Material Report
Early stress variation reflected in adult vertebral neural canal size within a medieval silver-mining population from Kutná Hora (Czech Republic)
2024 Volume 132 Issue 2 Pages 151-162
Details
2024 Volume 132 Issue 2 Pages 151-162
Previous bioarchaeological and auxological research has indicated that stunting the growth of vertebral measures, specifically those of the vertebral neural canal (VNC), provides a record of stressful early-childhood episodes that persists into adulthood. The main goal of this study was to investigate possible VNC size variation within the specific context of a medieval silver-mining site. Skeletons unearthed recently at Kutná Hora–Sedlec (Czech Republic) represent a population that lived there during its most prosperous era (13th–16th centuries). During this period, Kutná Hora residents could have faced both environmental and cultural conditioned stressors. In a total of 207 individuals examined in this study, we measured anteroposterior (AP) and transverse (TR) vertebral neural canal dimensions together with anterior vertebral body height (BH) in thoracic (Th10–Th12) and lumbar (L1–5) vertebrae, and analysed them for association with sex, age-at-death, and burial context (individual vs mass graves). These intra-site comparisons revealed that: (1) male diameters were consistently larger than female; (2) males with stunted AP and TR diameters were less likely to survive into mature adulthood; (3) the relationship between early life stress and burial context was very weak (in females) or non-existent (in males); and (4) the TR dimension of the vertebral neural canal was more prone to growth disruption than the AP or BH diameters.
An important part of the existing corpus of bioarchaeological knowledge comprises studies dealing with poor health and non-specific stress in early life (Klaus, 2014; Lorentz et al., 2019; Ham et al., 2021). Due to high growth rates, early infancy and childhood are particularly sensitive to environmental stressors such as nutritional deprivation, infection, poor socioeconomic status, and psychosocial adversity (Eveleth and Tanner, 1991; Skuse et al., 1994; Bogin, 1999). Bouts of stress experienced during childhood and/or adolescence can leave temporary or permanent marks on bone and teeth (Goodman and Armelagos, 1989) and can be explored using traditional markers of stress such as porotic changes, periostitis (Pilloud and Schwitalla, 2020), Harris lines (Boucherie et al., 2017), permanent tooth enamel defects, and stunted stature or long bone lengths (Hawks et al., 2022). Less frequently, developmental instability under systemic stress is inferred from asymmetry in the craniofacial skeleton (DeLeon, 2007) or compression of the skull base (Rewekant, 2001). Those indicators recording stressful events on the skeleton for the rest of an individual’s life are particularly important, and such unerasable markers can also be found on the axial skeleton.
Human vertebrae, especially the thoracic and lumbar vertebrae, are bony elements with specific growth dynamics and have the ability to capture stressful episodes in early childhood. This is due to the fact that before birth and in the first years of life the nervous system develops faster than any other apparatus and the bony structures surrounding these tissues must match their growth pattern (Goodman and Armelagos, 1989). The vertebral neural canal (VNC) surrounds the spinal cord, and the most rapid growth of its lumbar part occurs between 12 and 32 weeks in utero, with the anteroposterior canal diameter of vertebrae L1–L4 already reaching 70% of adult dimensions at birth (Jeffrey et al., 2003). After birth, the neurocentral synchondroses remain open and allow the vertebral foramen to enlarge around the growing spinal cord until the age of 6 years when neurocentral fusion is completed. It is therefore obvious that the VNC exhausts its growth potential very early and both maternal and early childhood stressors may affect its size throughout the rest of life (Porter and Pavitt, 1987; Papp et al., 1994; Schaefer et al., 2009). The growth of vertebral bodies in height occurs in a different way, increasing between birth and 5 years of age, followed by a period of quiescence between 5 and 10 years until the adolescent growth spurt between 10 and 13 years (in girls) and 12 and 15 years in boys (Diméglio and Canavese, 2012; Morlesin et al., 2023). Due to these specific growth dynamics of vertebral bodies, a transient period of growth inhibition can be followed by so-called catch-up growth when living conditions improve (Prader et al., 1963). This is characterized by growth velocity above the normal limits for age and often erases the consequences of former stressors recorded in reduced sizes (Hermanussen, 2010).
The first attempts at revealing early childhood stress inscribed in VNC features began in the 1980s. From the very beginning, the association between evidence of growth stunting in early life, inferred through variation in the size of the VNC, and shortened lifespans has been explored. It was shown that a small VNC was significantly associated with decreased lifespan of adult Mississippian maize horticulturalists (950–1300 A.D.) (Clark et al., 1986). Likewise, Porter et al. (1994) demonstrated that a small VNC is a marker of a generalized developmental disturbance and is associated with impairment of adult health. Watts contributed several studies, starting with research confirming a link between small VNC size and decreased lifespan in adult medieval English population (10th–15th century A.D.) (Watts, 2011). In a further study, she included multiple stress indicators and chronologically distinct skeletal series, reaffirming the long-term sequelae of health insults experienced during childhood development (Watts, 2013a). The latest VNC-focused research has then revised the age of growth completion separately for the anteroposterior and transverse dimensions and has adjusted the attainment of adult size at a later stage for the latter (Watts, 2013b). Newman and Gowland (2015) implemented vertebral measurements (vertebral body height and transverse diameter of the canal) from non-adult vertebrae as a new methodology for the identification of growth disruption in past populations. The same study reaffirmed that VNC size reduction was associated with an early age-at-death for postmedieval English sites. The results of a study by Amoroso and Garcia (2018) deviate from previous ones, as they found no effect on longevity in individuals with canal growth stunting in a modern Portuguese collection. A recent study by Corron et al. (2023) provided large-scale quantification of VNC variability across ontogeny in a contemporary sample of subadults and confirmed that anteroposterior diameter growth ends during childhood while transverse diameter growth may slightly increase before ending in adolescence.
Considering all these findings, we chose to analyse VNC features to better understand the living conditions in the medieval silver-mining centre of Kutná Hora (Czech Republic). In the Middle Ages, this local silver ore district was one of the largest producers of silver not only in the Czech lands, but also in the whole of Europe (Pauliš, 2000). During the boom of Kutná Hora mining, in the 13th–16th centuries, the centre had no parallels in Central Europe and its importance for the country’s economy was absolutely paramount. During the entire existence of mining in this area, approximately 1346 tonnes of silver were obtained (Malec and Pauliš, 2000). The discovery of silver and the turbulent years of prosperity that followed completely changed human society, its behaviour, and its environment. We know that on a local scale, any kind of mining significantly changed the ecological situation in the region in medieval times, especially through massive deforestation (Boroń and Rozmus, 2014; Hrubý et al., 2019). Another serious threat was the pollution caused by mining/smelting operations, which introduced high concentrations of heavy metals into the soil, water, and air near the miners’ homes (Štefan, 2013; Cembrzyński, 2019).
Every member of the community was involved either directly or indirectly in the exploration and extraction of silver. The people who lived, laboured, and died here constituted a highly specific community fundamentally different from the medieval agricultural population and the burghers. These people were drawn together by the need for employment or the desire to get rich; their careers were often dizzying, both on the way up and on the way down (Altová, 2006, 2010). The local population is believed to have reached 8000–10000 inhabitants by the end of the 14th century and perhaps even as much as 18000 by around 1500 CE (Molenda, 1976; Macek, 1992; Maur, 1998). Regardless of the position they held, all persons who lived within this area were exposed to health risk factors related to overcrowding and heavy metal contamination. For socially lower-class individuals, adversity within the urban environment may have also included malnutrition, economic oppression, poverty, and heavy workloads (Bogin et al., 2007). On top of that, infection was an ever-present hazard in medieval sites, but particularly in the crowded conditions of the urban centres (Shapland et al., 2016; Brødholt et al., 2022). On the other hand, miners’ autonomy, their privileged status, access to reasonable diets, material benefits, and incomes resulting from mining work could have counterbalanced some of these effects and could have rendered life more tolerable (Nováček, 2001; Cembrzyński, 2019; Geltner, 2021, 2023).
However, until recently, there were no skeletal series of sufficient size available for the study of living conditions in medieval Kutná Hora. That changed in 2016 with the discovery, in the Kutná Hora suburb of Sedlec, of a burial ground unearthed at the Cemetery Church of All Saints with Ossuary. Two distinct groups of individuals were revealed: one buried in individual earthen graves (13th–16th century) and a second buried in famine- and plague-assigned mass burials (dated to the first half of the 14th century) (Frolík, 2017, 2018). In the adult subsample, a deviation of the sex ratio was identified (SR = 1.49), which was skewed in favour of men and could have possibly been associated with the inflow of men migrating to the town for labour opportunities (Brzobohatá et al., 2023). Carbon and nitrogen isotope values from bones revealed that the diet of miners and allied professions living and working in Kutná Hora was based on C3 plants and was of a good quality in terms of the relatively high proportion of animal products (Drtikolová Kaupová et al., 2023). We have also focused on indicators of non-specific stress in a pilot study of 68 individuals from famine-assigned mass graves. In this size-limited sample we found an above-average frequency of cribra orbitalia and low frequencies of dental enamel hypoplasias and tibial periostitis (De Lépinau et al., 2021). The dating of the uncovered burial ground corresponds to the period when Kutná Hora prospered and reached European importance, but at the same time, the city succumbed to at least two severe mortality crises.
The first group of analyses tested possible differences of the VNC size between males and females. Because VNC size studies have recorded varying conclusions regarding sexual dimorphism of VNC parameters, this step was needed to verify the necessity of testing sex-separated groups. Secondly, early-life growth disruption is an example of a contributor to selective mortality that can increase the risk of mortality at later stages of life. Based on previous research, we hypothesized that there would be a decrease in VNC parameters discernible in individuals who died in young adulthood compared to mature adulthood irrespective of the context of their burial. Thirdly, surviving early-life disruptions could have weakened future responses to disease and starvation when Kutná Hora residents faced an introduced pathogen or instance of famine. In the last hypothesis we formulated, we expected that individuals recovered from mass burials would display stunted VNC size compared with individuals buried in individual (non-catastrophic) graves.
The archaeological site of Kutná Hora–Sedlec is located in Central Bohemia, 70 km east of Prague (Figure 1). The Institute of Archaeology of the Czech Academy of Science conducted rescue archaeological surveys at the Cemetery Church of All Saints with Ossuary from 2016 to 2018, preceding the static securing of the building. In the graveyard surrounding the church, both individual and mass graves were documented (32 mass graves with 956 skeletons and 861 individual burials; 1817 skeletons in total). The chronology of mass burials at the ossuary is based on the stratigraphic observation of two levels of these graves. The younger stratigraphic level has been damaged by the ossuary walls. The ossuary was built, according to art-historical literature, after 1380 (Poche, 1980). Assigning a younger level of graves to the victims of the plague epidemic from 1348 to 1350 is based on the finding of Prague groschen of Czech King John of Luxembourg (1310–1346) in two graves. In one case, these are the last mintings of this king dating back to 1346. We link the older level of the mass graves with the report in the Zbraslav Chronicle (Chronicon aulae regiae) in 1318 on the famine and the burial of its victims in front of the Sedlec Gate of Kutná Hora (Emler, 1884) (this assumption has already been verified by initial radiocarbon dating of the bones collected from six graves). The remainder of the graves, i.e. single inhumations, are archaeologically dated to the 13th–14th centuries and the 14th–16th centuries, respectively (Brzobohatá et al., 2019). Material artefacts recovered from the site consisted primarily of buckles, rings, pottery shards, and coins (Frolík, 2017, 2018). The cemetery location, grave construction, burial treatment, and poor grave material indicate that those interred there included general citizens of non-elite status.
Map of the Czech Republic showing the location of the archaeological site of Kutná Hora–Sedlec with the Cemetery Church of All Saints with Ossuary.
Only sexed adult individuals (˃18 years) with a defined age category were examined in this study. A skeleton was classified as an adult if all epiphyses of the long bones had fused prior to death. The age at death of adult individuals was estimated based on the degree of dental attrition and changes in commonly assessed articular facets (Lovejoy, 1985; Brooks and Suchey, 1990; Schmitt, 2005; Calce, 2012). Sex was determined using a suite of cranial and pelvic traits with an emphasis on the latter (Ferembach et al., 1980; Brůžek, 2002; Murail et al., 2005). Furthermore, inclusion in the sample was conditional on: (1) the acceptable to excellent preservation of the thoracic and lumbar spine enabling reliable determination of the individual vertebrae within the vertebral column; and (2) the absence of pathologies and anatomic variants such as supernumerary vertebrae. In total, 207 individuals met these conditions, comprising 119 males and 88 females. Individuals were assigned to subsamples based on the different burial contexts from which they were recovered. The mass grave sample provided 136 skeletons (classified as the MASS subsample) and the non-catastrophic burial assemblage provided 71 males and females (classified as the INDIVIDUAL group). Table 1 depicts the final sample demographics divided by sex and burial context. Skeletal macroscopic age-at-death estimation techniques usually lead to a subdivision of the adults into 10-, 20-year, or longer intervals. In order to facilitate comparative analyses between younger and older adult individuals, skeletons were lumped into broader arbitrary categories using the midpoint of the age-at-death range. Those individuals, whose midpoint of the age-at-death range reached a value from 18 to 39 years were classified into a YOUNG ADULTS category and those with a midpoint reaching 40 or more were categorized into an OLDER ADULTS group. Skeletal remains from Kutná Hora–Sedlec are deposited in the depository of the National Museum in Prague–Horní Počernice.
Sample composition by sex, burial context and age-at-death category
| Dataset | Recovered individuals | ||||
|---|---|---|---|---|---|
| Males (YOUNG) | Males (OLDER) | Females (YOUNG) | Females (OLDER) | Total | |
| MASS | 45 | 34 | 26 | 31 | 136 |
| INDIVIDUAL | 15 | 25 | 15 | 16 | 71 |
| All | 60 | 59 | 41 | 47 | 207 |
For each vertebra (Th10–L5) three osteological measurements were determined using standard calipers (recorded to the closest 0.1 mm). The maximum anteroposterior (AP) diameter was measured from the posterior portion of the vertebral body to the utmost opposite point of the neural canal anterior to the spinous process. The transverse (TR) diameter was measured as the maximum distance between medial surfaces of the left and right pedicles. Both measurements were made from the superior view of all vertebrae (Watts, 2011). Anterior body height (BH) was measured following the protocol of Klein et al. (2015) as the linear distance between the upper and lower plates in the medial sagittal plane at the ventral side of the vertebral body (Figure 2). For this study, we used adult maximum femur length as a proxy for body size. The maximum length of the femur was measured in right femora using a standard osteometric board and recorded to the nearest millimetre. All measurements were taken by the first author. The statistical analyses employed to address the research questions started with Shapiro–Wilk normality tests to check for normal distribution of the datasets. Comparisons of means were performed by independent two-sample t-test if the data passed the normality test (the non-parametric Mann–Whitney test was used for the small portion of the data that were not normally distributed). Pearson correlation coefficients between vertebral body height and VNC dimensions (or vertebral dimensions and individual’s femoral length) were calculated. Statistical tests were performed by PAST v. 4.03 with the accepted level for statistical significance set at 5% (P = 0.05) (Hammer et al., 2001).
Lateral view of adult lumbar vertebra with measurement location of the anterior vertebral body height (BH) (left). Cranial view of the same vertebra with anteroposterior (AP) and transverse (TR) diameters of the vertebral neural canal (right).
The first goal of this study was to investigate the existence of sex-related differences in all three vertebral dimensions (AP, TR, BH) measured in eight observed vertebrae (Th10–L5). Sex-specific means and standard deviations calculated for all diameters are provided for each vertebra in Table 2. The results of the analyses presented here reveal that 16 tested differences out of 24, i.e. the majority, showed significant differences, and that male dimensions were larger than female ones. It was also obvious that sexual dimorphism was more apparent in the thoracic than in the lumbar spine. The largest proportion of significant differences affected the BH parameter, where the male BH was greater than the female in almost all (seven out of eight) observed cases, with the exception of the L2 vertebra. The difference in the TR parameter was significant six times (out of eight monitored differences) and the difference in the AP parameter only three times (Table 2; Supplementary Figure 1). Overall, it can be said that male canals were significantly wider in both the transverse and sagittal plane, and their vertebral bodies were significantly greater in height. For this reason, further analyses were performed in sex-separated groups.
Descriptive statistics for each variable for male and female samples from Kutná Hora–Sedlec together with P-values for equality of means
| Vertebra (measurement) |
Males | Females | P (same mean) | |||||
|---|---|---|---|---|---|---|---|---|
| N | Mean | SD | N | Mean | SD | |||
| Th10 (AP) | 71 | 14.97 | 1.17 | 53 | 14.21 | 1.14 | 0.0004 | |
| Th10 (TR) | 75 | 16.64 | 1.52 | 57 | 15.77 | 1.32 | 0.0008 | |
| Th10 (BH) | 80 | 22.07 | 1.38 | 61 | 20.63 | 1.57 | <0.001 | |
| Th11 (AP) | 86 | 15.56 | 1.42 | 61 | 15.06 | 1.21 | 0.026 | |
| Th11 (TR) | 89 | 17.59 | 1.63 | 63 | 16.92 | 1.31 | 0.007 | |
| Th11 (BH) | 95 | 22.40 | 1.56 | 63 | 21.06 | 1.54 | <0.001 | |
| Th12 (AP) | 96 | 16.50 | 1.44 | 69 | 16.11 | 1.38 | 0.088 | |
| Th12 (TR) | 100 | 20.12 | 1.82 | 71 | 19.35 | 1.63 | 0.005 | |
| Th12 (BH) | 99 | 23.96 | 1.82 | 72 | 22.97 | 1.64 | <0.001 | |
| L1 (AP) | 108 | 16.26 | 1.38 | 75 | 16.24 | 1.28 | 0.921 | |
| L1 (TR) | 112 | 21.36 | 1.66 | 78 | 20.64 | 1.37 | 0.001 | |
| L1 (BH) | 112 | 25.28 | 1.61 | 79 | 24.56 | 1.36 | 0.001 | |
| L2 (AP) | 109 | 15.28 | 1.49 | 81 | 15.46 | 1.41 | 0.388 | |
| L2 (TR) | 111 | 21.46 | 1.63 | 84 | 20.84 | 1.44 | 0.006 | |
| L2 (BH) | 115 | 26.07 | 1.62 | 83 | 25.72 | 1.33 | 0.103 | |
| L3 (AP) | 106 | 14.38 | 1.54 | 72 | 14.34 | 1.59 | 0.865 | |
| L3 (TR) | 110 | 21.43 | 1.65 | 83 | 20.84 | 1.51 | 0.011 | |
| L3 (BH) | 109 | 26.92 | 1.65 | 84 | 26.29 | 1.33 | 0.004 | |
| L4 (AP) | 99 | 14.77 | 1.68 | 73 | 14.45 | 1.75 | 0.221 | |
| L4 (TR) | 107 | 21.52 | 1.78 | 80 | 21.23 | 1.71 | 0.271 | |
| L4 (BH) | 110 | 27.41 | 1.67 | 80 | 26.08 | 1.47 | <0.001 | |
| L5 (AP) | 74 | 15.64 | 1.81 | 67 | 15.01 | 1.91 | 0.045 | |
| L5 (TR) | 86 | 24.45 | 2.68 | 69 | 23.75 | 2.02 | 0.074 | |
| L5 (BH) | 90 | 28.15 | 1.88 | 73 | 26.45 | 1.41 | <0.001 | |
Significant differences are marked in bold. N, number; SD, standard deviation; AP, anteroposterior vertebral neural canal diameter; TR, transverse vertebral neural canal diameter; BH, anterior vertebral body height.
To test whether disruptions in the early-childhood or all growth periods affect adult mortality, t-tests were used to compare variation in AP, TR, and BH between arbitrary age-at-death categories (YOUNG ADULTS versus OLDER ADULTS) for each sex. When the mean values were compared, no significant results were found in the female dataset, and it can be concluded that women who died in younger adulthood showed the same vertebral dimensions as women who died later, when middle aged or elderly. There was no signal that would indicate differences in experiencing early childhood stress in any of the examined groups (Table 3). On the other hand, several significant differences were found in the group of males, and their occurrence increased in the caudal direction. Of the nine significant differences found, a total of three related to the AP dimension and six related to the TR dimension. In all of these cases, smaller AP and TR dimensions were found in the cohort of males who died in young adulthood compared with the group that included individuals who died in later adulthood. The complete absence of significant differences in the BH dimension (YOUNG ADULTS versus OLDER ADULTS males) indicated that males from the younger adult group went through stressful events only in early childhood and later improvement in conditions allowed catch-up growth of this particular parameter (Table 4; Supplementary Figure 2).
Descriptive statistics for each variable and P-values for equality of means for the female subsample divided by age-at-death
| Vertebra (measurement) |
YOUNG females | OLDER females | P (same mean) | |||||
|---|---|---|---|---|---|---|---|---|
| N | Mean | SD | N | Mean | SD | |||
| Th10 (AP) | 23 | 14.47 | 1.08 | 30 | 14.01 | 1.17 | 0.095 | |
| Th10 (TR) | 26 | 15.57 | 1.31 | 31 | 15.93 | 1.34 | 0.312 | |
| Th10 (BH) | 29 | 20.96 | 1.63 | 32 | 20.34 | 1.47 | 0.061 | |
| Th11 (AP) | 27 | 15.37 | 1.31 | 34 | 14.82 | 1.08 | 0.108 | |
| Th11 (TR) | 28 | 16.96 | 1.23 | 35 | 16.88 | 1.38 | 0.754 | |
| Th11 (BH) | 30 | 21.36 | 1.86 | 33 | 20.78 | 1.13 | 0.062 | |
| Th12 (AP) | 31 | 16.01 | 1.31 | 38 | 16.21 | 1.45 | 0.459 | |
| Th12 (TR) | 32 | 19.06 | 1.58 | 39 | 19.58 | 1.64 | 0.211 | |
| Th12 (BH) | 34 | 23.26 | 1.89 | 38 | 22.71 | 1.35 | 0.141 | |
| L1 (AP) | 33 | 16.31 | 1.15 | 42 | 16.19 | 1.38 | 0.934 | |
| L1 (TR) | 35 | 20.41 | 1.43 | 43 | 20.83 | 1.31 | 0.211 | |
| L1 (BH) | 36 | 24.77 | 1.51 | 43 | 24.39 | 1.21 | 0.184 | |
| L2 (AP) | 38 | 15.44 | 1.36 | 43 | 15.48 | 1.45 | 0.831 | |
| L2 (TR) | 39 | 20.76 | 1.52 | 45 | 20.91 | 1.37 | 0.562 | |
| L2 (BH) | 39 | 25.89 | 1.31 | 44 | 25.56 | 1.35 | 0.232 | |
| L3 (AP) | 34 | 14.21 | 1.47 | 41 | 14.46 | 1.71 | 0.575 | |
| L3 (TR) | 38 | 20.57 | 1.51 | 45 | 21.06 | 1.49 | 0.161 | |
| L3 (BH) | 39 | 26.38 | 1.47 | 45 | 26.22 | 1.21 | 0.458 | |
| L4 (AP) | 34 | 14.41 | 1.76 | 39 | 14.48 | 1.77 | 0.857 | |
| L4 (TR) | 38 | 21.01 | 1.81 | 42 | 21.45 | 1.61 | 0.172 | |
| L4 (BH) | 37 | 26.35 | 1.54 | 43 | 25.86 | 1.39 | 0.081 | |
| L5 (AP) | 29 | 15.03 | 1.91 | 38 | 15.01 | 1.94 | 0.699 | |
| L5 (TR) | 29 | 23.48 | 2.32 | 40 | 23.95 | 1.78 | 0.276 | |
| L5 (BH) | 31 | 26.58 | 1.51 | 42 | 26.35 | 1.34 | 0.443 | |
Significant differences are marked in bold; abbreviations as in Table 2.
Descriptive statistics for each variable and P-values for equality of means for the male subsample divided by age-at-death
| Vertebra (measurement) |
YOUNG males | OLDER males | P (same mean) | |||||
|---|---|---|---|---|---|---|---|---|
| N | Mean | SD | N | Mean | SD | |||
| Th10 (AP) | 31 | 14.74 | 1.29 | 40 | 15.15 | 1.05 | 0.293 | |
| Th10 (TR) | 34 | 16.21 | 1.22 | 41 | 17.01 | 1.65 | 0.039 | |
| Th10 (BH) | 38 | 22.01 | 1.21 | 42 | 22.14 | 1.53 | 0.522 | |
| Th11 (AP) | 43 | 15.27 | 1.43 | 43 | 15.86 | 1.37 | 0.071 | |
| Th11 (TR) | 44 | 17.25 | 1.48 | 45 | 17.93 | 1.72 | 0.057 | |
| Th11 (BH) | 47 | 22.27 | 1.62 | 48 | 22.52 | 1.51 | 0.291 | |
| Th12 (AP) | 47 | 16.44 | 1.44 | 49 | 16.55 | 1.45 | 0.641 | |
| Th12 (TR) | 50 | 19.78 | 1.48 | 50 | 20.46 | 2.07 | 0.092 | |
| Th12 (BH) | 47 | 23.97 | 1.76 | 52 | 23.96 | 1.88 | 0.901 | |
| L1 (AP) | 54 | 16.07 | 1.25 | 54 | 16.44 | 1.48 | 0.167 | |
| L1 (TR) | 57 | 20.78 | 1.39 | 55 | 21.96 | 1.72 | <0.001 | |
| L1 (BH) | 55 | 25.31 | 1.38 | 57 | 25.26 | 1.79 | 0.817 | |
| L2 (AP) | 55 | 15.09 | 1.35 | 54 | 15.48 | 1.61 | 0.105 | |
| L2 (TR) | 56 | 20.91 | 1.45 | 55 | 22.03 | 1.62 | <0.001 | |
| L2 (BH) | 58 | 25.91 | 1.61 | 57 | 26.24 | 1.63 | 0.327 | |
| L3 (AP) | 52 | 14.05 | 1.22 | 54 | 14.71 | 1.74 | 0.028 | |
| L3 (TR) | 55 | 20.91 | 1.49 | 55 | 21.96 | 1.64 | 0.001 | |
| L3 (BH) | 58 | 26.71 | 1.65 | 51 | 27.17 | 1.63 | 0.188 | |
| L4 (AP) | 49 | 14.51 | 1.51 | 50 | 15.04 | 1.82 | 0.031 | |
| L4 (TR) | 53 | 21.01 | 1.68 | 54 | 22.01 | 1.75 | 0.005 | |
| L4 (BH) | 56 | 27.14 | 1.67 | 54 | 27.71 | 1.63 | 0.078 | |
| L5 (AP) | 39 | 15.23 | 1.28 | 35 | 16.11 | 2.19 | 0.021 | |
| L5 (TR) | 44 | 23.86 | 2.61 | 42 | 25.07 | 2.65 | 0.036 | |
| L5 (BH) | 48 | 27.85 | 1.87 | 42 | 28.51 | 1.86 | 0.065 | |
Significant differences are marked in bold; abbreviations as in Table 2.
In the final set of analyses, we focused on detecting potential differences between groups divided by burial context (MASS versus INDIVIDUAL subsamples). These comparisons were also made in sex-disaggregated datasets, and here too differences were found in the reflection of early childhood stress in men compared to women. Between-burial-type comparisons performed in the female group produced varying results. Females recovered from MASS and INDIVIDUAL graves had the same AP dimensions of the vertebral neural canal in all tested vertebrae. Regarding the TR parameter, it was identical only in the vertebral segment from Th10 to L2, and significant differences were found in the lower lumbar region (from L3 to L5): here, the mean estimated from the group of MASS burials exceeded the mean calculated for the skeletons recovered from the INDIVIDUAL graves (Table 5; Supplementary Figure 3). Significant differences in the terminal size of the BH diameter were found only in Th11 and L3 vertebrae, where the mean derived from female INDIVIDUAL graves exceeded the mean calculated for the female MASS burial group. In total, only five significant differences were found throughout these burial-type female comparisons apparent as deficiencies in TR parameter (in the INDIVIDUAL burial group) and BH parameter (in the MASS burial group) (Table 5). Males recovered from MASS and INDIVIDUAL graves had the same dimensions of the vertebral neural canal and the vertebral body except for a rare case (namely the TR parameter of the tenth thoracic vertebra) where the mean derived from the group of individual burials significantly exceeded the mean calculated from the group of catastrophic burials (Table 6; Supplementary Figure 3). Supplementary Table 1 shows the correlation coefficients between measured vertebral diameters at each level (Supplementary Table 1). The coefficients between canal diameters and BH reached very low or low values (0.181–0.395) indicating a weak positive correlation between vertebral body height and VNC size along the lower thoracic and lumbar spine.
Descriptive statistics for each variable and P-values for equality of means for the female subsample divided by burial context
| Vertebra (measurement) |
INDIVIDUAL females | MASS females | P (same mean) | |||||
|---|---|---|---|---|---|---|---|---|
| N | Mean | SD | N | Mean | SD | |||
| Th10 (AP) | 14 | 14.01 | 1.17 | 40 | 14.27 | 1.13 | 0.335 | |
| Th10 (TR) | 14 | 15.21 | 1.31 | 43 | 15.95 | 1.29 | 0.087 | |
| Th10 (BH) | 16 | 21.25 | 1.84 | 45 | 20.42 | 1.42 | 0.126 | |
| Th11 (AP) | 15 | 15.13 | 1.55 | 46 | 15.04 | 1.09 | 0.931 | |
| Th11 (TR) | 17 | 16.71 | 1.15 | 46 | 17.01 | 1.36 | 0.509 | |
| Th11 (BH) | 19 | 21.84 | 1.42 | 44 | 20.72 | 1.48 | 0.014 | |
| Th12 (AP) | 19 | 16.26 | 1.09 | 50 | 16.06 | 1.49 | 0.623 | |
| Th12 (TR) | 21 | 19.38 | 1.81 | 50 | 19.34 | 1.57 | 0.862 | |
| Th12 (BH) | 23 | 23.21 | 1.24 | 49 | 22.85 | 1.81 | 0.432 | |
| L1 (AP) | 24 | 15.91 | 1.34 | 51 | 16.39 | 1.23 | 0.249 | |
| L1 (TR) | 25 | 20.28 | 1.42 | 53 | 20.81 | 1.33 | 0.143 | |
| L1 (BH) | 27 | 24.92 | 1.14 | 52 | 24.38 | 1.44 | 0.118 | |
| L2 (AP) | 31 | 15.41 | 1.51 | 50 | 15.51 | 1.35 | 0.723 | |
| L2 (TR) | 31 | 20.41 | 1.47 | 53 | 21.09 | 1.37 | 0.066 | |
| L2 (BH) | 30 | 26.13 | 1.01 | 53 | 25.49 | 1.44 | 0.059 | |
| L3 (AP) | 27 | 14.25 | 1.91 | 48 | 14.39 | 1.41 | 0.446 | |
| L3 (TR) | 31 | 20.41 | 1.47 | 52 | 21.09 | 1.49 | 0.048 | |
| L3 (BH) | 31 | 26.71 | 1.37 | 53 | 26.05 | 1.26 | 0.029 | |
| L4 (AP) | 25 | 14.24 | 2.08 | 48 | 14.56 | 1.56 | 0.187 | |
| L4 (TR) | 26 | 20.61 | 1.79 | 54 | 21.53 | 1.61 | 0.037 | |
| L4 (BH) | 29 | 26.51 | 1.51 | 51 | 25.84 | 1.41 | 0.131 | |
| L5 (AP) | 21 | 14.42 | 2.29 | 46 | 15.28 | 1.68 | 0.077 | |
| L5 (TR) | 22 | 23.01 | 1.63 | 47 | 24.11 | 2.11 | 0.033 | |
| L5 (BH) | 25 | 26.68 | 1.51 | 48 | 26.33 | 1.34 | 0.202 | |
Significant differences are marked in bold; abbreviations as in Table 2.
Descriptive statistics for each variable and P-values for equality of means for the male subsample divided by burial context
| Vertebra (measurement) |
INDIVIDUAL males | MASS males | P (same mean) | |||||
|---|---|---|---|---|---|---|---|---|
| N | Mean | SD | N | Mean | SD | |||
| Th10 (AP) | 25 | 15.08 | 1.11 | 46 | 14.91 | 1.21 | 0.569 | |
| Th10 (TR) | 26 | 17.19 | 1.74 | 49 | 16.34 | 1.31 | 0.021 | |
| Th10 (BH) | 27 | 22.18 | 1.46 | 53 | 22.01 | 1.35 | 0.614 | |
| Th11 (AP) | 31 | 15.58 | 1.36 | 55 | 15.56 | 1.47 | 0.958 | |
| Th11 (TR) | 32 | 17.91 | 1.59 | 57 | 17.42 | 1.64 | 0.181 | |
| Th11 (BH) | 32 | 22.56 | 1.61 | 63 | 22.31 | 1.55 | 0.474 | |
| Th12 (AP) | 32 | 16.12 | 1.38 | 64 | 16.68 | 1.44 | 0.071 | |
| Th12 (TR) | 32 | 20.46 | 1.93 | 68 | 19.95 | 1.76 | 0.191 | |
| Th12 (BH) | 29 | 23.75 | 1.86 | 70 | 24.05 | 1.81 | 0.461 | |
| L1 (AP) | 35 | 16.11 | 1.41 | 73 | 16.32 | 1.37 | 0.453 | |
| L1 (TR) | 37 | 21.75 | 1.51 | 75 | 21.17 | 1.71 | 0.081 | |
| L1 (BH) | 36 | 25.16 | 1.74 | 76 | 25.34 | 1.53 | 0.591 | |
| L2 (AP) | 35 | 15.11 | 1.47 | 74 | 15.36 | 1.51 | 0.415 | |
| L2 (TR) | 36 | 21.81 | 1.39 | 75 | 21.31 | 1.72 | 0.132 | |
| L2 (BH) | 37 | 26.01 | 1.59 | 78 | 26.11 | 1.64 | 0.723 | |
| L3 (AP) | 36 | 14.19 | 1.45 | 70 | 14.48 | 1.58 | 0.359 | |
| L3 (TR) | 38 | 21.57 | 1.42 | 72 | 21.36 | 1.76 | 0.512 | |
| L3 (BH) | 35 | 27.14 | 1.71 | 74 | 26.82 | 1.63 | 0.351 | |
| L4 (AP) | 31 | 14.58 | 1.62 | 68 | 14.86 | 1.71 | 0.435 | |
| L4 (TR) | 36 | 21.77 | 1.65 | 71 | 21.39 | 1.83 | 0.295 | |
| L4 (BH) | 37 | 27.71 | 1.69 | 73 | 27.27 | 1.65 | 0.205 | |
| L5 (AP) | 25 | 16.04 | 1.67 | 49 | 15.44 | 1.87 | 0.187 | |
| L5 (TR) | 28 | 25.07 | 2.17 | 58 | 24.15 | 2.87 | 0.139 | |
| L5 (BH) | 29 | 28.27 | 2.01 | 61 | 28.09 | 1.84 | 0.679 | |
Significant differences are marked in bold; abbreviations as in Table 2.
The correlation of vertebral measures to femoral length was studied both in sex-pooled and sex-divided samples. AP did not show any significant association with femoral length in the male group but showed a weak positive correlation in the sex-pooled sample (r = 0.211–0.356) and a weak to moderate positive correlation in the female group (r = 0.376–0.514). Almost all vertebrae showed a low to moderately high degree of positive correlation between TR and femoral length both in the sex-pooled and sex-divided groups (r = 0.212–0.537). As for BH, it was always significantly positively correlated with femoral length, reaching values ranging from low to high (r = 0.285–0.641) (Supplementary Table 2). These results clearly indicate that VNC dimensions have a low to moderate positive, statistically significant association with femoral length (as a proxy for body size). This implies that a certain proportion of the VNC variation found could theoretically be attributable to differences in body size and therefore we included an internal control to account for differences in individual femoral length. The t-test for equality of means demonstrated that maximum femoral length did not significantly differ between groups divided by sex, burial type, and age except for the first comparison, where INDIVIDUAL males had longer femora than MASS males (Supplementary Table 3). This fact did not have much effect on between-group comparisons of VNC size because an analogous significant difference was found only in the TR variable of Th10 vertebra (Table 6).
Based on the analyses in this study, sexual dimorphism appears to be a primary contributor to variation in the vertebral neural canal and vertebral body measurements. However, if the earlier studies were focused on the dimensions of VNC, they recorded varying conclusions regarding sex-based variation in size, and dimorphic features were not always pronounced (Clark et al., 1986; Masharawi and Salame, 2011; Watts, 2011; Newman and Gowland, 2015). Of the group of studies that, in contrast, demonstrated sexual dimorphism in VNC size, most worked with large datasets and premodern or modern skeletal material: Yaussy (2019) found consistently larger male AP and TR lumbar vertebral neural canal diameters measured in a sample of an 18th- and 19th-century English population. Amoroso and Garcia (2018, 2021) analysed a Portuguese collection (19th–20th century) and described statistically significant sex differences, with males having larger canal diameters than females, except for lumbar AP diameters where they found no sex differences. Here we find agreement with the results of our study, as our analyses also found much weaker dimorphism in the AP dimension compared with the TR, and a significant difference was identified in only one case in the lumbar spinal segment (Table 2). The same pattern was repeated in the study of a large recent Asian tomographic data sample, where sexual dimorphism was more strongly expressed in the TR dimension than in the AP. In this study, as in ours, it was also evident that TR and BH diameters were smallest at Th10 level and gradually increased to L5, while the AP dimension behaved differently: the minimum AP was found at the L3 level, enlarging both cranially and caudally (Griffith et al., 2016) (Supplementary Figures 1–3). The largest proportion of significant sex-based differences involved the BH parameter, which was to be expected, as dimensions capturing the height of the vertebral body are among the best predictors of sex in a group of vertebral measurements (reviewed in Rohmani et al., 2021).
In the next step, we took advantage of the unique property of the VNC of adult individuals, which can serve as a potential repository of information about the health and nutrition of an individual over his or her early childhood (Clark et al., 1986; Porter et al., 1994). The second hypothesis tested was that individuals who experienced stress during early growth faced increased mortality at earlier adult ages than individuals who did not experience measurable disruptions to VNC growth. This hypothesis was partially supported by the results collected from the male subsample: YOUNG ADULT males (18–39 years) from Kutná Hora–Sedlec exhibited significantly smaller VNC diameters than those who survived to an older age (OLDER ADULT males, with a midpoint of age-at-death interval reaching 40 years or more). These significant differences were found mainly in the lumbar region of the spine and twice as often in the TR dimension as in the AP dimension. Interestingly, significant differences were found only in those vertebral neural canal dimensions that complete growth earlier in the developmental trajectory. No observable differences between YOUNG ADULT and OLDER ADULT males were found in the BH dimension, suggesting similar overall growth profiles of both groups that differed only in the early childhood stress profiles (inferred from AP and TR diameters). The lack of statistical significance in BH comparisons indicates that these early stress events were probably later erased from vertebral body height by catch-up growth. Several significantly smaller AP and TR diameters in males who died in young adulthood are reflective of different childhood experiences compared to men who lived to a greater age. In particular, their TR dimensions indicate that the males from the YOUNG ADULT age-at-death group faced early-life constraints that resulted in shorter lifespan. Similar to previous work, we confirmed the link between small VNC size and early mortality (Clark et al., 1986; Watts, 2011, 2015) and that TR measurements were more extensively affected than AP (Watts, 2011).
The fact that women divided into YOUNG ADULT and OLDER ADULT age-at-death groups showed identical stress profiles may have several causes. First, both female subgroups were stressed to the same extent and the female population from medieval Kutná Hora was more homogeneous than males at least as far as early childhood is concerned. Another possibility is that, hypothetically, strong selective mortality of female individuals with small VNC size in childhood/adolescence could have resulted in a uniform adult female sample with no apparent deviation in any age-at-death subgroup. The lack of any significant difference between female age-at-death subsamples could also be interpreted as the result of higher environmental buffering of the female body and as a support for the hypothesis of greater male sensitivity to physiological stress (both disease-induced and nutritional). However, the complex cultural environment in which humans lived and still live limits the ability to test the hypothesis and no consensus has yet been reached on the issue of sex differences in environmental sensitivity during the postnatal growth period. Moreover, the interpretation of sex differences in past stressed populations is complicated by the possibility that one sex, usually boys, may have been treated better than the other (Stinson, 1985; Guatelli-Steinberg and Lukacs, 1999; Mattsson, 2021).
The last objective of the study was to explore whether VNC diameters and BH varied with burial context and whether individuals with reduced VNC or BH size were more likely to die in times of mortality crises when facing deadly pathogens and/or food shortages. It was expected that individuals recovered from MASS graves would display stunted VNC when compared with individuals buried in INDIVIDUAL (non-catastrophic) graves. The only significant difference found in the group of men and the five identified significant differences in the group of women indicate that the relationship between early life stress and the risk of succumbing to plague/unknown pathogen or famine is very weak (in females) or non-existent (in males). Contrary to expectations, we recorded three cases of significantly smaller TR diameters in females recovered from INDIVIDUAL graves who may have been subjected to slightly greater early childhood stress compared with the MASS group. Two significant differences recorded in vertebral body height provided a predicted stress profile with BH smaller in the MASS female subgroup. Only in this case could we tentatively confirm our assumption, but frailty of these females was linked to adverse environmental and poor nutrition factors operating throughout the whole developmental period, not only in early childhood. Overall, the signal that was revealed in the last group of analyses was very weak and serves rather as a stimulus for further investigation of skeletons buried in mass graves. At this point, a relevant limitation should also be mentioned regarding the line between catastrophic and non-catastrophic datasets, which is not as clear as it seems. As mortality crises started slowly, then escalated and subsequently gradually came to an end, some of the catastrophic victims, the first and the last ones, could also be buried in individual graves. This has been shown recently in a study by Cessford et al. (2021), who identified skeletons in medieval cemeteries in Cambridgeshire that were positive for the plague bacterium yet were interred in a normative way.
Medieval mining communities lived in an environment characterized by a unique set of ecological and biocultural conditions where multiple cultural and environmental factors were operating synergistically or antagonistically. The range of biological and cultural sources of adversity was probably large, and the population facing them was quite heterogeneous. Of particular interest is our finding that BH did not significantly differ (with two exceptions) in comparisons of age- and burial-context-separated males and females, suggesting equal stress profiles of the contrasting groups throughout the growth period (YOUNG ADULTS versus OLDER ADULTS and MASS versus INDIVIDUAL burials). In contrast, VNC diameters provided valuable information on the early life process of growth and captured episodes of stress occurring during a limited and well-defined sensitivity window. AP and TR retained evidence about health stressors during early childhood and, due to these stress episodes, males with stunted VNCs were less likely to survive into mature adulthood. Conversely, females, whether they died in young or mature adulthood, appear to have experienced the same conditions during early growth (or they were able to better buffer against them). The association between early-life stress and the risk of succumbing to plague/unknown pathogen or famine was inconclusive in both males and females. Future research avenues worth exploring include investigating the following: the living conditions of women settled in medieval mining centres, who attracted far less attention from the chroniclers than men, their overall life histories, childhood dietary patterns, residential mobility, and inter-site comparisons with medieval skeletal series distinct in terms of biological and cultural factors.
This study was supported by the Czech Science Foundation (project no. GA21-09637S).
Hana Brzobohatá: conceptualization, methodology, investigation, data curation, project administration, funding acquisition, writing original draft. Jan Frolík: project administration, formal analysis, data curation, providing archaeological context, writing original draft. Filip Velímský: providing archaeological context, validation, visualization.
