“An Injurious and Utterly Unfit Environment”: A Case Study Comparing Dental Evidence of Childhood Stress in Nineteenth Century Working‐Class Peoples From British and Colonial New Zealand Contexts

ABSTRACT

Objectives

During the nineteenth century, the health and living conditions of many working‐class European peoples declined in association with growing industrialization and urbanization. Emigration to British colonies grew as people sought to escape such hardships. This research presents the first direct comparison of dental markers of stress in a case study of migrants to a British colony (Otago, New Zealand) alongside a contemporaneous assemblage representing an origin population (London, United Kingdom).

Materials and Methods

Dental markers of childhood stress, accentuated lines, were observed in thin‐sections of archeological teeth from adults (n = 9) and children (n = 16) interred in London, United Kingdom (UK), and adult European migrants interred in Otago, New Zealand (NZ) (n = 24) using standard histological techniques.

Results

All individuals interred in London, and 92% (22/24) of those in New Zealand exhibited evidence of accentuated line formation within the first 2.5 years of life. There was no difference in median accentuated line occurrence between adults and children interred in the UK. However, NZ adults had a lower median occurrence of accentuated lines over the first 2.5 years since birth (5 ALs/individual) than UK adults (13 ALs/individual). Accentuated lines most frequently occurred in infancy for all three groups examined. However, temporal trends in accentuated line occurrence differed between groups in association with age.

Discussion

These results highlight the impact of childhood stresses on working‐class people growing up during the nineteenth century, underlining potential differences in the childhood experiences of hardship in individuals that remained in Britain and those that departed for foreign soils.

1. Introduction

This study describes dental markers of early childhood physiological stress in two archaeological skeletal assemblages through the histological analysis of enamel formation disruption. Exposure to internal or external stressors may produce a physiological stress response that has the potential to affect growing bodies (Cameron and Bogin 2012; Selye 1976; Temple and Goodman 2014). The biological impacts of physiological stress are particularly notable in infants and young children due to their immature immune systems, the demands of growth, and the high level of care and investment they require (Cameron and Bogin 2012; Selye 1976; Temple 2019). As such, bioarchaeological evidence related to childhood stress in the past has the potential to give valuable insight into the stress experiences of the wider population during periods of social, economic, or nutritional transition (e.g., Boldsen 2007; Gamble et al. 2017; Garland et al. 2018; Goodman and Armelagos 1988; Kavale‐Henderson et al. 2024; McCool et al. 2023; Watts 2015).

The British Industrial Revolution and associated colonial expansions of European powers is one such time of rapid social change. Although both childhood stress markers and the biological effects of colonial diaspora are increasingly being scrutinized in the bioarcheological literature (Adams et al. 2023; Buckley et al. 2020; Gurr, Brook, et al. 2022; Gurr, Kumaratilake, et al. 2022; Moes et al. 2022; O'Donnabhain and Lozada 2018; Peckham 2015), to date there have not been studies comparing microscopic stress markers in dental enamel between contemporaneous emigrant and non‐emigrant skeletal assemblages. Yet, a consistent historical narrative has become accepted, asserting that in British colonial contexts emigrants were driven by increasing adversity in their home country and lured by the promise of better future prospects overseas (Constantine 2003; Phillips and Hearn 2008; Woods 1996). These key “push”‐ and “pull”‐factors were instrumental for shaping the global nineteenth century (Ballantyne 2012), however, their embodiment in migrants compared to non‐migrants is under‐researched. Commonly used and widely available analytical techniques, such as examination of biomarkers of physiological stress in teeth, can further shed light into early life experiences and potential drivers for migration.

Tooth enamel formation begins in utero and continues until early adolescence, holding a permanent record of early growth as enamel is not remodeled after initial formation (Hillson 2005). Teeth are typically the best‐preserved part of the skeleton in archaeological contexts due to their high mineral content (Hillson 2005; Miszkiewicz and Mahoney 2017), preserving a window into early life. Commonly, stress biomarkers are interpreted as indicators of hardship: an experience of higher than usual exposure to external stressors (Temple and Goodman 2014). The impacts of hardship may vary throughout the life course, and the preservation of biomarkers of stress during early life reflects the unique stressors and environmental interactions to which infants and children are subjected. The first 1000 days from conception have been identified as a notably vulnerable and plastic period (Barker 2007), outlined in the Developmental Origins of Health and Disease (DOHaD) paradigm (Gluckman et al. 2016). Thus, the trajectory of normal growth and development of an individual is not set at birth, but will transform as they interact with their wider biosocial landscape (Agarwal 2016). Notably, this early life adaptive plasticity can result in trade‐offs in later life, impacting patterns of morbidity and mortality over the life course (McPherson 2021).

This study applies this theoretical framework to consider dental histological evidence of childhood stress in two skeletal assemblages: adults and children that lived and died in London, United Kingdom (UK) (c. 1800–1850 ad), and early European settlers of Otago, New Zealand (c. 1820‐1880 ad). This work presents a novel bioarcheological comparison of nineteenth century migrants to a distant British Colony against a contemporaneous group that were born and continued to live in their shared homeland. By examining evidence for physiological stress in the dentition, this study addressed two main hypotheses:

1. The occurrence of childhood stress markers in the teeth of this group of individuals who died in Britain will be lower in comparison to colonial adult migrants to New Zealand.

2. Temporal patterns of evidence for growth disruption will vary in relation to key developmental and biological stages, and that this will differ between children and adults that lived and died in England, and a contemporaneous group of individuals that emigrated to New Zealand as adults.

1.1. Historical Context

The British Industrial Revolution began in the late eighteenth century AD, and by the early nineteenth century the impact of industrialization was apparent on the living and working conditions of millions of British residents (Buer 1926; Wrigley 2018). The first half of the nineteenth century saw rapid urban expansion within Great Britain (GB) in association with a shift in work availability and type, as well as resource distribution and access (Davenport 2021). Cities such as London, Manchester, and Birmingham became industrial centers, attracting thousands of working‐class people from rural British and Irish backgrounds (Davenport 2021; Pooley and Turnbull 1996). The working‐class was disproportionally affected by changing environments during the Industrial Revolution, and previous studies have demonstrated clear biological impacts of the Industrial Revolution on childhood growth and health (e.g., Boyd 2020; Buckberry and Crane‐Kramer 2022; DeWitte et al. 2016; Gowland 2018; Reedy 2020; Yaussy 2024). These impacts were often compounded, as the lower socioeconomic classes were more likely to be exposed to or experience repeated infections and poor nutrition, with less access to medical care (Buckberry and Crane‐Kramer 2022; Gowland et al. 2023; Ives and Humphrey 2018; Luckin 1984).

As global migration opportunities arose during the nineteenth century through British Imperial expansion, people also chose to depart their homelands to improve their lives and those of future generations (Ballantyne 2012; Constantine 2003). Aotearoa New Zealand (NZ), hereafter referred to as New Zealand, was established as a formal British colony in 1840, and the European population grew rapidly through assisted migration schemes (Ballantyne 2012; Phillips and Hearn 2008). New Zealand was marketed during the nineteenth century as a land of opportunity for the lower classes in Britain, offering opportunities for increased social mobility, health improvements, and security from hardship that could not be found in the UK (Ballantyne 2012; Newman 1882; Phillips and Hearn 2008; Ward 1840). Shipping companies offered subsidized migration to New Zealand for working‐class people of “good health and character” (Figure 1) (Phillips and Hearn 2008), and many departed with a hope for better and healthier lives than could be expected back “home” (Ballantyne 2012; Constantine 2003; Phillips and Hearn 2008; Soper 1948). In the 1850s and 1860s, self‐assisted migration out of Europe also grew as a series of gold‐rushes occurred across the globe (Carpenter and Fraser 2016; Holliday and Swain 1981). These attracted waves of prospective miners, predominantly young working‐class men, hoping to strike their fortunes in regions such as Australia, North America, and New Zealand (Carpenter and Fraser 2016; Hearn 2016; McConville et al. 2016). Much of the Otago goldfields population was itinerant, pulled by the prospect of working the goldfields for quick financial gains but not intending to settle permanently in New Zealand (Carpenter and Fraser 2016).

FIGURE 1.

Advertisements for New Zealand offering free or subsidized migration, targeted at laborers, mechanics and domestic servants of “good character”. Left image obtained from the Hocken Collections, University of Otago (REF Eph‐0023‐JV‐D‐07). Right image obtained from the Auckland Council Libraries—Tāmaki Pātaka Kōrero o Tāmaki Makaurau, Sir George Grey Special Collections (REF 7‐A12523).

1.2. Enamel Formation Disruption as an Indicator of Physiological Stress

Enamel formation occurs rhythmically and the matrix is deposited sequentially by ameloblasts. Ameloblasts exhibit regular variation in the rate at which they secrete enamel, resulting in histologically visible incremental structures within the tooth (Figure 2a) (Hillson 2014). Long‐period incremental markers, known as Retzius lines or striae of Retzius, represent 6–11 days of enamel formation and are visible at and just below the outer lateral enamel surface (Figure 2a) (Gysi 1931; Mahoney 2008; McFarlane et al. 2021; Miszkiewicz and Mahoney 2017; Retzius 1837; Risnes 1986). Short‐period incremental markers, known as prism cross‐striations, appear as alternating light/dark bands and represent approximately 24 h of enamel formation (Figure 2b) (Antoine et al. 2009; Dean 1998; Lemmers et al. 2021). When prism cross‐striations are visible they can be directly counted, following the ameloblast path from the dentin‐enamel junction (DEJ) to the outer enamel surface (Figure 2b), to estimate enamel formation times (Antoine et al. 1999; Antoine et al. 2009; Aris 2022; Dean and Scandrett 1996). Where visibility of prism cross‐striations is poor, regional measurements can be taken to estimate local enamel daily secretion rates (DSRs) (Kavale‐Henderson et al. 2024; Mahoney 2008; McFarlane et al. 2021), the method for which is described in detail in Section 2.3.

FIGURE 2.

Dental enamel section of a permanent canine, illustrating regular incremental structures. (A) Black arrows indicate the position of Retzius lines. Double headed white arrows illustrate the regular spacing of prism cross‐striations between Retzius lines, denoting the Retzius periodicity. (B) Inset of A, arrows indicate prism cross‐striations, formed of one light and dark unit.

Systemic stress during enamel deposition can impact ameloblast function, resulting in macroscopic surface defects, as well as microscopic changes to the internal enamel structure (Boldsen 2007; Goodman and Rose 1990; Witzel et al. 2008). Enamel formation disruption has many possible potential etiologies, including infectious disease, malnutrition, trauma, weaning and psychosocial stress (Blakey et al. 1994; Davis et al. 2020; Floud et al. 1990; Goodman and Armelagos 1988; Koutlias 2019; Roberts and Manchester 2005; Steckel 2008), and is a widely used and well‐established indicator of non‐specific physiological stress during early life (Armelagos et al. 2009; Blakey et al. 1994; Boldsen 2007; Erkman et al. 2022; Goodman and Rose 1990). Analyses of enamel defects associated with stress are broadly used in bioarcheological research, both in understanding patterns of morbidity and mortality in relation to individual frailty (e.g., Lawrence et al. 2021; O'Donnell and Moes 2021), and to investigate the stresses of infancy and childhood (e.g., DeWitte et al. 2025; Garland et al. 2018; Moes et al. 2022).

Macroscopic surface markers of enamel formation disruption (enamel hypoplasia) correspond to changes in internal dental microstructure that are visible in histological thin sections, known as accentuated lines (ALs), or Wilson Bands (Aris 2020; Austin et al. 2023; FitzGerald and Saunders 2005; Rose et al. 1978; Rose et al. 1984; Wilson and Shroff 1970). Accentuated lines are distinguished from Retzius lines by their irregular width, darker appearance, and visibility over more (> 50%) of the enamel width (FitzGerald and Saunders 2005; Lorentz et al. 2021; Mahoney et al. 2017; Witzel et al. 2008). A prominent accentuated line that forms shortly after birth, known as the neonatal line, demarcates prenatal and postnatal enamel in the deciduous dentition and most permanent first molars (Hillson 2005). As the neonatal line gives a baseline of when an individual was born, it is possible to estimate the age of accentuated line formation after birth by either directly counting prism cross‐striations or by using regional DSRs (Kavale‐Henderson et al. 2024). For permanent teeth forming after birth, it is necessary to estimate the approximate age at which enamel formation began from available dental standards (Nelson 2015; Reid and Dean 2006).

Although histological analysis of the dentition is destructive, it provides more accurate estimates of the age at which individuals experienced enamel formation disruption than macroscopic analyses. These techniques also complement other destructive testing methods, such as those used for isotopic, aDNA, and peptide analyses, and a collaborative sampling approach can minimize destructive sampling while maximizing the information obtained (e.g., Esposito et al. 2024). This study incorporates histological analysis of residual tooth sections from prior incremental isotope analysis to investigate evidence of physiological stress in anonymous individuals from a working‐class British setting (O'Donoghue 2023). By comparing these results to previous observations of evidence for childhood stress in a colonial New Zealand settler population (Kavale‐Henderson et al. 2026), this study contributes to a critical examination of biosocial landscapes for the “everyday person” in a global context.

1.3. Contextualizing Physiological Stress Markers in Theoretical Frameworks

Stress indicators, such as those analyzed in this study, represent the physical manifestation of a series of complex adaptive changes to the body's physiological state as a trade‐off must be made between the distribution of energy and resources (Worthman and Kuzara 2005). This trade‐off is key to the tenets of DOHaD, and, as such, is known to inform future responses of the body when hardships are experienced (Barker 2007; Worthman and Kuzara 2005). Although DOHaD accounts for these impacts on an individual at the biological level, early life hardship may also influence adolescent and adult sociocultural behaviors (Birn et al. 2017; Xu 2021). Thus, it is important to consider not only trade‐off events that may have occurred throughout the life course, but also the age of the individual (Elder et al. 2003). Consideration of life course theory can thus further guide the design and interpretation of studies of past populations, with particular emphasis on the interrelatedness of individual life histories, and communities as a whole (Agarwal 2016).

While historical literature suggests that British emigrants benefited from their move across the globe, little focus has been given to their pre‐migratory experiences in their origin countries. By comparing New Zealand migrants to individuals that remained at “home,” this study explores whether there were differences in embodied stress experiences between our two populations. The established historic narrative suggests nineteenth century British colonial migrants were motivated to leave their natal land through increasing adversity and the lure of overseas British colonies. As such, it is expected that the occurrence of accentuated lines, a marker of early life stress experiences, will be differently exhibited over the first years of life in migrants compared to non‐migrants.

2. Materials and Methods

2.1. Archeological Sites and Samples

This study describes observations of accentuated lines in the archeological remains of nine adults and 16 children from the New Bunhill Fields cemetery in London, UK, and 24 adults from three cemeteries in South/Central Otago, New Zealand. All individuals were interred during the nineteenth century (Table 1, Figure 3a,b). Site and sample summaries are provided in Table 1. The inclusion of children who were born in and died in New Zealand was not feasible for this study due to the limited nature of dental preservation in this age group. As the New Bunhill Fields setting was conducive to good preservation, it enabled an additional comparison of the frequency and timing of accentuated lines between survivors and non‐survivors at this site.

TABLE 1.

Summary of archaeological samples included in this study.

Site	Site abbreviation	Archaeological site code	Cemetery dates of use (all dates AD)	Number of individuals analyzed
New Bunhill Fields, Southwark, UK	NBF	DVL05	1821–1853	25 (9 adults, 16 non‐adults)
St John's Anglican Burial Ground, Milton, Tokomairiro Plain, NZ	SJM	H45/156	c. 1860–1890	8 adults
Ardrossan St Cemetery, Lawrence (Tuapeka), NZ	AS	H44/1135	c. 1861–1864	13 adults
Drybread Cemetery, Manuherikia Valley, NZ	DB	G41/630	c. 1860s—currently in use	3 adults

FIGURE 3.

(A) Map of England, indicating the location of the New Bunhill Fields Burial Ground, London. (B) Map of New Zealand, indicating the location of the three cemeteries examined in this study relative to major centers.

2.1.1. New Bunhill Fields, Southwark, London, England

The New Bunhill Fields cemetery in the London suburb of Southwark was used between 1821 and 1853, and the portion excavated in 2008 has no surviving associated burial registers (Miles and Connell 2012). Historical records indicate those interred were predominantly part of the local non‐conformist population, a term that captures any Protestant outside of the Church of England (Anglican) faith (Miles and Connell 2012). The cemetery was affordable to all levels of London society; however, the individuals included in this study were recovered from a section thought to predominantly contain individuals of working‐class backgrounds (Miles and Connell 2012). Local industry in Southwark at the time centered around manufacturing, such as metalwork, brewing, tanning, textile, and clothing production (Yaussy 2024). By 1851, over 40% of women and 50% of men were employed in manufacturing roles, with most of the remaining population engaged in services such as food and drink supply (Field 2018). Although the skeletal and dental preservation from this site was generally good, dental pathologies such as carious lesions were common (Miles and Connell 2012), limiting the number of teeth that could be sectioned. Samples for this study were permanent first molars available from a previous isotopic study (O'Donoghue 2023). Teeth with excessive wear or pathology obscuring one or both cusps were excluded. Museum of London Archaeology guidelines limited sampling to individuals with an antimere present and to only 50% of any age‐cohort (O'Donoghue 2023, 94). Permission for further destructive analyses of the residual half‐sectioned teeth was obtained from the Museum of London (MOLA) and the Biological Anthropology Research Centre (BARC), University of Bradford, for the present histological study.

2.1.2. New Zealand Cemeteries

Summaries of the excavations, archeological contexts and cemetery overviews from St John's Anglican Burial Ground, Milton (herein referred to as St John's Milton), Ardrossan Street cemetery and Drybread cemetery have been previously published in detail (Kavale‐Henderson et al. 2024, 2026; Petchey and Buckley 2026; Petchey et al. 2023). Initial excavation was preceded by extensive formal community consultation, and appropriate disinterment licenses and archaeological authorities were obtained (Petchey and Buckley 2022; Petchey et al. 2018, 2023). The analysis of historical New Zealand dental samples was approved by the University of Otago Human Ethics Committee (25/1244). All human remains analyzed from the New Zealand cemeteries have been reburied with descendant community involvement and appropriate cultural consideration. Skeletal preservation at all sites was variable, and dental wear and pathological conditions also limited sample selection. Due to this, more than one tooth was sampled per individual where possible, to create overlapping enamel formation chronologies. Preservation of non‐adults from these cemeteries was exceptionally poor, with most infants and children represented by heavily stained deciduous tooth enamel “caps” (Kavale‐Henderson et al. 2024). Due to limited enamel visibility due to taphonomy, and the very small (< 3) number of permanent first molars available for histological sampling from these non‐adults, only New Zealand migrant adults are included in this comparison.

The town of Milton was established in the 1850s in association with European agricultural development of the Tokomairiro plain, before becoming a vital service town on the route to the Otago goldfields (Sumpter and Lewis 1949). The St John's Milton burial ground was in use by residents of Milton and nearby mining settlements such as Canada Reef (Petchey and Buckley 2022). A township at Lawrence (formerly Tuapeka) began as an unplanned mining settlement in 1861, when thousands of men flocked to nearby goldfields, and the individuals interred in the Ardrossan Street cemetery represent some of the earliest goldminers in the area (Petchey et al. 2018). The settlement of Drybread was associated with both local goldmining activity and sheep runholding (farming) throughout the mid‐late nineteenth century (Petchey et al. 2023), and whilst the township disappeared, the cemetery remains in active use today. All adult New Zealand migrants included in this study are likely to have been of British or Western European birth, and all adults from New Zealand were first generation migrants as demonstrated through previously published isotopic and historical evidence (King et al. 2020, 2021, 2023; Petchey and Buckley 2022). These individuals died and were interred in Otago, New Zealand during the second half of the nineteenth century (c. 1857–1903) (Petchey and Buckley 2022, 2026; Petchey et al. 2023).

2.2. Dental Samples

Tooth samples were analyzed from 25 individuals interred in New Bunhill Fields cemetery and compared with published chronologies of accentuated lines in 37 teeth from 24 individuals from St John's Milton, Ardrossan Street cemetery, and Drybread cemetery (Kavale‐Henderson et al. 2026) (Table S2). All individuals from New Bunhill Fields are represented by mandibular permanent first molars. First molars were also sampled for 18 of the 24 individuals interred in the three New Zealand cemeteries. In five of these 18 individuals, teeth other than a first molar were also sampled (see Table S2 for full details). In cases where multiple teeth were sampled, accentuated lines were matched across teeth to compose a single timeline of enamel formation, including prenatal enamel, and prevent double counting of accentuated lines (Lemmers et al. 2021). Six individuals in the New Zealand sample are represented solely by tooth types that begin enamel formation after birth. For these sampled teeth, an average age of enamel secretion initiation was estimated from dental enamel formation standards (Schour and Massler 1940). In these samples, measurements to estimate crown formation chronologies and age of accentuated line occurrence started from the innermost cuspal enamel adjacent to the dentin horn apex. The average age of enamel secretion was then added to these measurements to better estimate the chronological age of the individual at the time when each specific tooth was forming.

Only the first 2.5 years of enamel formation time samples were considered in the New Zealand samples. This allowed for better comparison with the first molars from New Bunhill Fields, in which enamel formation is typically completed between 2.5 and 3 years of age (AlQahtani et al. 2014), and captured a notable developmentally plastic window. Demographic summaries of sampled individuals are provided in Tables S1 and S2. Non‐adults are defined as individuals below approximately 18 years of age at the time of death.

2.3. Slide Preparation and Analysis

Dental samples were prepared for histological analyses following established methods (Aris 2020; Miszkiewicz and Mahoney 2017). The materials and methods used to produce thin sections of the teeth from St John's, Milton, Ardrossan Street, and Drybread cemeteries have been previously published in detail (Kavale‐Henderson et al. 2024). Dental samples from New Bunhill Fields were selected from previously sampled molars in which a bucco‐lingual section through the two most distal or mesial cusps could be achieved through a fully formed enamel crown. Teeth were embedded in epoxy resin (Buehler Epothin 2) under vacuum in a Buehler SimpliVac vacuum mounting system (Bancroft and Gamble 2008). Embedded tooth residuals were sectioned on a Leica SP1600 Microtome, as close to the dentin horn apex as possible. A second cut was made 1 mm from the first, and this thin section was mounted to a glass slide using Logitech 0CON‐186 UV resin and cured for 30 s under a UV lamp. Sections were reduced to a final thickness of ~100–120 μm by wet sanding with 400 grit/P600 and 600 grit/P1200 silicon carbide paper on a Buehler Phoenix Beta grinder‐polisher. An Olympus CX41 microscope was used to check sample thickness and to confirm clarity of enamel microstructure. Samples were then wet‐polished with 6 and 1 μm Buehler MetaDi Supreme Polycrystalline Diamond Suspension polishing compound and dehydrated with 95% and 100% ethanol (Bancroft and Gamble 2008).

Whole‐tooth images of slides from New Bunhill Fields were captured using transmitted light on a Keyence VHX‐7100 digital microscope equipped with VXH‐E100 lens at 100× total magnification. Regions of interest (ROIs) were identified and captured at 200× total magnification on a Leica DMLB 12MP USB 2.0 microscope and Mosaic v2.4 software for brightfield analysis. Images were viewed in ImageJ/FIJI software, and accentuated lines (ALs) were identified and traced using the line tracing tool (Kavale‐Henderson et al. 2024). Accentuated lines were distinguished from regular incremental lines such as Retzius lines due to their darker and thicker appearance and visibility across at least 75% of the distance between the DEJ and the outer enamel surface (FitzGerald and Saunders 2005; Kierdorf et al. 2021; Rose et al. 1984; Schwartz et al. 2006; Witzel et al. 2008). Where visible, the neonatal line was identified and traced.

Recent histological investigations of enamel formation disruption raised concerns about potentially high levels of subjectivity when identifying and recording accentuated lines (Lemmers et al. 2025). To mitigate this potential bias, in this study, each dental thin section was imaged under regular scattered light and polarized light to create virtual slides. Each of these virtual slides was observed non‐consecutively (i.e., all scattered light images were analyzed, followed by all polarized light images), and potential accentuated lines were identified on both sides of the tooth section. These potential accentuated lines were compared between the left and right sides of the tooth section images, and between the scattered light and polarized light virtual slides. To minimize false‐positive observations, accentuated lines that appeared to match were confirmed if their estimated age‐at‐occurrence aligned, or if cross‐striation counts between adjacent accentuated lines were consistent.

Regional DSRs were calculated for the inner, middle, and outer third of the cuspal and lateral enamel, as an average of 20 observations of five prism cross‐striations following the ameloblast path from the DEJ toward the enamel surface (Kavale‐Henderson et al. 2024). All DSRs fell within the established DSR ranges for the sampled tooth types (Tables S3 and S4) (Antoine et al. 2009; Aris 2022; Aris et al. 2020; Dean et al. 2020). Age‐at‐AL occurrence was estimated relative to either the neonatal line or from the cuspal enamel closest to the dentin horn apex. Regional enamel DSRs were used to convert a straight‐line measurement following the enamel prism path in μm to calendar days. Where possible, direct counts of prism cross‐striations and/or Retzius lines were used to estimate the number of days between the neonatal line and an accentuated line or between subsequent accentuated lines. Daily enamel secretion rates were also used to estimate the age of crown completion.

Due to limitations in enamel visibility (e.g., loss of cervical enamel or obfuscation due to taphonomic staining), only enamel that was forming between birth and approximately 30 months of age was compared between the three groups. Occurrence and patterns of accentuated line formation were further considered regarding key biological and developmental changes that occur as an infant transitions from being a newborn and fully reliant on parental investment to a toddler that can begin to independently interact with the environment (Cameron and Bogin 2012). This is important as the intrinsic and extrinsic factors that may impact both the nature of physiological stress at this time and the buffering of stressors in infants and young children differ through early life (Halcrow and Tayles 2008; Scheuer and Black 2000). Additionally, this allows critical examination of the findings of this study under DOHaD, as the first couple of years of life are a notably sensitive period of development (Gluckman et al. 2016; Worthman and Kuzara 2005). This was achieved by grouping the data into 6‐month long brackets to better consider how patterns of stress markers may vary through a portion of the life course (Table 2) (Cameron and Bogin 2012; Gowland and Caldwell 2022; Scheffler and Hermanussen 2018). All statistical comparisons between groups were undertaken using RStudio (v4.5.1) (RStudio Team 2020).

TABLE 2.

Summary of time blocks adopted in this paper and their corresponding biological and societal landmarks.

Age bracket	Life stage	Key biological and societal markers and changes
Birth to under 6 months	Newborn to early infancy	Extremely vulnerable and reliant on parental investment, immature immune system, weaning occasionally initiated
6 to under 12 months	Early to mid‐infancy	Growing mobility (can sit up, grasp items), first teeth eruption, introduction of solid foods and frequent initiation of weaning by working‐class mothers
12 to under 18 months	Mid‐infancy	Greater mobility and independence from parent, beginning to self‐feed
18 to under 24 months	Mid to late infancy	Cessation of weaning, deciduous dental eruption ending, walking and talking begin, can self‐feed
24 to under 30 months	Early childhood	Less reliant on direct parental investment, End of weaning, considered by nineteenth century Western society as “children” rather than “infants”

Note: Life stages defined regarding biological growth and development over the first 3 years of life (Gross 2024). Societal markers derived from historical contextual literature regarding infant and child rearing in working‐class contexts of nineteenth century Britain (Bull 1842; Fildes 1998; Wickes 1953; Wrigley et al. 1997).

3. Results

3.1. Occurrence of Accentuated Lines in Individuals From New Bunhill Fields

Accentuated lines were observed in all sampled teeth from New Bunhill Fields. Overall, non‐adults (n = 16) exhibited between two and 19 accentuated lines per tooth (Figure 4, Table S5), with a median occurrence of 10.5 accentuated lines per individual. The adults (n = 9) exhibited between six and 20 accentuated lines per tooth (Figure 5, Table S6), with a median occurrence of 13 ALs per individual. The non‐adult NBF1043 was the only person in the New Bunhill Fields sample to exhibit fewer than six accentuated lines in the sampled tooth, while other non‐adults displayed a minimum of eight accentuated lines (Table S6).

FIGURE 4.

Chronology of accentuated line formation in non‐adults from New Bunhill Fields (i.e., estimated to have died prior to reaching c. 18 years). Horizontal gray bars represent the approximate age at which the preserved enamel was forming based on dental histological observation of enamel incremental markers. Vertical red lines indicate the approximate age of accentuated line formation (representing an episode of physiological stress experienced).

FIGURE 5.

Chronology of accentuated line formation in adult individuals from New Bunhill Fields. Horizontal gray bars represent the approximate age at which the preserved enamel was forming based on dental histological observation of enamel incremental markers. Vertical red lines indicate the approximate age of accentuated line formation (representing an episode of physiological stress experienced).

The three adult females sampled displayed a narrower range of accentuated lines (7–9 per tooth) when compared to the six adult males (6–20 ALs per tooth) (Table S6). No adult exhibited formation of accentuated lines beyond the age of approximately 24 months (Figure 5, Table S5). However, five of the fifteen non‐adults for which enamel was forming during this time exhibited accentuated lines, with the latest forming accentuated line estimated to have occurred at around 34 months of age (Figure 4, Table S5). When considering the first two years of enamel formation (excluding individual NBF1411 for whom enamel formation was visible until approximately 1.5 years of age), no significant difference was observed between median accentuated line occurrence in adults (n = 9) and non‐adults (n = 15) from New Bunhill Fields (Wilcoxon rank‐sum test with continuity correction, p = 0.74).

3.2. Temporal Patterns of Accentuated Line Occurrence

This section considers the occurrence of accentuated lines grouped by chronological age in months since birth in the two groups of individuals from New Bunhill Fields (UK non‐adults and UK adults), alongside adult migrants to New Zealand (NZ adults) (Figure S1, Table S7). Figure six depicts the average number of accentuated lines observed in individuals within each group. The same period of their life (e.g., the first six months after birth) was compared, divided into six‐month time blocks that span birth to 2.5 years of age. The data upon which this is based is presented in Table S8.

Overall, the enamel of UK adults exhibited a higher frequency of accentuated lines compared to NZ adults over the first 2.5 years of life. When comparing the median occurrence of accentuated lines in UK adults (n = 9) compared to NZ adults (n = 15), for whom the entire period of birth to 2.5 years of age was visible in the enamel, UK adults had a significantly higher count of accentuated lines (13 ALs/individual) compared to NZ adults (5 ALs/individual) (Wilcoxon rank‐sum test with continuity correction, p = 0.01).

The two assemblages also displayed dissimilar chronological patterns of accentuated line formation. For all groups in this study, the highest occurrence of accentuated lines per individual was observed in the first year of life (UK non‐adults average 6.9 ALs/individual, UK adults average 7.9 ALs/individual, NZ adults average 4 ALs/individual). Both the UK non‐adults and UK adults showed evidence of a higher average number of ALs/individual than the NZ adults in each time block, except for the 24‐to‐30‐month period (Figure 6). The average accentuated line occurrence for UK non‐adults and UK adults was similar in the 6‐to‐12 month (UK non‐adults average 4 ALs/individual, UK adults average 3.7 ALs/individual) and 12‐to‐18‐month time blocks (UK non‐adults average 2.4 ALs/individual, UK adults average 2.2 ALs/individual). However, in the first six months of life, the average number of ALs/individual in UK non‐adults (2.9 ALs/individual) was more similar to that of NZ adults (2 ALs/individual) than UK adults (4.2 ALs/individual).

FIGURE 6.

Average number of accentuated lines observed in the demographic group (shown in legend) and categorized into five six‐month age blocks (horizontal axis). Individuals with teeth that could not be scored for a specific age band were excluded from the calculation. These age bands represent six‐month developmental periods from birth to 2.5 years of age. All individuals were likely born in Europe between c. 1810–1850 ad and have been grouped into those that did not survive to adulthood (UK non‐adults), those that died in Great Britain as adults (UK adults), and those that emigrated (presumably from Western Europe) to New Zealand prior to death but after childhood (NZ adults).

The pattern of accentuated line occurrence over time was not consistent between the three groups. The average accentuated line occurrence for UK non‐adults was highest between six and 12 months of age (4 ALs/individual), followed by a reduction in each subsequent time block. For UK adults, average accentuated line occurrence was highest in the earliest months of life, between birth and six months of age (4.2 ALs/individual), with a subsequent decline in accentuated line occurrence with aging. Similarly, the highest occurrence of average accentuated line occurrence in NZ adults was observed in the first year of life (0–6 m and > 6–12 months both exhibit 2 ALs/individual), followed by a decline in the second year (> 12–18 months 1.3 ALs/individual, > 18–24 months 0.7 ALs/individual). However, in NZ adults the average accentuated line occurrence increased in the last time block, between 24 and 30 months of age (0.9 ALs/individual).

4. Discussion

4.1. Dental Stress Markers in Individuals From New Bunhill Fields, London

Evidence of enamel formation disruption was observed in all teeth examined from New Bunhill Fields, primarily estimated to have occurred during infancy (Table 2, Figures 4 and 5). The highest count of accentuated lines per person was similar in both adults (maximum 20 ALs) and non‐adults (maximum 19 ALs), and the lowest count was six accentuated lines in adults and as low as two accentuated lines in one non‐adult (NBF1043) individual. Interestingly, in the New Bunhill Fields sample, there seemed to be no differences in the overall occurrence and temporal pattern of accentuated lines between those that survived to adulthood and those that did not. This suggests that external stress factors may have been endemic to the broader population at the time, rather than representing individual fluctuations in frailty. This finding is also consistent with DOHaD, notably that the plasticity and vulnerability of infancy renders them susceptible to unique stressors and environmental interactions of early childhood (Gamble and Bentley 2022).

This evidence for preserved experiences of childhood physiological stress is consistent with historical accounts of hardships among the working‐classes of England during the Industrial Revolution. The early British epidemiologist William Farr described those living in UK cities as “immersed in an atmosphere that weakens their powers, troubles their functions, and shortens their lives” (Farr 2001, 38). Contemporary writer and political theorist Friedrich Engels also described life in the poorer areas of British cities as “injurious to health” (Engels 2001, 68), with many of the laboring class subsisting on inadequate diets for adults and “utterly unfit for young children” (Engels 2001, 71). Despite the often‐negative historical view of life in the lower classes in the nineteenth century, these survived episodes of stress also highlight the resilience of children growing up during the Industrial Revolution (DeWitte et al. 2025).

4.2. Comparing Evidence for Childhood Hardship Between UK Residents and Early NZ Settlers

The results presented here indicate hardship likely affected during the early lives of both this group of adults that died in the UK, and those that departed for foreign lands who eventually died and were buried in New Zealand. Contrary to the expectations of the first hypothesis of this study, the overall occurrence of accentuated lines was lower in the NZ adults compared to both adults and non‐adults from the UK. All UK adults and 92% of NZ adults exhibited clear evidence of accentuated line formation. Two NZ adults (SJM29 and A9) did not exhibit observable accentuated lines, and SJM29 also did not exhibit macroscopic markers of enamel formation disruption in his dentition (Snoddy et al. 2021). It has been suggested that SJM29 may have been more privileged in life than his peers in the cemetery, as he had the finest coffin furniture found in St John's Milton (Petchey and Buckley 2022). However, it cannot be inferred that his life was without hardships, as his skeleton did exhibit extensive deformities, likely due to a skeletal growth disorder (Snoddy et al. 2021). As there is little contextual information available regarding A9, other than his likely role as a goldminer in Otago, his childhood status cannot be inferred. It was also observed that the median number of accentuated lines per individual between birth and 2.5 years of age was lower in the NZ adults than the UK adults.

Alongside observations of widespread accentuated lines in the dentition, when comparing the first 2.5 years of enamel formation the highest occurrence of accentuated lines per individual was observed in the first 12 months of life (newborn to early‐mid infancy) in all three groups (UK non‐adults, UK adults and NZ adults) (Table 2, Figure 6). In UK adults, accentuated line prevalence declined with chronological age, whereas the UK non‐adults exhibited a peak in accentuated line occurrence between six and 12 months of age (Figure 6). In contrast, NZ adults did not show an apparent difference in the number of growth disruption events experienced over the first six months of life when compared to the following period (6 to 12 months of age) (Figure 6).

4.3. Temporal Patterns in Stress Indicators in Relation to Infant and Child Development

As summarized in Section 2.3, infancy and early childhood are marked by key developmental, social, and biological milestones (Table 2). These differences have important implications for the analysis of evidence for disruptions to growth, such as accentuated line formation, as both intrinsic and extrinsic factors may impact an individual's' response to physiological stress (Goodman and Rose 1990; Kierdorf et al. 2021; Shaffer et al. 2022; Simmer and Hu 2001). Notably, formation of skeletal indicators of physiological stress during development may be influenced by the timing of hardship in relation to developmental plasticity and sensitivity to stressors (Corron et al. 2025). This section describes temporal patterns of accentuated line occurrence in three groups (UK non‐adults, UK adults and NZ adults) over the first 2.5 years of their lives. As outlined in hypothesis two, it was expected that these patterns would be dissimilar between the three groups, and that this could be related to developmental and biological changes during infancy and early childhood.

The slowing of accentuated line formation from early infancy to early childhood in all groups is consistent with biological and societal changes wherein children become less dependent on parental/external investment. Early infancy is one of the most vulnerable periods of life, as the infant is solely reliant on outside help for feeding. Additionally, infants are born with an immature immune system (Arterberry et al. 2023; Gross 2024), increasing susceptibility to infectious disease. Conversely, infants are proffered immune protection through breastfeeding, as maternal antibodies are transferred through breastmilk (Adhikari et al. 2022; Bravi et al. 2016). Premature weaning, alongside the early introduction of outside food sources, may generate further stress to an infant as novel pathogens can be introduced and their nutritional needs may be unmet (Foote and Marriott 2003; Katzenberg et al. 1996; Morgan et al. 2004; Smith et al. 2023). Many nineteenth century working‐class women faced challenging childrearing conditions and weaning infants younger than 6 months was not uncommon as parents were obliged to return to or find work outside the home (Benson 1989; Davenport 2021; Wrigley et al. 1997). It is thus perhaps not surprising that across all three groups (UK non‐adults, UK adults and NZ adults), the highest frequency of accentuated lines per individual was observed in the first 12 months of life.

In the first year of life, the average number of accentuated lines per individual for those that migrated to New Zealand as adults was almost half that of UK non‐adults and UK adults, and this pattern continued up to 24 months of age (Figure 6). Selection criteria for migrants to the colony of New Zealand, whilst no means strictly enforced, included young adults of good health (Newman 1882; Phillips and Hearn 2008; Ward 1840), suggesting that the NZ adults described in this study potentially experienced less ill‐health in early childhood than the UK adults (Gowland 2015).

It is worth noting that, whilst overall the frequency of accentuated lines in the NZ adults was lower in the 24‐to‐30‐month age bracket, NZ adults exhibited a higher average number of accentuated lines per individual compared to UK non‐adults and UK adults (Figure 6). If the absence of accentuated lines in the UK adults beyond two years of age is related to an improvement in their circumstances (Figure 5), it is possible that these individuals may not have felt the same “push” to migrate that those that departed for New Zealand experienced. However, as these individuals reached the end of the first developmentally sensitive life period, this difference in childhood stress experiences may reflect complex interactions of the body as a biological structure, improved biological resilience and sociocultural buffers favoring survival during hardship (Gamble and Bentley 2022; Gretchev et al. 2026; McPherson 2021; Schaefer et al. 2022). This is consistent with the DOHaD paradigm, as these findings reinforce how the trajectory of normal growth and development of an individual may be transformed through interactions with their wider biosocial environment (Agarwal 2016; Gamble and Bentley 2022).

4.4. Early Life Stress in the Context of Global Migration

A key challenge of interpreting this potential embodiment of push‐ and pull‐factors in skeletal assemblages is the limited contextual knowledge regarding the lived circumstances of working‐class people at this time (Beaudreau 2023). Historical studies of colonial New Zealand frequently emphasize that organized European settlers arrived in search of better living conditions and prospects for themselves and their children (Ballantyne 2012; Phillips and Hearn 2008; Soper 1948). However, some of the New Zealand adults in the sample would not have emigrated through organized migration schemes, as many of the people living and working on the Otago goldfields arrived under their own steam (Carpenter and Fraser 2016). Nevertheless, these people may have been screened for health conditions when they initially departed Western Europe (Phillips and Hearn 2008; Woodward and Blakely 2014) and would have needed to be fit and healthy enough to survive and work in the harsh goldfield frontier environment (Mackay 1992).

Ultimately, the perceived benefits of departing the UK may have been colored by working‐class people's experiences of improvement in their circumstances during childhood and early adulthood. The idea that migration may have knock‐on effects ties in with life course theory, specifically the idea that the timing of life events may impact both mobility and future outcomes for individuals (Worthman and Kuzara 2005). Recent research in the modern United States has highlighted life course events as a stimulant to migration, particularly for younger adults (Horowitz and Entwisle 2021). In this modern context, migration may pose a mechanism for individuals that are transitioning to adulthood to re‐attain a level of socioeconomic status they experienced in childhood (Horowitz and Entwisle 2021). In tandem with this motivation to move, modern research has shown early life adversity and hardship are associated with decreased prospects for young adults, in particular opportunities for education and work (Elsenburg et al. 2025; Horowitz and Entwisle 2021; Xu 2021).

By applying this life course approach to this case study, it could therefore be argued that the temporal patterns of accentuated line occurrence displayed in Figure six reflect early life events that had downstream impacts on adult decisions around migration. It may be suggested that these NZ adults were more buffered from childhood stresses than their contemporaries that remained at home and thus were eligible for migration, and that doing so provided opportunity to improve their circumstances. Conversely, the adults that remained in the UK may have been deprived of the opportunity to migrate, found their prospects improved locally, or were simply not motivated to migrate.

4.5. Limitations and Other Considerations

The analysis of anonymous archeological remains, while providing beneficial data, also comes with unique challenges. It should not be assumed that the individuals here represent the wider population; however, through a combination of historical, archeological and bioarcheological data, aspects of their lives can be determined. This study incorporates 62 samples representing 49 predominantly anonymous individuals (Figure 6). Accordingly, the results presented here reflect early life conditions that had at least indirect downstream impacts on adult working‐class people in a global nineteenth century context. Nevertheless, these data contribute to a growing body of literature exploring the hardships experienced by lower classes during and because of the British Industrial Revolution, a group whose voice is often absent from the historical record. Future research combining datasets from working‐class United Kingdom archaeological assemblages would strengthen the conclusions made in this study.

4.6. Conclusions, Key Takeaways, and Future Directions

This study presents novel observations of dental formation disruption as a proxy of childhood physiological stress in a lower‐class cemetery assemblage from New Bunhill Fields, Southwark, London. The inclusion of teeth that had been previously sectioned for other analytical techniques minimized destructive testing and created a dataset that is directly comparable to data produced through other analytical methods, such as isotope analyses (Esposito et al. 2024). This analysis presents the first direct dental comparison of nineteenth century migrants to a British colony (Otago, New Zealand) with their contemporary origin population. These data indicate potential disparities in early life embodied physiological stress experiences in British colonial subjects who emigrated away from or remained in England. Notably, the lower occurrence of accentuated lines in teeth forming between birth and approximately 2.5 years of life in adult migrants to New Zealand, compared to adults interred in London, may be reflective of the health controls that dictated eligibility for free or supported migration at this time.

Author Contributions

Hallie Buckley: funding acquisition, writing – review and editing, supervision. Anne Marie E. Snoddy: conceptualization, funding acquisition, writing – review and editing, supervision, methodology, resources, validation. Lucy A. Kavale‐Henderson: conceptualization, investigation, funding acquisition, writing – original draft, methodology, validation, formal analysis, data curation, writing – review and editing, visualization. Claire Cameron: writing – review and editing, supervision. Jo Buckberry: conceptualization, writing – review and editing, data curation, resources. Carolina Loch: methodology, conceptualization, writing – review and editing, supervision, validation. Charlotte King: writing – review and editing, supervision. Peter Petchey: funding acquisition, writing – review and editing. Hannah Koon: data curation, resources, writing – review and editing.

Funding

This work was supported by the Ministry of Business, Innovation and Employment, 21‐UOO‐01 and University of Otago.

Ethics Statement

Histological work with NZ samples was approved by the University of Otago Human Ethics Committee (25/1244). Sampling permissions for individuals from NBF Cemetery were provided by MOLA (Museum of London Archaeology) and BARC (Biological Anthropology Research Centre, University of Bradford). Appropriate disinterment licenses and archaeological authorities for work on the New Zealand cemeteries were obtained with the guidance of Megan Callaghan (Health Protection Officer at Public Health South) and Matt Schmidt/Pam Bain (Heritage New Zealand). Formal consultation was undertaken with Aukaha (on behalf of the relevant Kāi Tahu rūnaka), and the Anglican, Presbyterian, and Catholic churches. Destructive sampling for this project was minimized to protect the integrity of these remains while maximizing the scientific information that could be produced (DNA, histology, chemical analyses). We continue to communicate our findings to descendant groups, local communities, and the wider public. These kinds of data allow us to understand the individual hardships experienced by those coming to New Zealand; communication of these stories therefore has the potential to allow descendants and stakeholders to truly identify with and understand their forebears.

Supporting information

Table S1: Summary of Sampled Individuals from New Bunhill Fields Burial Ground, Southwark, London.

Table S2: Summary of Sampled Individuals from St John's Anglican Burial Ground, Milton (SJM), Ardrossan St Cemetery, Lawrence (AS) and Drybread Cemetery (DB) in Otago, New Zealand.

Table S3: Daily Secretion Rates for Individuals from New Bunhill Fields Cemetery, London. Enamel was divided into cuspal and lateral regions, and further divided into thirds across the enamel thickness, designated “inner”, “middle” and “outer”. These are abbreviated as Cuspal Inner (CI), Cuspal Middle (CM), Cuspal Outer (CO), Lateral Inner (LI), Lateral Middle (LI) and Lateral Outer (LO).

Table S4: Daily Secretion Rates for Individuals from the New Zealand Cemeteries. Enamel was divided into cuspal and lateral regions, and further divided into thirds across the enamel thickness, designated “inner”, “middle” and “outer”. These are abbreviated as Cuspal Inner (CI), Cuspal Middle (CM), Cuspal Outer (CO), Lateral Inner (LI), Lateral Middle (LI) and Lateral Outer (LO). Where the enamel region was absent, n/a is recorded.

Table S5: Minimum Counts of Accentuated Lines Visible in the Enamel of Subadults from NBF.

Table S6: Minimum Counts of Accentuated Lines Visible in the Enamel of Adults from NBF.

Table S7: Minimum Counts of Accentuated Lines Visible in the Enamel of European Adults interred in New Zealand between Birth and 30 months of age.

Figure S1: Chronology of Accentuated Line (AL) formation in European Adults from New Zealand. Horizontal gray bars represent the approximate age at which the preserved enamel was forming based on dental histological observation of enamel incremental markers. Vertical red lines indicate the approximate age of AL formation (representing an episode of physiological stress experienced).

Table S8: Average Number of Accentuated Lines observed in each age band organized by demographic group.

Table S9: Proportion of Individuals in which at least one accentuated line was observed per two‐month period of enamel development.

Table S10: Summary of Age‐At‐AL formation for Individuals from New Bunhill Fields Cemetery. All ages are given in calendar days before/after formation of the NNL.

Data Availability Statement

The data that supports the findings of this study are available in the Supporting Information of this article.