Alexandra Boucherie

Dominique Castex

Caroline Polet

Sacha Kacki

Century

Normal growth, altered growth? Study of the relationship between Harris Lines and bone form within a post-medieval plague

Keywords:

come

Normal growth, altered growth? Study of the relationship between harris lines and bone form within a post-medieval plague cemetery (Dendermonde, Belgium, 16th Century)

Introduction

The occurrence of transverse highly mineralized lines on bones was noted for the first time by Wegner in 1874. Then, these features were intensively analyzed through clinical and experimental studies by H.A. Harris. They were subsequently named Harris lines (HLs).

Noticed in diabetic children and undernourished rats, HLs were promptly associated with episodes of arrested growth caused by unfavorable conditions during ontogenesis, i.e. infections, various diseases and nutritional deficiencies [START_REF] Harris | Lines of arrested growth in long bones in childhood: the correlation of histological and radiographic appearances in clinical and experimental conditions[END_REF].

Harris lines are commonly described as transverse lines of increased density visible on radiographs [START_REF] Harris | Lines of arrested growth in long bones in childhood: the correlation of histological and radiographic appearances in clinical and experimental conditions[END_REF][START_REF] Park | The imprinting nutritional disturbance on growing bones[END_REF]. Histologically speaking, HLs are oriented trabeculae that cross transversally the bone, and are especially present within the medullary cavity of the long bones [START_REF] Acheson | Effects of starvation, septicemia and chronic illness on the growth cartilage plate and metaphysis of the immature rat[END_REF][START_REF] Park | Transverse lines in bone: the mechanism of their development[END_REF]. They could be identified on various bones as vertebrae, ilium and patella [START_REF] Abraham | Growth arrest lines and recurrent patellar dislocation: a new sign[END_REF][START_REF] Cunningham | The appearance of Harris lines at the iliac crest[END_REF]Edwards, 1993;[START_REF] Sajko | Growth restart / recovery lines involving the vertebral body: a rare, incidental finding and diagnostic challenge in two patients[END_REF] even if they are mostly analyzed on long-bones and alleged to be most frequently found on distal end of tibiae [START_REF] Garn | Lines and bands of increased density : their implication to growth and development[END_REF][START_REF] Gindhart | The frequency of appearance of transverse lines in the tibia in relation to childhood illnesses[END_REF][START_REF] Park | Transverse lines in bone: the mechanism of their development[END_REF]. This higher frequency of HLs formed on the tibia is commonly explained through better blood circulation, an important concentration of osteoblasts and a greater sensitiveness to infections related to this bone [START_REF] Hughes | Transverse (Harris) lines in Irish archaeological remains[END_REF][START_REF] Ortner | Identification of Pathological Conditions in Human Skeletal Remains[END_REF][START_REF] Park | The imprinting nutritional disturbance on growing bones[END_REF].

The formation process of these transverse lines is widely well-known since the 1950s thanks to laboratory experimental studies on animals [START_REF] Acheson | Effects of starvation, septicemia and chronic illness on the growth cartilage plate and metaphysis of the immature rat[END_REF][START_REF] Mp | Experimental assessment of nutrition and bone growth's velocity effects on Harris lines formation[END_REF][START_REF] Park | Transverse lines in bone: the mechanism of their development[END_REF]. They represent a disturbance of the growth plate activity characterized by a reduced proliferation of chondrocytes, an extensive abnormal calcification and an unusual horizontally orientation in the deposition of osteoblasts. HLs can be formed during the growth process of an individual, in the metaphysis of the long bones, until the definitive growth plate closure. HLs are likely to be produced after stress episodes that generate a slowing down or an arrest of growth but some authors consider that for an effective HL formation the arrest of growth has to be complete and followed by a sufficient recovery [START_REF] Acheson | Effects of starvation, septicemia and chronic illness on the growth cartilage plate and metaphysis of the immature rat[END_REF][START_REF] Park | The imprinting nutritional disturbance on growing bones[END_REF][START_REF] Park | Transverse lines in bone: the mechanism of their development[END_REF].

Following the first works of H.A. Harris, several clinical studies were conducted on contemporary population to detect the etiology of HLs. Various factors were identified such as specific diseases like rickets, osteoporosis, malaria, children's illnesses and respiratory ones, e.g. pneumonia, measles, chickenpox, whooping cough [START_REF] Acheson | Effects of starvation, septicemia and chronic illness on the growth cartilage plate and metaphysis of the immature rat[END_REF][START_REF] Arnay-De-La-Rosa | Radiopaque transverse lines (Harris lines) in the Prehispanic population of El Hierro (Canary Islands)[END_REF][START_REF] Garn | Lines and bands of increased density : their implication to growth and development[END_REF][START_REF] Gindhart | The frequency of appearance of transverse lines in the tibia in relation to childhood illnesses[END_REF][START_REF] Harris | Lines of arrested growth in long bones in childhood: the correlation of histological and radiographic appearances in clinical and experimental conditions[END_REF][START_REF] Park | Transverse lines in bone: the mechanism of their development[END_REF]. Malnutrition and vitamin or protein deficiencies were also incriminated [START_REF] Acheson | Effects of starvation, septicemia and chronic illness on the growth cartilage plate and metaphysis of the immature rat[END_REF][START_REF] Blanco | Height, weight, and lines of arrested growth in young Guatemalan children[END_REF][START_REF] Dreizen | Influence of age and nutritional status on "bone scar" formation in the distal end of the growing radius[END_REF][START_REF] Harris | Lines of arrested growth in long bones in childhood: the correlation of histological and radiographic appearances in clinical and experimental conditions[END_REF][START_REF] Himes | Bone growth and development in protein-calorie malnutrition[END_REF]. Others authors found that HLs presence was linked to alcohol consumption [START_REF] Gonzalez-Reimers | Association of Harris lines and shorter stature with ethanol consumption during growth[END_REF]; immobilization and fractures [START_REF] Abraham | Growth arrest lines and recurrent patellar dislocation: a new sign[END_REF][START_REF] Sajko | Growth restart / recovery lines involving the vertebral body: a rare, incidental finding and diagnostic challenge in two patients[END_REF]Yao and Seeger, 1997); or psychological stress [START_REF] Khadilkar | Metaphyseal growth arrest lines in psychosocial short stature[END_REF]Teele, 1999). The association between HLs and systemic conditions such as illnesses and malnutrition was widely examined and recognized whereas local factors such as fracture were alleged to be less prone to cause HLs formation [START_REF] Garn | Lines and bands of increased density : their implication to growth and development[END_REF][START_REF] Hughes | Transverse (Harris) lines in Irish archaeological remains[END_REF][START_REF] Park | The imprinting nutritional disturbance on growing bones[END_REF].

The co-occurrence between HLs and deficient conditions led anthropologists to use HLs as an indicator to reconstruct health and nutritional status of past populations. These palaeopathological studies started to be conducted by North-American anthropologists [START_REF] Buikstra | The Caribou Eskimo: general and specific disease[END_REF][START_REF] Goodman | Harris lines as indicators of stress in prehistoric Illinois populations[END_REF][START_REF] Mchenry | Transverse lines in long bones of prehistoric California indians[END_REF] and were, in parallel, developed in Europe [START_REF] Hughes | Transverse (Harris) lines in Irish archaeological remains[END_REF][START_REF] Mays | The relationship between Harris lines and other aspects of skeletal development in adults and juveniles[END_REF][START_REF] Papageorgopoulou | Harris lines revisited : prevalence, comorbidities, and possible etiologies[END_REF][START_REF] Piontek | Harris lines in subadult and adult skeletons from the Mediaeval cemetery in Cedynia, Poland[END_REF][START_REF] Ribot | A study of non-specific stress indicators and skeletal growth in two mediaeval subadult populations[END_REF]. However, some authors have recently questioned this etiology and the status of HLs as an arrested growth indicator. Indeed, HLs could be visible on unhealthy children but also on healthy ones [START_REF] Dreizen | Influence of age and nutritional status on "bone scar" formation in the distal end of the growing radius[END_REF][START_REF] Gindhart | The frequency of appearance of transverse lines in the tibia in relation to childhood illnesses[END_REF]. Their co-occurrence with other stress indicators, i.e. linear enamel hypoplasia, was not proven conclusively as some authors found it [START_REF] Clarke | The association of early childhood enamel hypoplasias and radiopaque transverse lines in a culturally diverse prehistoric skeletal sample[END_REF] and others did not [START_REF] Alfonso | Reevaluating Harris Lines -A comparison between Harris lines and enamel hypoplasia[END_REF][START_REF] Mays | The relationship between Harris lines and other aspects of skeletal development in adults and juveniles[END_REF][START_REF] Mchenry | Transverse lines in long bones of prehistoric California indians[END_REF][START_REF] Ribot | A study of non-specific stress indicators and skeletal growth in two mediaeval subadult populations[END_REF]. Last but not least, HLs were rarely correlated to altered stature and shorter metrical parameters [START_REF] Mays | The relationship between Harris lines and other aspects of skeletal development in adults and juveniles[END_REF][START_REF] Papageorgopoulou | Harris lines revisited : prevalence, comorbidities, and possible etiologies[END_REF][START_REF] Piontek | Harris lines in subadult and adult skeletons from the Mediaeval cemetery in Cedynia, Poland[END_REF][START_REF] Ribot | A study of non-specific stress indicators and skeletal growth in two mediaeval subadult populations[END_REF]. Some authors have suggested that all these paradoxical points could be explained by a more physiological thesis [START_REF] Alfonso | Reevaluating Harris Lines -A comparison between Harris lines and enamel hypoplasia[END_REF][START_REF] Mp | Experimental assessment of nutrition and bone growth's velocity effects on Harris lines formation[END_REF][START_REF] Chaumoître | Analyse des stries d'arrêt de croissance sur deux populations du XVIIIème siècle provenant des charniers de peste de Marseille et Martigues[END_REF][START_REF] Gilde | Patterns of GH output and their synchrony with short-term height increments influence stature and growth performance in normal children[END_REF][START_REF] Papageorgopoulou | Harris lines revisited : prevalence, comorbidities, and possible etiologies[END_REF]. They have interpreted HLs as a result of normal saltatory growth process characterized by stasis and spurts. They have argued that HLs could be formed during accelerated growth, caused by hormonal secretions, without being associated with a stress episode.

In order to discuss the reliability of HLs as arrested growth indicator, we analyzed the relationship between HLs and metrical parameters within an archaeological sample composed of both subadults and adults. The aims were to test the potential incidence of HLs on length and shape of long bones and to interrogate their pattern of occurrence as concerns their age-atformation.

Material & Methods

The analysis was conducted on the skeletal material collected from the Maria Troon convent cemetery, situated in Dendermonde, Belgium. Historical sources indicated that the cemetery was created during a plague epidemic that raged in the city between 1579 and 1584. Among the epidemic victims, at least 120 individuals were alleged to be buried there. Plague is an infectious disease caused by the bacterium Yersinia pestis. It is formerly a disease of various rodent species, but it can be transmitted to human through animals' fleas. Throughout history, it causes at least three pandemics: Justinian plague (from 6 th to 8 th century), the Black Death (from 14 th century onwards), and the modern or Hong Kong plague (from 19 th to 20 th century).

In the post-medieval period, recurrent plague outbreaks occurred in Europe, including Belgium.

At Dendermonde, 99 individuals were excavated (table 1) and the hypothesis of a plague epidemic origin was strongly supported by the consistency between the dates given by the historical sources and the radiocarbon dating (end of the 16 th century and the early beginning of the 17 th century), by archaeological evidence, i.e. the recovery of several mass graves (simultaneous deposition) and by the highlighting of paleodemographical anomalies found to be similar to the ones identified in other plague cemeteries [START_REF] Margerison | Palaeodemographic comparison of a catastrophic and an attritional death assemblage[END_REF][START_REF] Castex | Identification and interpretation of historical cemeteries linked to epidemics[END_REF]Castex and Kacki, in press). In this context, a paleopathological analysis of this population became important to develop as the short time between burials indicates that these individuals lived at the same period under similar living conditions. Of the 99 skeletons recovered during the excavation, 69 were well preserved enough to search for HLs, including 28 adults and 41 subadults (table 2). The sex of adult individuals was determined using morphological characteristics of os coxae [START_REF] Bruzek | A method for visual determination of sex, using the human hip bone[END_REF][START_REF] Murail | DSP: a tool for probabilistic sex diagnosis using worldwide variability in hip-bone measurements[END_REF].

The age-at-death was estimated using several methods. For the subadults, we focused on the degree of mineralization of the teeth [START_REF] Moorrees | Age variation of formation stages for ten permanent teeth[END_REF]. When they were absent, the estimation was based on the length of long bones [START_REF] Maresh | Measurements from roentgenograms[END_REF] and the degree of epiphyseal fusion [START_REF] Coqueugniot | Brief Communication: Infracranial Maturation in the Skeletal Collection From Coimbra, Portugal: New Aging Standards for Epiphyseal Union[END_REF]. The adequacy between the age estimation based on dental mineralization and bone length was tested by applying a Wilcoxon T-test. No differences were highlighted (p>0.05), so that we decided to use both methods for age estimation.

Within the adult group, the younger adults (aged between 20 and 29 years old) were distinguished from the older ones (aged 30 years old and above) using the quotation of the latest ossification points [START_REF] Owings-Webb | Epiphyseal union of the anterior iliac crest and medial clavicle in a modern multiracial sample of American males and females[END_REF]. Antero-posterior radiographs were carried out on each preserved femur and tibia. These bones were selected since they were among the best preserved in the collection and known to be the most likely to present HLs [START_REF] Garn | Lines and bands of increased density : their implication to growth and development[END_REF][START_REF] Gindhart | The frequency of appearance of transverse lines in the tibia in relation to childhood illnesses[END_REF]. We selected bones free of pathology (e.g. fracture, infection), entire bones or bones with at least one extremity, i.e. distal one for the femur, proximal and/or distal end for the tibia (n=102 femoral ends, n=182 tibial ends). Radiographs were performed at the Royal Museum of Central Africa (Tervuren, Belgium) using a machine prototype (Visix) designed by two Belgian companies (Medex Loncin SA and Xris). The radiographs parameters applied were as following: 50-60 kV, 2000mA, 30 seconds exposure time and 1.6 m distance. Radiographs were saved as PNG files and the image processing was executed using Maestro © software.

The rating of HLs was performed by naked-eye by one of the authors (AB) following criteria defined by [START_REF] Goodman | Harris lines as indicators of stress in prehistoric Illinois populations[END_REF], registering a HL as any transverse line which extended at least one quarter across the bone width (figure 1). We registered the presence or absence of the indicator and specified the number of HLs observed at each extremity. Intra-observers errors were assessed by calculating a Cohen's Kappa coefficient [START_REF] Cohen | A coefficient of agreement for nominal scales[END_REF].

From this rating process, we developed an individual scale analysis by considering the maximal number of HLs observed at one extremity, femur or tibia, as the minimal number of stress episodes an individual had suffered during his life. Subsequently, we defined three groups:

group 0 was composed of individuals with no HL, group 1 grouped individuals whose bones have recorded one or two stress episodes, and group 2 represented the most stressed individuals, with more than two stress episodes recorded on bone. Comparisons of HLs prevalence between and within subadult and adult groups were performed using chi-square test. When sample sizes were small and expected cell frequencies less than five, we used Fisher's exact test instead.

Age-at-formation of each detected HL was calculated using Hummert and Van Gerven's method [START_REF] Hummert | Observations on the formation and persistence of radiopaque transverse lines[END_REF]. It allowed developing an analysis of the growth within the population, without comparing it to exterior modern growth data [START_REF] Hunt | The estimation of age at death and ages of formation of transverse lines from measurements of human long bones[END_REF][START_REF] Clarke | The association of early childhood enamel hypoplasias and radiopaque transverse lines in a culturally diverse prehistoric skeletal sample[END_REF][START_REF] Maat | Dating and rating of Harris's lines[END_REF][START_REF] Byers | Technical note: Calculation of age at formation of radiopaque transverse lines[END_REF]. This method is based on the restitution of the ossification center, considering that both extremities of long bone do not grow at the same rate e.g. 43% of growth of tibia occurs at the distal portion whereas it is 71% for the distal part of femur [START_REF] Anderson | Growth and predictions of growth in the lower extremities[END_REF]. To determine the age of each HL at the time of its deposition, the distance between the ossification center and the HL was measured, directly on radiographs, using Adobe Photoshop © software. Since we decided to work on age groups, we defined the growth pattern of the population for each group by considering the variation of lengths (minima and maxima) within the age range to reliably calculate the age-at-formation of HLs.

In order to investigate the relationship between HLs and growth, bone measurements were taken on both left and right elements (table 3). The cortical thickness of both femur and tibia were obtained from the radiographs, through calculation of the cortical index (CI) (Dequeker, 1976;[START_REF] Mays | The relationship between Harris lines and other aspects of skeletal development in adults and juveniles[END_REF]:

Bone Measurement Abbreviations

(from Brauer, 1988)

Femur Maximal length M1

Anterior-posterior subtrochanteric diameter M10

Medial-lateral subtrochanteric diameter M9

Anterior-posterior midshaft diameter M6

Medial-lateral midshaft diameter M7

Midshaft circumference M8

Epicondylar breadth M21

Tibia

Maximum length M1

Anterior-posterior diameter at nutrient foramen M8a

Medial-lateral diameter at the nutrient foramen M9a

Circumference at the nutrient foramen M10b

Maximal proximal epiphyseal breadth M3

Maximal distal epiphyseal breadth M6

HLs rating data were then coupled to these collected metrical parameters through a statistical analysis. The three defined groups were investigated to detect the influence of the presence and the number of HLs on metrical parameters. We tested the metrical differences between the individuals without HLs (group 0) and the individuals with HLs (groups 1 and 2); and between the individuals with few HLs (groups 0 and 1) and the individuals with many HLs (group 2).

We performed an ANOVA analysis and constructed boxplots for each metrical parameter. These statistical tests were separately carried out within the subadult and adult group. Within the adult group, the sex variable was taken into account.

All statistical analyses were performed in R © , version 3.0.2, with a p-value significance threshold of 0.05.

Results

The examination of 102 femoral extremities and 181 tibial ends revealed the presence of 159 HLs, which concerns 73 bony ends. HLs were present in 36 of 69 individuals (52%), including 24 subadults (59%) and 12 adults (43%). Although individuals younger than 20 years-old were more commonly affected than their older counterparts, the difference was not statistically significant (χ²=1.64, df=1, p=0.20). Within the subadult group, most of the individuals below 10 years showed at least one HL, whereas these features were statistically less common in older subadults (Fisher's exact test; p<0.01). Within the adult group, HLs prevalence was slightly higher in younger adults, but the difference with older adults was not significant (χ²=0.44, df=1, p=0.51). The overall prevalence and the prevalence for femur and tibia in each age group are presented in table 4. When we classified the individuals into groups (group 0, group 1 and group 2) according to the number of HLs they display, the distal end of tibia, if preserved, constantly showed the highest number of HLs, at least equally or more than the others extremities. For the 14 individuals that did not have preserved distal end of tibia, the classification was based on HL rating from another bone, from the proximal end of tibia for 5 cases, and from the distal femur for 9 cases. When these other ends were used, the individuals were classified into the group 0 (4 cases out of 33), the group 1 (6 cases out of 20) and into the group 2 (4 cases out of 16). This balanced division suggests that the use of another extremity did not entail a methodological bias and did not systematically put the individuals in the less stressed group. The Cohen's Kappa coefficients obtained by confronting two series of HLs rating from the observer are satisfactory in average (table 6). It confirmed the reproducibility of the observations and justified the robustness of the analysis performed on HLs prevalence. 7). The peak of HLs formation for subadults was between 5 and 9 years old. Within the adult group, the majority of HLs belonging to younger adults and older ones (50% to 58%) were formed between 10 and 14 years old. Only one out of 13 HL formed around one year old was belonging to an adult individual. Age-atformation was calculated for 13 HLs belonged to females and 26 HLs belonged to males (table 8). For females, the majority of lines were formed between 10 and 14 years old. For males, the same amount of HLs were formed between 5 and 9 years and between 10 and 14 years old individual with and without HLs was not balanced and the amount of collected measurements not sufficient. On the contrary, the whole adult sample was investigated by distinguishing younger and older adults.

Age group

Age

Subadult sample

The results of the ANOVA analysis revealed that the occurrence of HLs did not affect maximal femoral and tibial lengths for both sides (p-values>0.1, S-tables 1 and 2) within the subadult group.

However, significant differences were found when investigating shape parameters. Between the individuals without HLs and with HLs, five metrical parameters were impacted. Within the [5-9] age group, differences affected the antero-posterior sub-trochanteric diameter of the left femur, the distal breath of left femur and the proximal breadth of right tibia (p<0.05, S-table 1).

Within the [10-14] age group, values of the antero-posterior diameter at nutrient foramen of left tibia and circumference of right tibia were significantly different (p<0.05, S-table 1). Besides, differences in shape parameters between the individuals with few HLs and those with many HLs were also highlighted only within the [5-9] age group: three femoral shape parameters and three tibial shape parameters (p<0.05, S-table 2).

For all of these metrical parameters, boxplots demonstrated that subadults with the more HLs showed constantly slighter measurements than subadults with no or less HLs (figures 2 and 3).

Adult sample

When considering adult individuals, the results of the ANOVA analysis revealed that the occurrence of HLs did not affect maximal femoral and tibial lengths for both sides (p-values>0.1, S-tables 3 and 4). When the p-values were found to be significant, they were linked to shape measurements.

Within the younger adults, between the individuals without HLs and with HLs, eight parameters were significantly different, all related to shape parameter (p<0.05, S-table 3). Five femoral shape parameters and two tibial shape parameters were significantly distinct between the individuals with few HLs and with many HLs (p<0.05, S-table 4).

The constructed boxplots demonstrated that the males with HLs showed constantly larger measurements than the males without HLs. In contrast, females with HLs often displayed slighter measurements than females without HLs (figures 4 and 5).

Within the older adult group, no significant difference was found (S-tables 3 and 4).

Discussion

Prevalence An average prevalence of HLs was found in the post-medieval osteological collection of Dendermonde. Only half of the individuals showed at least one HL on the femur or tibia. The HLs prevalence at Dendermonde is part of the variability observed for this indicator in both plague and attritional cemeteries (table 9).

The prevalence of HLs between the subadult and the adult groups was not statistically different.

Similar results were found in both plague and attritional cemeteries [START_REF] Chaumoître | Analyse des stries d'arrêt de croissance sur deux populations du XVIIIème siècle provenant des charniers de peste de Marseille et Martigues[END_REF][START_REF] Mays | The relationship between Harris lines and other aspects of skeletal development in adults and juveniles[END_REF][START_REF] Nowak | Does the presence of Harris lines affect the final stature in a medieval population[END_REF][START_REF] Papageorgopoulou | Harris lines revisited : prevalence, comorbidities, and possible etiologies[END_REF]. Within the subadult sample, the younger ones showed statistically more HLs than the other ones. It may be either due to the fact that the younger subadults were more affected to stress episodes due to their inner frailty [START_REF] Saunders | Growth deficit in survivors and non-survivors: biological mortality bias in subadult skeletal samples[END_REF] or to the disappearance of some lines on older subadults due to active remodeling process [START_REF] Grolleau-Raoux | Harris Lines: a study of age-associated bias in counting and interpretation[END_REF]. Similarly, within the adult sample, more HLs were recorded on the younger individuals, although the statistical difference was not significant. The same trend was previously observed in two attritional cemeteries [START_REF] Gilde | Patterns of GH output and their synchrony with short-term height increments influence stature and growth performance in normal children[END_REF][START_REF] Beom | Harris lines observed in human skeletons of Joseon Dynasty, Korea[END_REF]. This decrease of HLs prevalence is consistent with a more prolonged remodeling process on older individuals due to their age-at-death.

Age-at-formation

At Dendermonde, the HLs age-at-formation distribution was different between the subadult and the adult group. Most of the subadults HLs were formed between 5 and 9 years old. This formation peak fits with observations made in previous archaeological studies where HLs were formed between 4 and 7 years [START_REF] Hummert | Observations on the formation and persistence of radiopaque transverse lines[END_REF][START_REF] Chaumoître | Analyse des stries d'arrêt de croissance sur deux populations du XVIIIème siècle provenant des charniers de peste de Marseille et Martigues[END_REF][START_REF] Papageorgopoulou | Harris lines revisited : prevalence, comorbidities, and possible etiologies[END_REF]. However, a formation peak around 2 and 3 year, not found here, was highlighted by clinical studies [START_REF] Dreizen | Influence of age and nutritional status on "bone scar" formation in the distal end of the growing radius[END_REF][START_REF] Gindhart | The frequency of appearance of transverse lines in the tibia in relation to childhood illnesses[END_REF]. On the contrary, most of the HLs observed on adults were formed between 10 and 14 years, as found in previous studies [START_REF] Ameen | Harris lines of the tibia across centuries: a comparison of two populations, medieval and contemporary in Central Europe[END_REF][START_REF] Nowak | Does the presence of Harris lines affect the final stature in a medieval population[END_REF][START_REF] Papageorgopoulou | Harris lines revisited : prevalence, comorbidities, and possible etiologies[END_REF]. Only one HL was formed before the end of an individual first year. This latter observation could be interpreted as a consequence of the remodeling process. Indeed, in adulthood, the oldest HLs are likely to be resorbed whereas HLs formed during the latest stresses are likely to be still visible [START_REF] Hughes | Transverse (Harris) lines in Irish archaeological remains[END_REF][START_REF] Hummert | Observations on the formation and persistence of radiopaque transverse lines[END_REF][START_REF] Lewis | Growing pains: the interpretation of stress indicator[END_REF]. However, it is noteworthy that none of the HLs recorded in the Dendermonde sample were formed between 15 and 19 years, i.e. the last period of bone growth. So, the remodeling process is not the only factor to explain the age-at-formation distribution. There is a significant span of HLs formation between 10 and 14 years.

HLs: a marker of arrested growth?

HLs have been associated to deficient health conditions since the initial work of H.A. [START_REF] Harris | Lines of arrested growth in long bones in childhood: the correlation of histological and radiographic appearances in clinical and experimental conditions[END_REF] They are commonly considered to be subsequent to pathological factors (illnesses, infections, nutritional deficiencies) which abnormally slow and arrest bone growth. In the present study, a systematic confrontation of HLs rating data and metrical parameters of the individuals was performed in order to discuss the reliability of this pathological thesis. We took as a widely accepted assumption that if HLs were the result of arrested growth, the most HLs an individual had the most altered would be his growth and the shortest would be his metrical parameters. HLs would be associated with a negative impact on the growth pattern. The defined groups of individuals were confronted to test both influence of the presence and the number of HLs on the bone measurements. The main asset of the narrow chronology of the Dendermonde collection was to provide a snapshot of a population living at the same period under similar living conditions. Therefore, the results obtained from ANOVA analysis on metrical parameters were not influenced by secular variations, unlike previous studies (e.g. [START_REF] Mays | The relationship between Harris lines and other aspects of skeletal development in adults and juveniles[END_REF]Nowak and[START_REF] Nowak | Does the occurrence of Harris lines affect the morphology of human long bones?[END_REF][START_REF] Mp | Experimental assessment of nutrition and bone growth's velocity effects on Harris lines formation[END_REF][START_REF] Papageorgopoulou | Harris lines revisited : prevalence, comorbidities, and possible etiologies[END_REF][START_REF] Ribot | A study of non-specific stress indicators and skeletal growth in two mediaeval subadult populations[END_REF].

Within the subadult group, we demonstrated that the presence of HLs had no significant impact on the size of individuals. The absence of correlation between HLs and stature matches previous archeological studies [START_REF] Mays | The relationship between Harris lines and other aspects of skeletal development in adults and juveniles[END_REF][START_REF] Papageorgopoulou | Harris lines revisited : prevalence, comorbidities, and possible etiologies[END_REF]. Even combined with other stress indicators (linear enamel hypoplasia, cribra orbitalia, periostitis) [START_REF] Ribot | A study of non-specific stress indicators and skeletal growth in two mediaeval subadult populations[END_REF] did not find significant differences between individuals with and without HLs, as regards maximal length of humerus, femur and tibia.

However, our results show that several shape parameters were negatively affected by the presence of HLs. Subadults with HLs displayed constantly slighter shape measurements than individuals without HLs. These findings are consistent with Mays' observations at Wharram Percy on femoral cortical index [START_REF] Mays | The relationship between Harris lines and other aspects of skeletal development in adults and juveniles[END_REF]. The investigation on other shape parameters has not been done prior to this study.

The difference of impact between size and shape parameters can be explained by the fact that catch-up following growth arrest occurs preferentially for bone length rather than bone width [START_REF] Garn | Lines and bands of increased density : their implication to growth and development[END_REF][START_REF] Himes | Bone growth and development in protein-calorie malnutrition[END_REF][START_REF] Mays | The relationship between Harris lines and other aspects of skeletal development in adults and juveniles[END_REF]. Additionally, the correlation between HLs presence and shorter measurements for some shape parameters seems to indicate that the growth of the individual has been disturbed by a temporary arrest. Pathological and unfavorable socioeconomic conditions are likely to be at the origin of this arrest and to be the underlying causes of the formation of most of the HLs in the subadult sample. But, we cannot exclude that these HLs could have formed after a normal physiological stasis preceding a spurt. Though, it remains complex to understand why this following spurt had not entailing a normal growth catch-up on the shape measurements.

Cautiousness is needed when looking at these results as several factors could limit the interpretation. Firstly, we had no access to the biological sex of the subadults as any existing methods was not reliable enough [START_REF] Lewis | The bioarchaeology of children. Perspectives from biological and forensic anthropology[END_REF][START_REF] Sutter | Nonmetric subadult skeletal sexing traits. I. A blind test of the accuracy of eight previously proposed methods using prehistoric known-sex mummies from Nothern Chile[END_REF]. By a sample bias, any subadult with HLs could have been a girl with commonly slighter metrical parameter (Tanner, 1960).

Also, the age range of subadult groups was wide. Thereby, the subadults with HLs could have displayed shorter shape parameters because they were the youngest in the age range. The size of the subadult sample is above all limiting further interpretations.

Regarding the adult group, significant differences were obtained only for the younger adults.

The absence of differences for the older adults could be the consequence of the remodeling process which obscures the relationship between HLs and metrical parameters [START_REF] Lewis | Growing pains: the interpretation of stress indicator[END_REF][START_REF] Mays | The relationship between Harris lines and other aspects of skeletal development in adults and juveniles[END_REF]. As observed in previous anthropological studies, no difference between individuals with and without HLs was found when investigating size parameters [START_REF] Mays | The relationship between Harris lines and other aspects of skeletal development in adults and juveniles[END_REF][START_REF] Papageorgopoulou | Harris lines revisited : prevalence, comorbidities, and possible etiologies[END_REF][START_REF] Nowak | Does the presence of Harris lines affect the final stature in a medieval population[END_REF]. The absence of impact of HLs on cortical index matches with Mays' study [START_REF] Mays | The relationship between Harris lines and other aspects of skeletal development in adults and juveniles[END_REF]. At Dendermonde, the presence of HLs did affect only shape parameters, as femoral diameter, circumference and distal breath; and tibial diameter and circumference. Only one previous archaeological study deals with such measurements. [START_REF] Nowak | Does the occurrence of Harris lines affect the morphology of human long bones?[END_REF] investigated the influence of HLs on bone form on the adult individuals of the Cedynia medieval cemetery (Poland). They found significant differences between individuals by the presence of the indicator for shape measurements on humerus, radius and tibia.

The impact of HLs on adult shape parameters was noted to be different by the sex. Males with HLs showed constantly larger shape parameters than individuals without HLs. A similar trend is observed within the Cedynia collection [START_REF] Nowak | Does the occurrence of Harris lines affect the morphology of human long bones?[END_REF]. However, for females the pattern was less clear, perhaps due to minor fluctuations.

In both subadult and adult samples, there are differences in some shape parameters between individuals with HLs and individuals without. The shape parameters concerned are similar for femur and tibia, i.e. antero-posterior diameters and shaft circumference. It appears that HLs have a significant impact on shape parameters regardless of the bone. The nature of the impact is, however, distinct between the two samples: negative in the subadult sample and positive in the adult one. The positive impact of HLs presence, especially on males shape parameters, seems obviously inconsistent to the main assumption considering HLs as a marker of arrested growth.

New insights to identify HLs etiology

Results obtained from ANOVA tests were contradictory, at Dendermonde, between the subadult and adult groups. Additionally, it is noteworthy that HLs observed in subadults and adults did not form at the same age: most of the HLs recorded in subadults were formed between 5 and 9 years whereas most of the HLs observed in their older counterparts were formed between 10 and 14 years.

The period between 5 and 9 years, corresponding to childhood, is recognized as a period of relatively stable and softened growth and sexual dimorphism [START_REF] Rogol | Growth at puberty[END_REF][START_REF] Dattani | Growth hormone deficiency and related disorders: insights into causation, diagnosis and treatment[END_REF]. Growth stasis and spurts of physiological origin are reduced at these ages.

Therefore, most of the HLs formed at this period, are likely to be linked to unfavorable conditions, pathological or socio-economic, which can occasion growth failures.

In contrast, the peak of HLs formation between 10 and 14 years fits with the puberty stage characterized by an increased growth velocity, under growth hormones and sexual steroids influence [START_REF] Dattani | Growth hormone deficiency and related disorders: insights into causation, diagnosis and treatment[END_REF]. HLs formed between 10 and 14 years are likely to be the result of a normal saltatory growth [START_REF] Lampl | Identifying saltatory growth patterns in infancy: a comparison of results based on measurement protocol[END_REF] and to represent the hallmark of puberty: the adolescent growth spurt. It could explain why the males with HLs displayed larger parameters than males without HLs, at Dendermonde. The fact that the females did not follow the same pattern tends to indicate that their pubertal tempo growth is less irregular and intensive than the males' one [START_REF] Gilde | Patterns of GH output and their synchrony with short-term height increments influence stature and growth performance in normal children[END_REF][START_REF] Rogol | Growth at puberty[END_REF][START_REF] Marceau | Individual differences in boys' and girls' timing and tempo of puberty: modeling development with nonlinear growth models[END_REF].

But, growth is a less simple process in detail, and discordance exists between short-term and long-term growth patterns. While long-term growth seems linear, especially during the midchildhood, from a short-term point of view this period can be rhythmed by diurnal and seasonal growth variations, alternating stasis and spurts [START_REF] Butler | The cyclical nature of prepubertal growth[END_REF][START_REF] Gelander | Seasonality in lower leg length velocity in prepubertal children[END_REF]Thalange et al., 1996). Growth velocity is also known to reach a nadir, called preadolescent dip, when approaching the puberty [START_REF] Rogol | Growth at puberty[END_REF]. Due to this complexity, we cannot exclude the possibility that some HLs formed between 5 and 9 years represent physiological spurts or stasis, even though it seems unlikely that such short-term fluctuations can alter metrical parameters on long-term, as they did on Dendermonde subadult individuals.

If we compare age-at-formation distribution at Dendermonde with larger archaeological studies, it appears that similar results have been previously found (table 10). HLs observed on subadult individuals are frequently formed around two age peaks, 0-2 years and 5-11 years.

They are interpreted as a result of various causes: weaning period for the earliest ones, childhood stresses linked to poor health and living conditions or vulnerability associated with prepubertal growth spurts for the latest ones. At Dendermonde, the latter factors are likely to cause the HLs formed between 5 and 9 years, in subadults. Regarding adult individuals, HLs are often formed during the pubertal period, i.e. 10-16 years, and formed earlier on females.

They are constantly interpreted as reflecting the adolescent growth spurt. HLs visible on Dendermonde adult individuals are therefore likely to represent physiological events. However, it needs to be bore in mind that such comparisons between archaeological sites are in some extent skewed because of existing interpopulation variations. Interpretations given here, regarding HLs origins and their impact on growth, need to be taken cautiously since they are deduced from modern growth patterns. The exact growth pattern at Dendermonde, in the late 16th century, is unknown, and it may have displayed distinct characteristics from the actual standards. For instance, it is possible that growth velocity was slower or more irregular than today and that growth spurts occurred earlier than the ones defined nowadays. Such discrepancies are plausible, but they cannot be detected by confronting dental ages with bone dimensions due to the small size of the Maria Troon skeletal sample. The implication of socioeconomical factors on growth is also a great limitation to the application of modern standards on archaeological sample (WHO Multicenter Growth Reference Study Group, 2006;[START_REF] Butte | Evaluation of the feasibility of international growth standards for school-age children and adolescents[END_REF].

Despite these limitations, the results of the analysis suggest that HLs formed at different age periods may not reveal the same underlying factors. The early formed HLs could be linked to diverse causes, and mostly reflecting pathological conditions whereas the HLs formed around the puberty are more likely to be physiological and hormonal lines [START_REF] Alfonso | Reevaluating Harris Lines -A comparison between Harris lines and enamel hypoplasia[END_REF][START_REF] Mp | Experimental assessment of nutrition and bone growth's velocity effects on Harris lines formation[END_REF][START_REF] Papageorgopoulou | Harris lines revisited : prevalence, comorbidities, and possible etiologies[END_REF][START_REF] Gilde | Patterns of GH output and their synchrony with short-term height increments influence stature and growth performance in normal children[END_REF]. Such interpretations need to be confirmed in the future by further analyses aiming to reconstructing growth patterns on larger osteological samples.

Conclusion

This study contributes to the question of the HLs etiology by providing new insights on the influence of HLs on bone parameters of archeological individuals. Its results suggest that the causes of HLs could be diverse, pathological or physiological, depending on the period of life during which they were formed. HLs should not systematically be considered as synonym of pathological arrest of growth, especially for those formed during puberty when the growth process is characterized by the adolescent spurt.

From now on and in future anthropological studies, the etiology of HLs should be interpreted depending on their age-at-formation. It would be important to distinguish the lines formed during a period characterized by stable growth from those formed during accelerated growth period (physiological lines). In the perspective of a paleopathological study on past population, it would be necessary to focus only on the former ones since lines of physiological origin are unlikely to represent the health impairments of a population.

Perhaps, a re-evaluation of the concept of stress is also needed [START_REF] Reitsema | Reconciling "stress" and "health" in physical anthropology: What can bioarchaeologists learn from the other subdisciplines?[END_REF]Temple and Goodman, 2014)

Figure 1 .

 1 Figure 1. Example of Harris lines, indicated by arrows, on the distal end of a right tibia (Dendermonde, skeleton 14, 5-9 year old), Scale: 1 cm.

Figure 2 .

 2 Figure 2. Box-plot showing metrical differences between the three groups of individuals by HLs presence, anterior-posterior subtrochanteric diameter (left femur, [5-9] age group).

Figure 3 .

 3 Figure 3. Box-plot showing metrical differences between the three groups of individuals by HLs presence, anterior-posterior diameter at midshaft (left femur, [5-9] age group).

Figure 4 .

 4 Figure 4. Box-plot showing metrical differences between the younger adults without HLs and with HLs by sex group, femoral distal breadth (left femur, younger adults).

Figure 5 .

 5 Figure 5. Box-plot showing metrical differences between the younger adults without HLs and with HLs by sex group, anteroposterior midshaft femoral diameter (left femur, younger adults).

Table 1 . Age and sex distribution of individuals from Dendermonde collection. Age-group Sex Total

 1

		Females Males Indeterminable
	1-4 years	0	0	5	5
	5-9 years	0	0	11	11
	5-9 / 10-14 years	0	0	12	12
	10-14 years	0	0	17	17
	10-14 / 15-19 years	0	0	5	5
	15-19 years	2	0	6	8
	20-29 years	8	8	3	19
	30+ years	9	10	3	22
	Total	19	18	62	99

Table 2 .

 2 Age and sex distribution of radiographed individuals from Dendermonde collection.

	Age-group		Sex		Total
		Females Males Indeterminable
	1-4 years	0	0	4	4
	5-9 years	0	0	8	8
	5-9 / 10-14 years	0	0	7	7
	10-14 years	0	0	15	15
	15-19 years	2	0	5	7
	Younger Adults	7	5	0	12
	Older Adults	8	8	0	16
	Total	17	13	39	69

Table 3 .

 3 List of bone measurements taken on femora and tibiae of Dendermonde collection, fromBrauer, 1988.

Table 4 .

 4 Prevalence of HLs per age groups and per bones (femora and tibiae) within Dendermonde collection.

				Age groups
		1-4	5-9	5-9 / 10-	10-14	15-19	Younger	Older
		years	years	14 years	years	years	Adults	Adults
	n	4	8	7	15	7	12	16
	Individuals
	with HLs (both bones	100%	88%	57%	40%	43%	50%	38%
	considered)
	Femora with HLs	100%	63%	0%	0%	0%	16%	6%
	Tibiae with HLs	75%	88%	57%	40%	43%	34%	32%

Table 5 .

 5 Classification of individuals into 3 groups according to the number of HLs rated, Group 0: no HL, Group 1: HLs indicative of one or two stress episodes, Group 2: HLs indicative of more than 2 stress episodes, within Dendermonde collection.

		Group 0 Group 1 Group 2
	Subadults	17	14	10
	Adults	16	6	6
	Total	33	20	16

Table 6

 6 Age-at-formation could only be assessed for entire bones. On the 159 recorded HLs, we could calculate this age for 145, i.e 91% of observed HLs (table

		Distal femur	Proximal tibia	Distal tibia
		Presence	Number	Presence	Number	Presence	Number
	Right	0.767	0.798	0.948	0.687	0.491	0.888
	Left	0.657	0.618	0.827	0.664	0.657	0.647

. Intra observer errors (Cohen's Kappa coefficient) calculated for Harris Lines rating (presence and number) by anatomical region for two series of observations, in italic: satisfactory agreement (0.61-0.80), in bold: excellent agreement (0.81-1.00), from

Landis and Loch (1977)

.

Table 7 .

 7 Distribution of age-at-formation of HLs by age group within Dendermonde collection.

Table 8 .

 8 Distribution of age-at-formation of HLs by age group for sexed individuals, within Dendermonde collection.

Comparison of bones size and shape between individuals with and without HLs could only be performed for two subadult age groups: [5-9] and [10-14] age groups. We excluded individuals upon these two age groups because it would not have been relevant to compare metrical parameters of individuals whose age could differ more than 5 years. It was also not possible to carry out statistical tests on the [1-4] and

[15][16][17][18][19]

age groups as the headcount between

Table 9 .

 9 HLs prevalence for all age groups observed in plague and attritional cemeteries from medieval and modern periods.

						Sample
		Site	Location	Dates	Identification -HLs criteria	Size (all age	HLs prevalence	References
						groups)
		Maria Troon Dendermonde	Dendermonde Belgium	1579-1584 AD	≥ 25% diaphysis width	69	52%	Present study
	Plague	Les Fédons	Lambesc France	1590 AD	≥ 30% diaphysis width	38	29%	Fiscella, 2007
	Cemeteries	Vodroffsgaard	Copenhagen Denmark	1711-1712 AD	≥ 30% diaphysis width	24	12%	Fiscella et al., 2008
		Observance and Delos	Marseille France	1720-1722 AD	≥ 25% diaphysis width	113	64%	Chaumoître, 2007
		Kulubnarti	Soudan Nubia	6-15 th century	≥ 50% diaphysis width	324	76%	Hummert and Van Gerven, 1985
		Unterseen and Oberbueren	Bern Canton Switzerland	7-15 th century	≥ 25% diaphysis width	112	78%	Ameen et al., 2005
		Cedynia	Poland	10-14 th century	≥ 25% diaphysis width	324	74%	Piontek et al., 2001
	Attritional cemeteries	Tomils	Bern Canton Switzerland	11-15 th century	≥ 30% diaphysis width	241	77%	Papageorgopoulou et al., 2011
		Waterford and Tintern	Irland	11-17 th century	≥ 25% diaphysis width	73	36%	Hughes et al., 1996
		Saint-Maurice	Val de Marne France	17 th century	≥ 25% diaphysis width	65	20%	Hadjouis and Amar, 2009
		Wharram Percy	Yorkshire UK	10-19 th century	≥ 50% diaphysis width	288	28%	Mays, 1995

Table 10 .

 10 HLs age-at-formation distribution observed in cemeteries from medieval and modern periods.

	Site	Dates	Sample size	HLs prevalence	HLs age-at-formation Subadults Adults	Interpretations Subadults Adults	References
	Maria Troon
	Dendermonde
	(Belgium)

  . Anthropologists include under this umbrella term any disruptive Tanner JM. 1960. Human growth. London:Pergamon press. 120 p. Temple DH, Goodman AH. 2014. Bioarcheology has a "health" problem: conceptualizing "stress" and "health" in bioarcheological research. Am J Phys Anthropol 155:186-191. Teele RL. 1999. Femoral growth lines: bony birthmarks in infants. Am J Roent 173:719-722. Thalange NKS, Foster PJ, Gill MS, Price DA, Clayton PE. 1996. Model of normal prepubertal growth. Arch Dis Child 75:427-431. WHO Multicentre Growth Reference Study Group. 2006. WHO Child Growth Standards based on length/height, weight and age. Acta Paediatr 450:76-85.

Acknowledgements:

The results of this research had been obtained from a master's thesis (A.B.) developed at the University of Bordeaux, within the PACEA laboratory (UMR 5199).

The authors thank the Royal Belgian Institute of Natural Sciences (Brussels) for providing the skeletal material and the Royal Museum for Central Africa (Tervuren) for acquiring the radiographs. Gratefulness goes to the Maison des Sciences de l'Homme d'Aquitaine (Pessac) for funding this research. Thanks also go to the PACEA laboratory researchers for their help regarding radiographs treatment and statistical analyses; to C.R. Dyche and K. Bowgen for proofreading the article; and to the reviewers for their comments which contribute to the improvement of the paper.

event which leads to impairments, as arrest of bone or teeth growth. It is considered as the shadow face of adaptation [START_REF] Goodman | Biocultural perspectives on stress in prehistoric, historical, and contemporary population research[END_REF]. However, the present study suggests that HLs following pubertal stage have a positive response on the growth dynamic. Thus, a stress indicator is not systematically synonym of negative impact on the organism.

To elucidate the etiology of HLs, the results obtained here need to be confirmed by further analyses, by applying similar methodological approach on larger osteological samples.

Comparing HLs formed at different age with other stress indicators would be promising to precise the relationship between the lines and the health status.

Author contributions: This research was designed by DC, SK and CP for a master thesis developed at the University of Bordeaux. The data collection was executed at the Royal Belgian Institute of Natural Sciences (Brussels) by AB, with the assistance of SK and CP, and the data treatment was executed by AB at the University of Bordeaux. AB and SK both worked on the final version of the paper.


Plague in diachronic and interdisciplinary perspective. Report on Session TH5-05 at the 22nd Annual Meeting of the EAA in Vilnius, Lithuania Doris Gutsmiedl-Schümann, Sacha Kacki, Marcel Keller and Christina Lee Plague, an infectious disease caused by the bacterium Yersinia pestis, occurred in at least three major historical pandemics: the Justinianic Plague (6th to 8th century), the Black Death (1348-1352, with further epidemic outbreaks until the 18 th century), and the Modern or Hong Kong Plague (19th to 20th century). However, it appears that the disease may be much older: DNA from Bronze Age human skeleton has recently shown that plague first emerged at least as early as 3000 BC. As any disease, plague has both a biological as well as a social dimension. Different disciplines can therefore explicate different aspects of plague which can lead to a better understanding of the disease and its medical and social implications.

The session was held on 2nd September 2016 as part of the 22nd Annual Meeting of the EAA with the aim of bringing together researchers from different disciplines who work on plague. It addressed a series of research questions, such as:

 Which disciplines can contribute to the research on plague?  What are their methodological possibilities and the limitations of their methodologies?  How can different disciplines work together in order to gain a more realistic and detailed picture of plague in different periods and regions?  How did different societies react to plague? In which way may we prove or disprove evidence for such reactionsand which disciplines may contribute to the debate?  What where the common aspects, and what the differences of the various plague outbreaks? Are there any epidemiological characteristics that are essential and/or unique to plague?  What are possible implications of the pandemic spread and endemic occurrence of plague through the ages for the interpretation of historical and cultural phenomena?

The session ran over a full day, with 13 papers and one poster from contributors originating from six different countries: Canada, Denmark, Germany, Great Britain, Norway and USA. It opened with an introduction by Marcel Keller (Max Planck Institute for the Science of Human History, Germany), who gave a short review of the history of plague research from the 1890s (when Alexandre Yersin in 1984 discovered the bacterium Y. pestis as causative agent of plague in Hong Kong, and Paul-Louis Simond evidenced in 1898 the role of rats and rat fleas in the transmission of the disease) until recent times. He pointed out some milestones and main controversies in the history of plague research in different disciplines like history, archaeology, palaeogenetics, and epidemiology. In a second talk, Wyndham Lathem discussed his recent results of microbiological studies reconstructing the evolutionary history of pathogenic Yersiniae and Y. pestis in particular. He could show that the 'ancestral' Y. pestis was able to cause primary pneumonic plague and to spread directly via droplet infection, and not until later gained the ability to cause bubonic plague and adapted for the specific transmission route and insect vector.

Eva Panagiotakopulu (University of Edinburgh, Great Britain) detected plague and rat evidence in written texts in Mesopotamia and Egypt. She suggested that the bacterium Y. pestis and the black rat might both have spread from Central Asia along trading routes for lapis lazuli to Egypt. She showed that the regular flooding of the Nile brought humans and rats together in the remaining relatively small areas which were not affected by flooding, where Y. pestis could be easily be transferred from rats to humans.

Simon Rasmussen (Technical University of Denmark) presented the results from an investigation of 100 Bronze Age skeletal samples that lead to the detection of the so far oldest genetic evidence for Y. pestis. He connected a mass migration from the Steppes at the beginning of the Bronze Age and the contemporary population decline in Central Europe with local outbreaks of plague during this period.

Lars Walløe (University of Oslo, Norway) linked the Philistine epidemic, which is reported in the Bible (1. Sam. 6,5), to plague. Going back to the original Hebrew sources and later translations, he showed that an ignorance of specific diseases may lead to misinterpretation and inaccurate translations. This paper also suggested that the enigmatic sudden decline of the Mycenaean culture around BC 1200, which is mentioned in the Hebrew Chronicles, may be explained through an outbreak of this devastating disease.

John Mulhall (Harvard University, USA) revisited ancient written sources, where a close philological study uncovered evidence for plague in the medical sources of Antiquity, in particular the Hippocratic Corpus, Rufus of Ephesus, and Galen. The picture that emerges from the medical sources is that Y. pestis is not mentioned in the Hippocratic Corpus and was unknown to medical writers until around the first century BC, when sources cited by Rufus of Ephesus report a disease which resembles plague. It remains familiar to medical authors from the first century BC to the end of the first century AD, when both Rufus and Aretaeus demonstrate an awareness of Y. pestis. Intriguingly, Galen, who wrote only a few generations after Rufus in the mid-second century AD, does not show any awareness of bubonic plague.

Jennifer Klunk (McMaster University, Canada) introduced the phylogenetic tree of the plaguecausing pathogen Y. pestis. Her presentation illustrated how genomic research of the last years has expanded this phylogenetic tree and led to the conclusion that the first and the second pandemic emerged independently from rodent reservoirs to humans.

Early medieval examples of plague graves from the cemeteries of Aschheim-Bajuwarenring and Altenerding/Klettham, both from Upper Bavaria, Germany, were investigated by Doris Gutsmiedl-Schümann (Freie Universität Berlin, Germany). Both cemeteries show that plague victims were prepared for burial, and dressed and buried just like other deceased of their time.

The grave construction, grave goods and layout did not differ from anyone who had not succumbed to the Justinianic Plague.

Michal Feldman (Max Planck Institute for the Science of Human History, Germany) presented recent results of a high coverage Y. pestis genome obtained from the previously presented site of Altenerding/Klettham. She showed that the same strain of Y. pestis was present in both Altenerding and Aschheim, and that this strain associated with the Justinianic Plague is likely to have become extinct.

Henry Gruber (Harvard University, USA) re-visited written sources. He showed that although there are no known texts from early medieval Valencia (Spain) which specifically mention the Justinianic Plague, there are written sources that might indicate the presence of the disease during the Visigothic period. He argued that burial regulations adopted by the Council of Valencia, held in 546 AD, could be linked to plague epidemics. He also argued for a closer investigation of written sources, not only for direct mentions or descriptions of the Justinianic

  After this short introduction, Wyndham Lathem (Northwestern University, USA) introduced the three species of the Yersinia bacteria that cause disease in humans: Y. enterocolitica, Y. pseudotuberculosis, and Y. pestis. While Y. enterocolitica and Y. pseudotuberculosis cause mild, self-limiting gastrointestinal infections, Y. pestis is responsible for the rapidly progressing, invasive, and often fatal disease called plague. Although Y. pestis is thought to have killed over 200 million people throughout history, it is a relatively "young" pathogen, only recently emerged from Y. pseudotuberculosis between 5,000 -20,000 years ago.

Plague, but for new regulations and changes which may have been implemented because of the disease, but which do not explicitly refer to it.

Aside from humans, domestic animals, too, could be affected by plague, as shown by Ptolemaios-Dimitrios Paxinos (Ludwig-Maximilians-Universität München, Germany). By using a zooarchaeological approach he demonstrated that a reduction of the size of a livestock occurred at various sites in the aftermath of the Black Death. He interprets this data as the result of deterioration in the living condition of such animals, either because of a climatic shift that leads to a shortage of fodder, or due to poor management by humans.

Julia Gamble (University of Toronto, Canada) investigates the mid-14th century Black Death by studying several burial sites from Denmark. She reported on the preliminary results of the study from an international team combining bioarchaeological and molecular methods that aims to further understand the epidemiology of plague in this region of Europe. her presentation, she described three cemeteries containing plague victims which were confirmed through the recovery of Y. pestis DNA from the skeletal material. She compared this information with archaeological and anthropological evidence from these sites.

The final paper, presented by Maria A. Spyrou (Max Planck Institute for the Science of Human History, Germany) looked at reconstructed Y. pestis genomes from plague victims of the Black Death and in comparison with subsequent plague outbreaks. The DNA was obtained from three archaeological sites in Spain, Germany and Russia. The results of her study provides support for the hypothesis of a single entry of Y. pestis in Europe during the Black Death, with a later spread towards Asia, where it remained and became the source for the third pandemic, and contemporary outbreaks of the disease worldwide.

Before opening the final discussion there was a poster presentation by Katherine Eaton (McMaster University, Canada). She hypothesizes that historical outbreaks of plague may be reconstructed by mapping historic documents, which can offer a new framework for future palaeogenetic studies.

The sessions were interspersed with opportunities for discussion, in which speakers and the audience had more time to engage in a fuller debate of the research presented in the papers. The discussions and chat continued informally after the end of the session in a cozy cafe in the old town of Vilnius.