Temporal changes in childhood health during the medieval Little Ice Age in Denmark

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Abstract

Objective

This study examines the evidence of three skeletal markers of childhood health that leave permanent observable changes in the adult skeleton during two climate events, the Medieval Warm Period (MWP) and the Little Ice Age (LIA) that occurred in the medieval period (1050–1536 CE).

Material

A total of 241 adult skeletons from the Danish medieval period were included.

Methods

Linear enamel hypoplasia (LEH) was examined macroscopically. Harris lines (HL) and infectious middle ear disease (IMED) were examined from CT imaging. The skeletons were segregated by the mortuary pattern of arm position that coincidentally changes between the MWP to the LIA.

Results

LEH and IMED increase in frequency from the MWP to the LIA while there is a reverse trend for HL.

Significance: This is the first study that examines childhood health as reflected on skeletal remains of adults using a combination of CT imaging and macroscopic examination for temporal changes in the medieval period.

Limitations

The study did not include any sub-adults due to limitation of methods, i.e. the method of IMED is not yet developed to assess sub-adults. Neither was time-of-occurrence for the skeletal marker included as there is conflicting information from different methods for HL and neither has it been developed yet for IMED.

Suggestions for further research

A sample of sub-adults from both time periods could be compared by sub-adult mortality, as well as for differences in the timing of skeletal age markers.

Introduction

In Denmark, the medieval historic period commenced about 1050 CE and continued until 1536 CE upon the accession of King Christian III and the adoption of Lutheranism (Ingesman et al., 2001; Lockhart, 2007). The Medieval Warm Period (MWP) began in Denmark about 1150 CE (Augenti and Gilchrist, 2011; Barber and Chambers, 2019). This period contributed to a rise in population levels (Augenti and Gilchrist, 2011) with the highest population number occurring during the early 13th century (Hyldgaard, 2012). The end of the MWP was followed by the onset of the Little Ice Age (LIA) around 1300 CE (Augenti and Gilchrist, 2011; Fagan, 2000). The colder winters were followed by wet summers, which affected the length of the growing season and the amount of pre-harvest drying time ultimately leading to crop failures (Tkachuck, 1983). Shortages of grain and fodder resulted in famine and malnutrition for people. This was particularly so in 1294–5 CE, 1315–18 CE and 1437–40 CE (Gamble, 2015). Concurrently, the plague arrived in Denmark in 1350 CE, with continued outbreaks for several centuries, until 1711 CE. It has been estimated that up to 50% of the population in Europe died of the plague (Gamble, 2015). Together, these events lead to a significant population decline during the 14th century (Yoder, 2006).

Also noteworthy for the medieval period in Denmark, was the prevalence of leprosy. The disease was present from the very start of the medieval period in both urban and rural communities of Denmark (Boldsen, 2009). Skeletal evidence suggests that up to 40% of the Danish population was infected with leprosy (Boldsen, 2009). By ca. 1400 CE, leprosy appears to have been eliminated from the major towns and only few sufferers have been detected around 1550 CE (Boldsen, 2009). The population decline led to better living conditions later in the medieval period, particularly for the rural populations. This was due to increase demand for labour and, hence, increased wages, as well as cheaper food (Hybel and Poulsen, 2013; Yoder, 2006). When the medieval period in Denmark ended with the Reformation in 1536 CE, the country had reverted to a more environmentally stable period and a new epoch began with the Renaissance (Ingesman et al., 2001).

Few studies have examined childhood health for temporal changes specifically reflecting the climate shift of the LIA, in medieval Denmark (Gamble, 2015; Yoder, 2006) although studies on temporal changes have been published on other subjects such as diet (Yoder, 2010), prevalence of leprosy (Boldsen, 2009), trauma (Milner et al., 2015), and pattern of dental attrition (Boldsen, 2005). This is the first study that examines childhood health as reflected on skeletal remains of adults using a combination of CT imaging and macroscopic examination.

During the medieval period, Scandinavia was rather unique in how upper arms were fairly consistently placed for burial enabling the identification of three time periods (Kieffer-Olsen, 1993; Redin, 1976). This allows bioarcheological investigations of large cemetery samples to document temporal changes using this specific mortuary customs (Jantzen et al., 1994; Kieffer-Olsen, 1993; Redin, 1976). A recently published study of childhood health during the Danish medieval period with a focus on comparing urban and rural skeletal populations effectively used the same cemetery samples (Primeau et al., 2018). This study re-analyzed the same material temporally with a focus on the possible significant impact of MWP and LIA climatic changes. This study contributes to understand the interaction of environmental and climatic fluctuations in the expression of lasting osteological changes in adult skeletons.

Studying health and growth during childhood is of interest because it conveys important information about the general living conditions experienced by past populations. Children, because of their growth and development plasticity, are arguable more vulnerable to the negative effects of adverse living conditions than adults and as such can act as sensitive indicators of population health (Halcrow and Tayles, 2011). Several problems arise when studying health during the childhood years based on the sub-adults in archaeological samples, one being an age-skewed population of non-survivors. Surviving sub-adults lived on to become adults. This means that childhood health is often reduced to looking at childhood mortality (conversely survivorship into adulthood). Also, it is well known that sub-adult skeletons may not be retrieved fully in archaeological excavations due to differing burial customs for infants and children, as well as preservation from taphonomic processes and recovery practices (Guy et al., 1997; Lewis, 2007; Murphy, 2011). Adult skeletal material, as sub-adults who survived childhood, may provide data to better understand childhood health.

We chose three skeletal markers of demonstrable utility in assessing sub-adult health: linear enamel hypoplasia, Harris lines and specific bone changes following episodes of childhood middle ear infection (i.e., otitis media) (Primeau et al., 2018). The markers are permanent, and thus recordable in the adult skeletons (Ameen et al., 2005; Egawa et al., 2001; Homøe and Lynnerup, 1991; Homøe et al., 1992, 1996; Larsen, 2015; Roberts and Manchester, 2005).

Harris lines (HL) and linear enamel hypoplasia (LEH) have frequently been used within paleopathology, although less so for the former (Roberts and Manchester, 2005; Larsen, 2015; Lewis, 2017). The third marker indicative of chronic or recurrent infectious middle ear disease (IMED) is certainly informative (Homøe and Lynnerup, 1991; Homøe et al., 1992, 1996; Krenz-Niedbała, 2017; Qvist and Grøntved, 2000, 2001), but is rarely used, probably due to the need of CT equipment although the standard X-ray can also be used (Homøe and Lynnerup, 1991; Lynnerup et al., 2000). These three markers all have a nonspecific, multifactorial origin, reflecting general living conditions during childhood rather than specific diseases (Ameen et al., 2005; Casselbrant and Mandel, 2003; Egawa et al., 2001; Flohr and Schultz, 2009; Goodman and Rose, 1990; Larsen, 2015; Lewis, 2017; Lynnerup et al., 2000; Primeau et al., 2018; Roberts and Manchester, 2005; Steckel and Rose, 2002).

Harris lines generally develop in periods of accelerated growth during infancy and adolescence (Alfonso et al., 2005; Gindhart, 1969). Using Harris Lines as a skeletal marker has limitations due to diminishment with age due to remodeling as well as a lack of scoring standards (Primeau et al., 2016; Scott and Hoppa, 2015). Harris lines as well as LEH have numerous causes such as nutritional stress without pathogenic involvement (Larsen, 2015; Roberts and Manchester, 2005), whereas IMED has a pathogenic origin (Casselbrant and Mandel, 2003; Homøe, 2001). Infectious middle ear disease has been shown in clinical data to predominantly occur during early childhood followed by a predisposition for further episodes in later years (Chole and Sudhoff, 2010; Teele et al., 1989; Todberg et al., 2014; Vergison et al., 2010). The aim of this study was to evaluate these three skeletal markers for temporal trends co-occurring with environmental changes thereby gaining insight into temporal variability in childhood health throughout the Danish medieval period.

Section snippets

Material

The skeletal sample used in this study was from two cemeteries in northern Jylland, the mainland of Denmark; an urban sample from the town of Randers, and a rural sample from the nearby village of Tjærby (Fig. 1). The skeletal material from these two cemetaries are combined for this study as results showed no statistical significant difference in disease markers between the two samples (see results, Table 3).

Both cemeteries were in use essentially from the beginning to the end of the Danish

Results

Individuals with uncertain sex assignment (“possible male”, “possible female” or “indeterminate”) were not included for analyses by sex. Analyze of sex difference between the two cemetery samples revealed no statistically significant difference for any of the three skeletal markers (Table 2) or for the three skeletal markers within time periods (Table 3), therefore the data (sex and population sample) was pooled for further analysis.

Table 4 shows the presence or absence data of HL based on age

Discussion

The aim of this study was to use three skeletal markers of stress to evaluate evidence of compromised health during the known temporal climatic changes throughout the Danish medieval period. These markers develop during sub-adult years but the reactive changes are still evident in the adult skeleton. This time period of the LIA in the history of Denmark is generally portrayed to be one of unrest, with fluctuating intervals of prosperity and crisis resulting in socioeconomic changes such as

Conclusion

This bioarchaeological study has contributed to the knowledge of health during the medieval period in Denmark in relation to the known mortuary patterns. The chronological burial custom of arm placement in a rather consistent manner has allowed temporal control throughout most of the medieval period in Denmark. The catalytic, if not causative, role of abrupt climate change to significant agricultural shortfall may be manifested on the adult human remains from Randers and Tjærby, as a testament

Funding

This work was supported by the Velux Foundation, grant number: VELUX30089.

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