Unité de Taphonomie Médico-Légale

This review offers the first synthesis of the research on mixed-species groupings of arthropods and highlights the behavioral and evolutionary questions raised by such behavior. Mixed-species groups are commonly found in mammals and birds. Such groups are also observed in a large range of arthropod taxa independent of their level of sociality. Several examples are presented to highlight the mechanisms underlying such groupings, particularly the evidence for phylogenetic proximity between members that promotes cross-species recognition. The advantages offered by such aggregates are described and discussed. These advantages can be attributed to the increase in group size and could be identical to those of nonmixed groupings, but competition-cooperation dynamics might also be involved, and such effects may differ between homo- and heterospecific groups. We discuss three extreme cases of interspecific recognition that are likely involved in mixed-species groups as vectors for cross-species aggregation: tolerance behavior between two social species, one-way mechanism in which one species is attractive to others and two-way mechanism of mutual attraction. As shown in this review, the study of mixed-species groups offers biologists an interesting way to explore the frontiers of cooperation-competition, including the process of sympatric speciation.

The use of insects as indicators of post-mortem displacement is discussed in many texts, courses and TV shows, and several studies addressing this issue have been published. Although the concept is widely cited, it is poorly understood, and only a few forensic cases have successfully applied such a method. The use of necrophagous insects as evidence of cadaver relocation actually involves a wide range of biological aspects. Distribution, microhabitat, phenology, behavioral ecology, and molecular analysis are among the research areas associated with this topic. This article provides the first review of the current knowledge and addresses the potential and limitations of different methods to evaluate their applicability. This work reveals numerous weaknesses and erroneous beliefs as well as many possibilities and research opportunities.

OBJECTIVES: Cementochronology based on annual deposition of acellular cementum is acknowledged for its superior performance for estimating age-at-death but is also disregarded because of its suspicious effectiveness. This article aims to provide a standardized framework for the validation of the technique and to define and test cementochronology's performance and limitations. MATERIALS AND METHODS: To determine the boundaries of the cementum aging technique, we applied a certified protocol on a sample of 200 healthy canines from individuals of known age, sex, postmortem, and inhumation intervals from anthropological and anatomical collections. We scored readability and preservation of cementum and measured the agreement between estimates, i.e., the precision, and assessed the quality of the accordance between estimates and chronological age, i.e., the accuracy. To investigate the applicability on ancient material, 200 additional canines extracted from archeological assemblages were included. Accuracy and precision were analyzed for each age group in considering postmortem intervals and taphonomical conditions. RESULTS: A strong correlation was found between chronological age and estimates (r = .927; p = .000) but results reveal an association between readability of incremental lines and chronological age (p < .05) and a notable difference in both precision and accuracy between individuals under and over 50 years. Results also demonstrate that taphonomy can be a serious obstacle increasing imprecision by a factor of three. DISCUSSION: Improperly adopted, cementochronology can lead to precise but inaccurate estimations. If methodological, physiological, and taphonomical factors are taken into account, then, and only then, cementochronology will serve as a versatile and powerful tool for age-at-death estimation.

Necrophagous flies breeding on carcasses face high selection pressures and therefore provide interesting opportunities to study social adaptations. We postulated that gregariousness in necrophagous blow fly larvae is an adaptive response to the environmental constraints of fresh carcasses. Cooperation is indeed believed to be key to the global success of social species. To test this idea, the development of Lucilia sericata (Diptera: Calliphoridae) larvae growing on low- or high-digestibility food substrate (control or trypsin-added ground beef muscle, respectively) at different larval densities was monitored. Results showed that larvae developed faster and had decreased mortality at high than low larval density. Furthermore, aggregation had no deleterious effect on the morphological characteristics (e.g. size) of postfeeding larvae and adult flies. We concluded that increased density positively affected population fitness, which is a conclusion consistent with the predictions of the Allee effect. Compared with those fed on regular food, larvae fed on high-digestibility food had reduced mortality and faster development on average. From these results, we postulated that collective exodigestion might be an adaptive response allowing blow flies to colonize fresh carcasses before the arrival of other insects and the multiplication of microbes. This hypothesis is consistent with the idea that cooperation may enable species to expand their niches.

Abstract Due to the ephemeral nature of carcasses they grow on, necrophagous blowfly larvae should minimize the time spent on the cadaver. This could be achieved by moving to high‐temperature areas. On that basis, we theorized that larvae placed in a heterogeneous thermal environment would move to the higher temperature that speed up their development. This study was designed to (1) test the ability of necrophagous larvae to orientate in a heterogeneous thermal environment, and (2) compare the temperatures selected by the larvae of three common blowfly species: Lucilia sericata (Meigen), Calliphora vomitoria (L.) and Calliphora vicina (Robineau‐Desvoidy). For this purpose, we designed a setup we named Thermograde. It consists of a food‐supplied linear thermal gradient that allows larvae to move, feed, and grow in close‐to‐real conditions, and to choose to stay at a given temperature. For each species and replication, 80 young third instars were placed on the thermal gradient. The location of larvae was observed after 19 h, with fifteen replications per species. The larvae of each species formed aggregations that were always located at the same temperatures, which were highly species‐specific: 33.3 ± 1.52 °C for L. sericata , 29.6 ± 1.63 °C for C. vomitoria , and 22.4 ± 1.55 °C for C. vicina . According to the literature, these value allows a fast development of the larvae, but not to reach the maximum development rate. As control experiments clearly demonstrate that larval distribution was not due to differences in food quality, we hypothesized that the local temperature selection by larvae may result from a trade‐off between development quality and duration. Indeed, temperature controls not only the development rate of the larvae, but also the quality of their growth and survival rate. Finally, results raise questions regarding the way larvae moved on the gradient and located their preferential temperature.

Necrophagous insects are mostly known through forensic entomology. Indeed, experimental data investigating the effect of temperature on larval development underlies post-mortem interval estimations. However, such developmental studies rarely considered the behavior of maggots. In contrast, previous results supposed that calliphoridae larvae use behavioral strategies to optimize their development on carcasses. To test this idea, we analyzed the trade-off between thermal regulation (individual thermal preferences) and social behavior (aggregation) in Lucilia sericata larvae. The first set of experiments analyzed the behavior of third instars in response to thermal changes in their environment. The results demonstrated a clear thermoregulation behavior, supporting the assumption that larvae continuously move to reach a suitable internal temperature. The second set of experiments focused on the trade-off between thermal optimization and aggregation. The results showed a constant search for congeners and an attractiveness of aggregates, sometimes to the detriment of thermal optimization. Together, these results demonstrate a balance between behavioral thermoregulation and social strategies, two significant mechanisms for developmental optimization in necrophagous larvae. In conclusion, these findings highlights unexpected (social) strategies to cope with ephemeral resource and high selection pressure. They also raise important questions for forensic entomology.

To date, the study of collective behaviour has mainly focused on intraspecific situations: the collective decision-making of mixed-species groups involving interspecific aggregation-segregation has received little attention. Here, we show that, in both conspecific and heterospecific groups, the larvae of two species (Lucilia sericata and Calliphora vomitoria, calliphorid carrion-feeding flies) were able to make a collective choice. In all groups, the choice was made within a few minutes and persisted throughout the period of the experiment. The monitoring of a focal individual within a group showed that these aggregations were governed by attractive and retentive effects of the group. Furthermore, the similarity observed between the conspecific and heterospecific groups suggested the existence of shared aggregation signals. The group size was found to have a stronger influence than the species of necrophagous larvae. These results should be viewed in relation to the well-known correlation between group size and heat generation. This study provides the first experimental examination of the dynamics of collective decision-making in mixed-species groups of invertebrates, contributing to our understanding of the cooperation-competition phenomenon in animal social groups.

Dental cementum attracts considerable attention and interest from biological anthropologists because it offers direct access to a chronological record, like a biological black box. A black box is defined as a system that systematically archives events, but the term also refers to a complex organization whose internal workings are not readily understood. Both definitions are well suited to this fascinating dental tissue. Dental Cementum in Anthropology, edited by Naji, Rendu and Gourichon, com...

ABSTRACT Collective decisions have been extensively studied in arthropods, but they remain poorly understood in heterospecific groups. This study was designed to (1) assess the collective behaviours of blow fly larvae (Diptera: Calliphoridae) in groups varying in density and species composition, and (2) relate them to the costs and benefits of aggregating on fresh or decomposed food. First, experiments testing conspecific groups of Lucilia sericata and Calliphora vicina larvae, two species feeding at the same time on fresh carcasses, demonstrated decreases in growth and survival on rotten beef liver compared with fresh liver. However, mixing species together reduced this adverse impact of decomposition by increasing the mass of emerged adults. Second, larval groups were observed in binary choice tests between fresh and rotten liver (i.e. optimal and sub-optimal food sources). The results showed that larvae interacted with each other and that these interactions influenced their food preferences. We observed that (1) larvae were able to collectively choose the optimal food, (2) their choice accuracy increased with larval density and (3) the presence of another species induced a reversal in larval preference towards rotten food. These results highlight the ubiquity of collective decision properties in gregarious insects. They also reveal an unexpected effect of interspecific association, suggesting the colonization of new resources through a developmental niche construction.

We report a case of fatal intoxication from 1,4-butanediol (1,4-BD), which was ingested by a young and "naïve" gamma-hydroxybutyrate (GHB) consumer during a party with the co-ingestion of alcohol, cannabis, and methylene-dioxy-methamphetamine. The following drug concentrations were found using gas chromatography coupled with mass spectrometry on autopsy samples and on a cup and a glass found at the scene: 20,350 mg/L (bottle) for 1,4-BD; 1020 mg/L (femoral blood), 3380 mg/L (cardiac blood), 47,280 mg/L (gastric content), and 570 mg/L (vitreous humor) for GHB. The concentration of GHB is difficult to interpret in forensic cases due to the possibility of an endogenous production of GHB. The variable tolerance of the user may also modify the peri- and postmortem GHB concentrations. This case underscores the need to have many different sources of toxicology samples analyzed to avoid the hypothesis of endogenous production of GHB.

Abstract The study of dental morphology can be a very useful tool to understand the origin and evolution of Neanderthals in Europe during the Middle Pleistocene (MP). At present, the earliest evidence, ca. 430 ka, of a pre-Neanderthal population in Europe is the hominin sample from Atapuerca-Sima de los Huesos (SH) that present clear dental affinities with Neanderthals while other penecontemporaneous populations, such as Arago or Mala Balanica, exhibit less Neanderthal traits. We present the morphometric study of the external and internal dental structures of eleven hominin dental remains recovered from the MP, ca. 240 ka, French site of Biache-Saint-Vaast (BSV). Our analyses place the BSV hominins within the MP group, together with SH, Fontana Ranuccio, Visogliano, Steinheim or Montmaurin, that show greater morphological affinities with Neanderthals. Moreover, we identified interpopulation variability in the expression of the enamel thickness trait, with BSV hominins sharing the unique combination of thin and thick pattern in the premolars and molars with the SH population. These results further support the coexistence of two or more populations in Europe during the MP that reflect the population and settlement of human groups suggested by the Central Area of Dispersals of Eurasia (CADE) and sink and source model.

It has been repeatedly acknowledged that age-at-death estimation based on dental cementum represents a partial and time-consuming method that hinders adoption of this histological approach. User-friendly micrograph analysis represents a growing request of cementochronology. This article evaluates the feasibility of using a module to accurately quantify cementum deposits and compares the module's performance to that of a human expert. On a dental collection (n = 200) of known-age individuals, precision and accuracy of estimates performed by a developed program (101 count/tooth; n = 20,200 counts) were compared to counts performed manually (5 counts/tooth; n = 975 counts). Reliability of the software and agreement between the two approaches were assessed by intraclass correlation coefficient and Bland Altman analysis. The automated module produced reliable and reproducible counts with a higher global precision than the human expert. Although the software is slightly more precise, it shows higher sensitivity to taphonomic damages and does not avoid the trajectory effect described for age-at-death estimation in adults. Likewise, for human counts, global accuracy is acceptable, but underestimations increase with age. The quantification of the agreement between the two approaches shows a minor bias, and 94% of individuals fall within the intervals of agreement. Automation gives an impression of objectivity even though the region of interest, profile position and parameters are defined manually. The automated system may represent a time-saving module that can allow an increase in sample size, which is particularly stimulating for population-based studies.

The use of insects as indicators of postmortem displacement is discussed in many text, courses and TV shows, and several studies addressing this issue have been published. However, the concept is widely cited but poorly understood, and only a few forensic cases have successfully applied such a method. Surprisingly, this question has never be taken into account entirely as a cross-disciplinary theme. The use of necrophagous insects as evidence of cadaver relocation actually involves a wide range of data on their biology: distribution areas, microhabitats, phenology, behavioral ecology and molecular analysis are among the research areas linked to this problem. This article reviews for the first time the current knowledge on these questions and analysze the possibilities/limitations of each method to evaluate their feasibility. This analysis reveals numerous weaknesses and mistaken beliefs but also many concrete possibilities and research opportunities.

RésuméLorsqu’un animal meurt, son cadavre forme un écosystème local instable et éphémère où différentes communautés d’insectes nécrophages vont se nourrir. Cette étude a pour but de caractériser les relations entre deux familles fréquentes en contextes médico-légal : les Diptères Calliphoridae et les Coléoptères Dermestidae. Des expériences de choix binaire (olfactomètres en T) et de prédation des Dermestes sur les larves de Diptères ont constitué le 1er axe de notre étude. Il en ressort que l’espèce D. maculatus (adultes et larves) n’exerce qu’une très faible prédation sur les larves de L. sericata. En absence de nourriture, les Dermestes sont néanmoins capables de prédater les pupes de L. sericata, et donc de faire disparaitre ces traces particulièrement importantes en entomologie médico-légale et en archéo-entomologie. Le second axe s’est focalisé sur les relations de compétition et d’agrégation entre D. maculatus et D. haemorrhoidalis. Les résultats obtenus n’ont pas mis en évidence de mécanismes de compétition ou d’exclusion entre ces deux espèces pourtant amenées à fréquenter simultanément le même habitat et à exploiter les mêmes ressources. Placées en condition de choix binaire (2 spots identiques), les 2 espèces s’agrègent ensemble. Mais le développement conjoint de ces 2 espèces sur une seule source de nourriture non limitante entraine une baisse significative du taux de survie chez les deux espèces. Au vu de ces résultats, nous avons conclu à la possibilité d’une coexistence de ces différentes espèces (L. sericata, D. maculatus et D. haemorrhoidalis) sur un cadavre.

The estimation of the postmortem interval for skeletal remains is a crucial aspect of forensic anthropology. This paper illustrates the importance of radiocarbon analysis for establishing medico-legal significance and supporting forensic identification, through the analysis of three case studies for which the years of both birth and death were investigated. In Audresselles, Northern France, a partial skull was discovered with no contextual information or identity. Radiocarbon dating yielded an average calibrated calendar age of 4232 BCE (92.5% probability), indicating significant archaeological value but no forensic relevance. In the second case, skeletal remains were found in the flooded underground of a historical fort at Wimereux, Northern France, also with no identity. Radiocarbon dating based on the bomb-pulse curve indicated a calibrated date of death in 1962 CE (37.3% probability) or 1974-1975 CE (58.1% probability), both surpassing the French statute of limitations. Lastly, a skeleton with a suspected identity was discovered near Valenciennes, Northern France, and various biological tissues underwent radiocarbon dating. A bone sample suggested a calibrated date of death of 1998-2002 CE (84.6% probability), differing from a hair sample (2013-2018 CE, 83.3% probability) because of the slower bone tissue remodeling process. DNA analysis confirmed the person's identity, reported missing a decade prior to the discovery of the remains, following the alignment of the radiocarbon results with the individual's year of birth based on dental tissues and year of death. These case studies reveal that traditional radiocarbon dating and bomb-pulse dating are essential tools for estimating the postmortem interval, providing mutual benefits for archaeologists, forensic anthropologists, and the criminal justice system. Key points: Traditional radiocarbon dating and bomb-pulse dating are essential tools to establish the archaeological relevance or medico-legal significance of human skeletal remains.Bomb-pulse dating enables assessment of an individual's years of birth and death.Bomb-pulse dating helps to narrow down the pool of candidates for identification.Radiocarbon analysis provides mutual benefits for archaeologists, forensic anthropologists, and the criminal justice system.

Proteomics is continually being applied to a wider range of applications, now including the analysis of archaeological samples and anatomical specimens, particularly collagen-containing tissues such as bones and teeth. Here, we present the application of a chemical digestion-based proteomics sample preparation protocol to the analysis of fresh, anatomical, and archaeological samples. We describe and discuss two protocols: one that uses hydroxylamine as an additional step of the proteomic workflow, applied to the insoluble fraction, and another that applies hydroxylamine directly on demineralized bones and teeth. We demonstrate the additional information that can be extracted using both protocols, including an increase in the sequence coverage and number of peptides detected in modern and archaeological samples and an increase in the number of proteins identified in archaeological samples. By targeting research related to collagens or extracellular matrix proteins, the use of this protocol will open new insights, considering both fresh and ancient mineralized samples.

After death, diagenesis takes place. Numerous processes occur concomitantly, which makes it difficult to identify the diagenetic processes. The diagenetic processes refer to all processes (chemical or physical) that modify the skeletal remains. These processes are highly variable depending on the environmental factors (weather, temperature, age, sex, etc.), especially in the early stages. Numerous studies have evaluated bone diagenetic processes over long timescales (~millions of years), but fewer have been done over short timescales (between days and thousands of years). The objective of the study is to assess the early stages of diagenetic processes by Raman microspectroscopy over 12 months. The mineral and organic matrix modifications are monitored through physicochemical parameters. Ribs from six humans were buried in soil. The modifications of bone composition were followed by Raman spectroscopy each month. The decrease in the mineral/organic ratio and carbonate type-B content and the increase in crystallinity reveal that minerals undergo dissolution-recrystallization. The decrease in collagen cross-linking indicates that collagen hydrolysis induces the fragmentation of collagen fibres over 12 months.

L’estimation de l’âge au décès de sujets adultes découverts en contexte médico-légal ou archéologique est un sujet fondamental. La cémentochronologie, fondée sur le dépôt annuel de cément, est une technique parmi les plus performantes dont l’exactitude est appréciée dans de nombreuses publications. Cependant, le manque de standardisation ralentit l’adoption de cette méthode et freine l’étude de la précision qui demeure méconnue tout comme l’impact des conditions taphonomiques. L’objectif de ce travail est de mesurer la concordance des estimations, donc la précision, puis d’évaluer l’exactitude, donc la qualité de l’accord entre l’âge estimé et l’âge chronologique, en appliquant un protocole standardisé pour s’affranchir des biais inhérents à la préparation. L’étude porte sur 2 000 lames histologiques réalisées à partir de 400 canines. Deux cents canines sont issues de collections de référence dont l’âge, le sexe, l’intervalle post mortem et la durée d’inhumation des sujets sont connus. Afin d’étudier l’applicabilité de la méthode à du matériel ancien, 200 canines extraites de sujets archéologiques datés entre les XII e et XVIII e siècles sont intégrées à l’étude. Les résultats démontrent que l’analyse cémentochronologique peut permettre une estimation fiable de l’âge au décès mais révèlent également une diminution significative de la lisibilité des dépôts cémentaires avec l’âge et une moindre efficacité pour les sujets de plus de 50 ans.

d'Anthropologie s'engagent pour une science

Abstract Metastatic bone disease significantly impacts cancer‐related morbidity and mortality nowadays. Herein, we present an adult individual, probably a female, with multiple osteolytic lesions, of variable sizes, distributed predominantly in the axial skeleton but also affecting elements of the appendicular region. This individual also exhibits atypical manifestations of metastatic bone disease, in the form of acrometastases—metastases in the extremities, which are uncommon events in current clinical settings. The individual's skeletonized remains were exhumed from a crypt in the Chapel of the Holy Spirit ( Espírito Santo ), Loures, Portugal, and have been dated from the 16th to 19th centuries. The multiple osteolytic lesions, noted both by direct and radiological observations, are discussed to expand the knowledge regarding disease manifestations in the past but also to reflect on disability and suffering in past individuals affected by oncologic ailments.