8/-18.6]	9.0 11.7 10.3|9.6/10.9]
	to 6	Phase 4 Phase 4/5	25 -19.2 -18.4 -18.8 [-18.9/-18.6] -18.8±0.2 7.7 12.1 10.6 [9.8/11.1] 1 -19.2 10.9	10.4±1.1
	4 Phases	Phase 5 Phase 5/6 Phase 6a	44 -20.1 -17.8 -18.9 [-19.0/-18.7] -18.8±0.4 6.7 13.1 10.6 [9.9/11.3] 2 -18.8 -18.4 8.8 10.1 4 -18.9 -18.5 9.9 11.9	10.4±1.2
		Total	76 -20.1 -17.8 -18.8 [-19.0/-18.6] -18.3±0.3 6.7 13.1 10.6 [9.9/11.2]	10.4±1.2
	Biological criteria: Sex
		Phase 3	29 -19.3 -18.2 -18.7 [-18.8/-18.5] -18.7±0.2 8.4 11.0	9.9 [9.6/10.4]	9.9±0.6
		Phase 3/4	8	-18.8 -18.5	-18.7	9.0 11.3	10.2
		Phase 4	16 -19.2 -18.3 -18.8 [-18.9/-18.7]	8.3 11.9 10.4 [9.5/10.9]
	Male	Phase 4/5 Phase 5	1 18 -19.6 -18.3 -18.9 [-19.0/-18.6] -18.8	8.8 6.7 11.4 10.3 [9.3/10.7]
		Phase 5/6	1	-18.9			9.9
		Phase 6a	2	-19.0 -18.8		11.7 11.7
		Total	75 -19.6 -18.2 -18.8 [-18.9/-18.6] -18.8±0.3 7.7 12.1 10.3 [9.6/10.8]	10.2±0.9
		Phase 2	1	-18.8			10.6
		Phase 3	29 -19.5 -18.2 -18.7 [-18.9/-18.6] -18.7±0.3 8.1 11.2	9.7 [9.1/10.1]	9.7±0.8
	Female	Phase 3/4 Phase 4 Phase 5	3 9 26 -20.1 -17.8 -18.9 [-19.0/-18.6] -18.8±0.4 7.7 13.1 10.7 [10.1/11.5] 10.8±1.1 -18.8 -18.6 9.7 12.1 -19.2 -18.3 -18.8 [-18.9/-18.4] 9.2 12.1 11.0 [10.8/11.2]
		Phase 5/6	1	-18.9			10.1
		Phase 6a	2	-18.5 -18.5		10.1 10.6
		Total	71 -20.1 -17.8 -18.8 [-18.9/-18.6] -18.8±0.3 6.7 13.1 10.1 [9.5/11.0]	10.2±1.1
	Biological criteria: Age
		Phase 3	14 -19.0 -18.3 -18.7 [-18.8/-18.5]	8.5 11.0	9.5 [9.1/10.3]
		Phase 3/4	2	-18.6 -18.5		10.8 12.1
	20-39	Phase 4 Phase 5/6	4 1	-18.8 -18.3 -18.9		8.5 10.4 10.1
		Phase 5	9	-19.4 -18.5	-18.8	6.7 13.1	9.9
		Total	29 -19.4 -18.3 -18.8 [-18.9/-18.6] -18.7±0.2 6.7 13.1	9.8 [9.1/10.4]	9.8±1.2
		Phase 3	10 -19.2 -18.4 -18.8 [-18.8/-18.6]	8.4 10.4	9.6 [9.5/10.1]
		Phase 4	11 -19.1 -18.3 -18.8 [-18.9/-18.6]	8.6 11.5 10.9 [10.0/11.1]
	> 40	Phase 4/5 Phase 5	1 10 -19.6 -18.4 -18.9 [-19.0/-18.6] -18.8	8.8 8.3 11.6 10.6 [10.4/11.2]
		Phase 5/6	1	-18.9			9.9
		Phase 6a	1	-18.8			11.7
		Total	35 -19.6 -18.3 -18.8 [-18.9/-18.6] -18.8±0.3 8.3 12.1 10.4 [9.6/11.0]	10.3±0.9
		Total	146 -20.2 -17.8 -18.8 [-18.9/-18.6] -18.8±0.3 6.7 13.1 10.2 [9.6/10.8]	10.2±1.0

a

ACKNOWLEDGEMENTS

The authors want to thank Ian Newton (UCT) want to thank Ian Newton (UCT) for technical support with the mass spectrometers. O. Maufras as well as the two anonymous reviewers are gratefully acknowledged for commenting and improving this manuscript. S. Cravinho is acknowledged for the determination and sampling of fish remains. This work has been financially supported by the Louis Bonduelle Foundation and the Nestlé France Foundation in the form of two Research Awards received

by LM in 2016. The isotope analyses were financed by the Institut National de Recherches Archéologiques Préventives-Méditerranée.

CONFLICT OF INTEREST

The authors have no conflict of interest to declare.


Yasmina Bouizem

An Approach for Energy-Efficient, Fault Tolerant FaaS Platforms

Recent years have seen the emergence of serverless computing and, in particular, the "Function as a Service" (FaaS) paradigm, which lets users run arbitrary functions without being concerned about operational issues.

This paper describes several research questions about how to design better Function-as-a-Service platforms in term of performance, fault tolerance and energy consumption. I have started tackling these open questions, starting with an evaluation of Kubernetesnative FaaS frameworks.

INTRODUCTION

The FaaS model promises reduced operational costs, reduced packaging and deployment complexity, high availability, and automated elasticity [START_REF] Lloyd | Serverless computing: An investigation of factors influencing microservice performance[END_REF], and has been applied in diverse domains, such as IoT, machine learning inference, and image processing. All the main cloud providers have embraced the FaaS model with offerings such as AWS Lambda [START_REF]AWS Lambda -Serverless Compute -Amazon Web Services[END_REF], Google Cloud Functions [START_REF]Google Cloud Functions[END_REF], and Azure Functions [START_REF]Azure Functions-Serverless Architecture -Microsoft Azure[END_REF]. A growing number of open-source platforms enable implementing FaaS systems on private clouds [START_REF]Fission -Serverless functions for kubernetes[END_REF][START_REF]What is Kubeless[END_REF][START_REF] Ellis | OpenFaaS[END_REF]. Nevertheless, current FaaS platforms are immature and cannot effectively meet the needs of their stakeholders, that is, the users that deploy applications, and the provider that owns and operates the platform. The aim of this work is to develop an automated resource management solution for FaaS platforms that satisfies the performance and availability requirements of users, while reducing the energy consumption for the provider.

The paper is structured as follows. Section 2 presents a survey of related reseach in serverless computing. Section 3 describes challenges and gaps identified in FaaS frameworks. Section 4 proposes an approach to improve FaaS platforms. Finally, in section 5, a conclusion is drawn.

BACKGROUND AND RELATED WORK

Recently several works related to the FaaS paradigm have been proposed.

In [START_REF] Lee | Evaluation of Production Serverless Computing Environments[END_REF] authors evaluated serverless computing environments with respect to concurrent invocations by deploying a series of functions for large distributed data processing. They compared the performance of CPU, memory and disk-intensive functions and measured throughput to understand the function behaviour on serverless computing environments. [START_REF] Lloyd | Serverless computing: An investigation of factors influencing microservice performance[END_REF] focused on identifying factors which influence the performance of microservices deployed on serverless platforms. The authors investigated hosting implications related to infrastructure elasticity, load balancing, provisioning variation, infrastructure retention, and memory reservation size. [START_REF] Mcgrath | Serverless computing: Design, implementation, and performance[END_REF] proposed a novel prototype of a queuing scheme implemented in. NET, deployed in Microsoft Azure, and utilizing Windows containers as function execution environments. The authors proposed metrics, such as throughput, to evaluate the performance of the proposed prototype as well as the following serverless platforms: AWS Lambda, Azure Functions, Google Cloud Functions, and Apache OpenWhisk. [START_REF] Shillaker | A Provider-Friendly Serverless Framework for Latency-Critical Applications[END_REF] evaluated OpenWhisk performance with different numbers of concurrent functions. The author plans to investigate isolation within the language runtime itself and to build a new multi-tenant serverelss language runtime to reduce latency seen by users while improving resource efficiency for the provider. [START_REF] Istemi Ekin Akkus | SAND: towards highperformance serverless computing[END_REF] introduced a novel, high-performance serverless platform, SAND, that provides lower latency, better resource efficiency and more elasticity than existing serverless platforms. The authors implemented and deployed a complete SAND system. Their results show that SAND outperforms state-of-the-art serverless platforms such as OpenWhisk. [START_REF] Baldini | Serverless computing: Current trends and open problems[END_REF] identified key characteristics and use cases for FaaS and described technical challenges and open problems. [START_REF] Lynn | A Preliminary Review of Enterprise Serverless Cloud Computing (Function-as-a-Service) Platforms[END_REF] presented the major enterprise serverless cloud computing platforms and a comparison based on general and high-level technical features such as scalability, log management, orchestration, dependencies and maximum number of functions. [START_REF] Stein | The Serverless Scheduling Problem and NOAH[END_REF] analysed the current serverless scheduling problem and introduced the new allocation heuristic NOAH to solve it. [START_REF] Erwin Van Eyk | A SPEC RG cloud group's vision on the performance challenges of FaaS cloud architectures[END_REF] identified some performance challenges that arise specifically in the FaaS model.

There are further challenges identified in related papers: scheduling policies, cold starts, session management, code and data locality, load balancing and resource allocation among others [START_REF] Adzic | Serverless computing: economic and architectural impact[END_REF][START_REF] Buyya | A Manifesto for Future Generation Cloud Computing: Research Directions for the Next Decade[END_REF][START_REF] Hendrickson | Serverless computation with openlambda[END_REF].

The focus so far has been on analysing the benefits and limitations of current serverless technology, identifying factors which influence serverless computing performance, and trying to come up with solutions to improve performance. There is currently no work that addresses performance concerns combined with availability and energy efficiency concerns in FaaS. In this work, we are going to tackle this challenge and study the trade-offs between the three parameters.

CHALLENGES FOR FAAS FRAMEWORKS

Despite the attractive features promised by FaaS, current platforms tend to be immature and suffer from multiple limitations with regards to resource management. First, the platforms provide no support for managing the quality of service experienced by FaaS user. For instance, users have no influence on the latency of function execution. Second, the platforms provide no fault-tolerance mechanisms beyond a basic retry mechanism that brings up a new container when a failure is detected. Implementing further mechanisms, such as active or semi-active replication, would allow greater flexibility in the way that performance and availability requirements are managed. Third, the platforms do not take into account energy savings in resource management decisions. Finally, the platforms provide no integrated management system that takes into account the objectives of users and the provider in a coordinated manner. For example, most platforms offer auto-scaling capabilities, but these focus on optimizing the scaling of individual functions and applications.

To address the open issues discussed before, we focus on FaaS frameworks based on Kubernetes [START_REF]Kubernetes[END_REF] and deployed on private infrastructures, following the architecture shown in Figure 1. Our resource management solution will be implemented in the FaaS framework layer, exploiting the configurability and extensibility of Kubernetes. In particular, the solution will allow FaaS users to express their requirements regarding performance and availability, for example, through defining different levels of quality of function execution. The solution will then take into account these requirements along with information on the current state of the system in order to take appropriate resource management decisions. Examples of such decisions include determining the placement of functions on containers and nodes, selecting appropriate replication mechanisms, dynamically scaling functions as well as reacting to failures and workload changes. Making these decisions will be based on performance and energy consumption models which will be generated using profiling and historical information [START_REF] Dib | SLAbased PaaS profit optimization[END_REF][START_REF] Parlavantzas | Cost-Effective Reconfiguration for Multi-Cloud Applications[END_REF].

As a first step towards developing the solution, we are evaluating three popular open source FaaS frameworks (Kubeless [START_REF]What is Kubeless[END_REF], Fission [START_REF]Fission -Serverless functions for kubernetes[END_REF] and OpenFaaS [START_REF] Ellis | OpenFaaS[END_REF]), all based on Kubernetes, which allow deploying serverless on private infrastructures without any form of vendor lock-in. In particular, we are evaluating these frameworks with respect to their performance, fault-tolerance, and energy consumption properties as well as their extensibility; the goal is to select the most appropriate framework for hosting our resource management solution.

CONCLUSION

The emerging FaaS model is the latest step in the long trend towards higher levels of abstraction in cloud programming models. The model enables developers to write stateless code without worrying about provisioning, configuring, and managing servers. However, current FaaS platforms provide little support for managing performance, availability, and energy efficiency requirements, which reduces the value of the platforms, and impedes their adoption in private clouds.

This paper highlighted the key challenges in addressing this problem and discussed related work in industry and research. The paper also gave an outline of our approach and the first steps in developing a solution to the problem. We hope that our solution can help bring the many benefits of serverless computing to private clouds.

Figure 1 :

 1 Figure 1: Kuberetes native FaaS frameworks architecture

ACKNOWLEDGMENTS

I would like to thank Christine Morin, Djawida Dib and Nikos Parlavantzas for their valuable comments and helpful suggestions.