Bioarchaeology of Past Epidemic- and Famine-Related Mass Burials with Respect to Recent Findings from the Czech Republic

Irrespective of the reason for breaking usual burial customs, mass graves represent a valuable archive of population data over a short period, and thus offer a vast amount of information for bioarchaeological research. Herein, we present a selective review of research on past epidemic and famine die-offs and of new interdisciplinary approaches in this field of study. We summarize the discoveries of epidemicand famine-related graves that are temporally and spatially restricted to the medieval/early modern Czech territory, paying special attention to recently unearthed mass burials in Kutná Hora-Sedlec. These burial pits are historically and contextually associated with a famine in the early 14th century and with the Black Death in the mid-14th century. To our knowledge, they represent the largest set of medieval mass graves not only in the Czech Republic but also on a European scale. IANSA 2019 ● X/1 ● 79–87 Hana Brzobohatá, Jan Frolík, Eliška Zazvonilová: Bioarchaeology of Past Epidemicand Famine-Related Mass Burials with Respect to Recent Findings from the Czech Republic 80 samples have shown an increased mortality in non-adults (Geber, 2014), and chronologically younger datasets indicate increased mortality at both extremes of the age spectrum, i.e. children and in elderly persons (Morgan, 2013). As for the epidemic mortality, the most lethal killer – plague – was not selective for sex and male/female ratios of plague burial grounds did not significantly differ from preand post-epidemic cemeteries (Signoli et al., 2002; De Witte, 2009). Less frequently, excess female mortality was documented in both urban and rural contexts (Curtis, Roosen, 2017). Another of the factors explored and potentially impacting plague mortality profiles was ageat-death, and DeWitte (2010a) has shown that older adults showed somewhat higher risks of dying during the epidemic compared to the younger. In general, two different types of mortality can be found in skeletal assemblages: catastrophic and attritional (Margerison, Knüsel, 2002). A high percentage of infant deaths, a low number of adolescent deaths, and an increasing mortality rate throughout adulthood would be consistent with attritional (normal) mortality, while an increased risk of death occurring in all age categories reflects a short-term catastrophe (Gowland, Chamberlain, 2005). If the population was affected by an epidemic, deceased individuals were often buried in mass graves because there was not the time, nor space to bury them individually. If the epidemic killed people indiscriminately regardless of age and sex, then the mass graves would represent an unbiased sample of the population. However, the results of different studies (e.g. DeWitte, 2010b; Galanaud et al., 2015; Crespo, Lawrenz, 2016) have shown that this is not the case, but rather, that susceptibility to death varies during sudden events such as epidemics, which have been referred to as heterogeneity in frailty (Wood et al., 1992). Recent research has indicated that one of the worst demographic crises, the Black Death, caused selective mortality and removed the frailest of the population (DeWitte, 2016). The concept of frailty, defined as a state of decreased resistance to stressors (Fried et al., 2001), has been discussed in several recent bioarchaeological studies (DeWitte, Wood, 2008; DeWitte, 2010b). Factors typically used to evaluate frailty in epidemiological research are generally not observable in skeletal remains. In archaeological populations, only skeletal and dental indicators of stress indicate pathological conditions in an individual. Marklein et al. (2016) proposed a method based on assessing the frailty of living populations applicable to bioarchaeological populations, the skeletal frailty index (SFI). This method provides a frailty score for everyone in a population based on the presence or absence of 13 skeletal and dental indicators. This method should provide a better understanding of the overall health of past populations rather than simply measuring mortality (Marklein et al., 2016). Demographic composition and indicators of skeletal stress are essential for better understanding health and mortality. By comparing the prevalence of stress indicators (e.g. cribra orbitalia, linear enamel hypoplasia, periosteal new bone formation) in individuals buried in attritional (normal) and mass graves, the level of stress and risk of death can be determined. Higher prevalence of stress lesions would be expected in mass graves. However, the relationship between stress lesions and mortality is not straightforward, demonstrating the osteological paradox phenomenon (Wood et al., 1992; DeWitte, Stojanowski, 2015). The presence of stress lesions does not necessarily mean that the individual was healthier compared with those without lesions, but rather, some individuals without stress lesions died before the stress was reflected in the skeleton. The most detectable skeletal markers require several weeks to form; thus, we can assume that individuals with lesions must have at least survived this long. Bone is slower to respond to the effects of stress than soft tissue. Therefore, the presence of stress indicators indicates severe or prolonged stress. Instead of comparing the prevalence of skeletal stress indicators, they should be evaluated in terms of mortality and their effect on survivorship (Temple, Goodman, 2014). In the case of mass graves, cultural or historical context can help to understand whether individuals with a higher prevalence of stress were frailer. Although the demographic composition of a population suffering a disease epidemic differs from that of a non-epidemic population, some factors can influence the age distribution of examined samples. Taphonomic factors that influence infant skeletal remains can make them invisible in the archaeological record, consequently biasing the final distribution. When historical and cultural conditions are unknown and only demographic composition is available as evidence of a demographic crisis, differences in skeletal preservation may distort results to resemble attritional mortality (Margerison, Knüsel, 2002; Kyle et al., 2018). Ageing presents further problems in bioarchaeological research. Poorly preserved skeletons, systematic underestimation of old individuals, or circumstances affecting skeletal aging, are some of the factors that complicate the estimation of age at death of adults (Cave, Oxenham, 2016). Furthermore, inconsistency in the use of age-estimation methods causes problems when comparing burial grounds, or their apparent normal mortality (Bramanti et al., 2018). Nevertheless, by combining methods from social and biological sciences in the study of historical mass graves, we can more thoroughly interpret the information held in the bones and, thanks to this transdisciplinary approach, better reconstruct daily life in times of catastrophes. 2. Difficulties in retrospectively diagnosing infectious diseases Previous studies of ancient disease episodes have largely relied on historical and archaeological data alone, such as skeletons, mummified remains, ancient texts, church records, burial registers, and art works (Mitchell, 2011; Signoli, 2012; Smith et al., 2012). However, the most common infections of these times are osteologically invisible, and written records are often inaccurate. Thus, it is not possible to come to a IANSA 2019 ● X/1 ● 79–87 Hana Brzobohatá, Jan Frolík, Eliška Zazvonilová: Bioarchaeology of Past Epidemicand Famine-Related Mass Burials with Respect to Recent Findings from the Czech Republic 81 modern biological diagnosis for many past epidemics. By medieval times most of the acute infectious diseases were universal in the Old World and had settled into distinct cycles of epidemics, mainly affecting young children (Crawford, 2007). Considering key environmental and epidemiological factors of medieval towns, nearly all microbial and viral transmission routes were facilitated by poor sanitation conditions, contaminated water, and overpopulation. Although many of the worst pre-industrial epidemics appear to have been caused by the bubonic plague, the range of epidemics that are referred to as “plagues” is much larger (Alfani, Murphy, 2017). The causes of epidemics referred to as “peste” or “pestilential” by contemporaries must be investigated separately because it cannot be assumed that a ‘‘plague’’ in one place was due to the same specific microbial agent as those in other places, even during the Black Death (Carmichael, 2008). In particular, populations weakened by malnutrition/starvation could have easily succumbed to influenza, typhus, dysentery, smallpox, typhoid fever, relapsing fever, or another highly-transmissible pathogen (Smith et al., 2012; Andam et al., 2016; Guellil et al., 2018). For a long time, the most interesting topic concerning the scholars researching historic epidemic assemblages has been determining the causative organism of the bubonic plague (Beauchamp, 2012). The most likely pathogen to account for the plague epidemics is Yersinia pestis. The actual aetiology of this disease has long been controversial, and a group of researchers have argued in favour of other potential microbial agents of the medieval episodes of great mortality. Alternative hypotheses included bacillus anthracis (Twigg, 1985), a filovirus, or a pathogen that is now extinct (Scott, Duncan, 2001; Cohn, 2003; Duncan, Scott, 2005). They argued that: the differences between the Black Death and current manifestations of the plague are too great to have the same aetiology (Cohn, 2002); the epidemiological dynamics of the medieval Black Death based on historical records were consistent with a viral pathogen spreading as an aerosol or through direct contact between persons (Bossak, Welford, 2009). Other inconsistencies have been pointed out by sceptics, including those between the clinical and epidemiological characteristics of pla