Luc Buchet

Comparing discriminant analysis and neural network for the determination of sex using femur head measurements

The measurement of the femoral head is usually considered an interesting variable for the sex determination of skeletal remains. To date, there are few published reference measurements of the femoral head in a modern European population for the purpose of sex determination. In this study, 116 femurs from 58 individuals of the South of France (Nice Bone Collection, Nice, France) were studied. Three measurements of the femoral head were taken: the vertical head diameter (VHD), the transversal head diameter (THD) and the head circumference (HC). The results show that: (i) there is no statistical difference between the right and left femurs for each of the three measurements (VHD, THD and HC). Therefore we arbitrarily chose to use the measures from the right femurs (N=58) to pursue our experiments; (ii) the measurements of the femoral head are similar to those of contemporary American populations; (iii) the dimensions of the femoral head place the measurements of the French population somewhere between Germany or Croatia, and Spain; (iv) there is no significant secular trend (in contrast with the femoral neck diameter); (v) the femoral head measurement as a single variable is useful for sex determination: a 96.5% rate of accuracy was obtained using THD and HC measurements with the artificial neural network; and a 94.8% rate of accuracy using VHD, both with the discriminant analysis and the neural network.

Forensic aspect of cremations on wooden pyre

Three cases of cremation on open-air pyres are described. One was classified as a suicide and two as homicides. Fire duration was estimated at approximately 1 h, close to 2 h and more than 3 h, respectively. The position of the remains, the colour alteration of bone and the burned bone fractures biomechanics are discussed. Knowledge of normal burn patterns in fire and detection of perimortem lesions are essential. These three cases highlight the specific thermal alterations and burning processes in accordance with fire duration. In each case, careful investigation yielded clues as to the manner of death. Close cooperation between law enforcement and forensic pathology investigators is required in order to correctly identify the circumstances of death.

Model Life Tables for Pre-Industrial Populations: First Application in Palaeodemography

Contemporary model life tables cannot accurately reconstruct the mortality patterns experienced by pre-industrial populations. It has thus become essential to develop mortality models that are adapted to the populations studied by paleodemographers, and that fulfil a threefold objective: to be based on a sufficiently large set of tables representing early mortality at diverse times and places; to use entries that can be easily obtained from reliable and well-established anthropological indicators; and to take the population growth rate into account, despite the problem of calculating it from bone remains.

An amazing case of fatal self-immolation

We present a surprising case of suicide by self-immolation. A surveillance camera filmed the victims agony. We were able to ascertain that he survived 13 min after ignition. This case was the starting point for a review of the literature of the forensic elements required to correctly analyze cases of suicide by self-immolation and to establish the causal link between the burn lesions and death. The authors will focus on the forensic and medical aspects in favor of suicide by self-immolation and on the forensic aspects required to understand the ignition process, the circumstances surrounding the fire with a particular emphasis on determining whether an accelerant was doused on the victim before ignition.

Bone beveling caused by blunt trauma: a case report

The authors report a fatal case of blunt trauma to the skull caused by a rib of a beach umbrella. The skull displayed a round hole in the right temporal bone with typical internal beveling. Blunt trauma mimicking a gunshot wound (round perforation of the skull with internal beveling) is very rarely reported in the forensic literature.

Atouts d'une procédure récente d'inférence bayésienne pour l'étude de l'impact des crises démographiques. Application à trois sites médiévaux bas-normands

RésuméPour mettre en lumière les caractéristiques démographiques de populations issues de contextes archéologiques, le paléodémographe doit pouvoir restituer sans biais la composition par sexe et par âge de ces populations. Nous proposons pour cela une nouvelle procédure d’inférence bayésienne qui permet d’estimer des probabilités de décès, aux âges adultes, assorties de marges d’erreur fiables. Une telle analyse appelle quelques réflexions préalables. Tout d’abord, il convient de vérifier que les différences mises en évidence entre les sites ne peuvent pas être attribuées à des artefacts méthodologiques, notamment lors de l’observation de l’indicateur biologique. Elle suppose aussi l’acceptation du principe d’uniformité biologique entre les populations historiques et les populations de référence préindustrielles. Pour illustrer l’intérêt de cette démarche, nous l’avons appliquée à trois sites bas-normands d’époque mérovingienne susceptibles d’avoir été touchés par la crise démographique des premiers siècles du Moyen Âge décrite par les chroniqueurs et les historiens. Les résultats obtenus montrent clairement que le nombre de décédés est particulièrement élevé dans la première classe d’âge. Si l’explication peut être envisagée en termes de mortalité, on peut y voir aussi l’incidence de mouvements migratoires, cette hypothèse trouvant un écho dans les sources archéologiques qui voient le haut Moyen Âge comme une période d’immigration dans la plaine de Caen.AbstractTo bring out the demographic characteristics of populations from archaeological contexts, palaeodemographers have to determine their composition by sex and age without introducing any bias. The new Bayesian inference procedure proposed here for this purpose estimates the probabilities of death, for adult age groups, coupled with reliable margins of error. Some preliminaries have to be observed before undertaking this kind of analysis. First, it should be checked that differences identified between sites cannot be attributed to methodological artefacts, especially when observing the biological indicator. Second, the procedure rests on the assumption that the principle of uniformity among biological populations and historical preindustrial reference populations is accepted. To illustrate the usefulness of this approach, we applied it to three Merovingian sites in Lower Normandy that are likely to have been affected by the demographic crisis of the early Middle Ages described by chroniclers and historians. The results clearly show that the number of deaths is particularly high in the first age class, especially among males. While this could be explained in terms of mortality, the impact of migration could also be a factor, a hypothesis that is echoed in archaeological sources that consider the early Middle Ages to be a period of immigration into the Caen lowlands.

Age at Death: Current Approaches and Methods

To propose a palaeodemographic reconstitution from skeletal data, criteria accessible from historical and archaeological data must be used and, as a demographic study directly based upon archaeological data is not possible, tools must be defined to take account of osteological constraints. This chapter examines available tools and proposes some adaptations.

Current Demographic Models

The purpose of palaeodemographic analysis is to understand the population as it was, within a given socio-environmental context, where the individuals it comprised formed a dynamic group marked by births, deaths and sometimes migrations, and when all we have, at best, is the bones of those who died. This is no easy task and involves the use of population models and life tables or parametric models. The hypothesis required for such models are recalled and the main life tables actually used by demographers and palaeodemographers are reviewed.

Examples of Archaeological Applications

The demographic approach to buried populations can be now re-examined with the new “tools” proposed in this handbook. Some of the recurrent questions of palaeodemography, such as the problem of estimating the proportion of under-20s, as well as new research topics, can be explored from four case studies. For two of them, only biological data are available (burial grounds from Late Antiquity comprehensively excavated and covered by thorough historical, archaeological and anthropological studies). The last two are sites with extensive written documentation that provide information on the demographic behaviour of the exhumed populations.

Finding the Right Models for Pre-industrial Populations

As contemporary model tables, or mathematical models based on current conditions are not the best tools for describing pre-transitional human behaviour, characterized by very high rates of fertility and child mortality, specific models must be developed for preindustrial populations. These models must be based on a large corpus of tables that are statistically representative of mortality among pre-industrial populations, to propose inputs easily accessible from historical or osteological sources and to take account of the growth rate, either positive or negative, of the population.