What teeth from a centuries-old cemetery can teach us about climate shocks and disease
A centuries-old cemetery is shedding light on how climate shocks may have contributed to disease during the Industrial Revolution. Britain’s farming-based economy transformed itself into a manufacturing...
A centuries-old cemetery is shedding light on how climate shocks may have contributed to disease during the Industrial Revolution.
Britain’s farming-based economy transformed itself into a manufacturing powerhouse, roughly between 1760 and 1840. During this period, heavy mining and burning of coal to fuel factories and railways blanketed cities in dark smog.
This pollution, alongside hard working conditions, cramped housing and little time spent outdoors limited the sunlight people received.
Sunlight provides the UVB light the skin uses to make vitamin D, which the body needs for bone strength.
Rickets, where the growing skeleton fails to properly mineralise, was common among children. For years, this was attributed to urbanisation, latitude and socioeconomic drivers.
But industrialisation occurred during the Little Ice Age, a cooling period lasting from around the 13th to the 19th centuries. It is attributed mainly to dips in solar activity and frequent volcanic eruptions, which release sunlight-blocking aerosols. New research suggests these natural climate shocks may have been an overlooked contributor.
Scientists analyse teeth from abandoned cemetery
Researchers have reassessed teeth from a long-disused cemetery in northeast England called Coach Lane to investigate whether climatic fluctuation (shifts in Earth’s temperature, rainfall and atmospheric conditions) contributed to childhood vitamin D deficiencies during that time.
“Most people buried at Coach Lane lived during periods affected by environmental differences in UV light availability, which may explain the high rates of rickets and defects in tooth dentin, and suggest a major problem with vitamin D deficiency,” says Dr Ellen Kendall, an archeological researcher at Durham University and first author of the study.
“Realising that burial registers would allow us to reconsider the climatic chronology of this population felt like a new approach to understanding historical childhood vitamin D deficiency.”
Researchers analysed 30 teeth from 21 unidentified individuals who were buried at the cemetery between 1711 and 1829. Around that time, the region was beginning to change from a fishing village into an industrial port.
The researchers examined mineralisation failures. This is when dentin, the inner layer of the tooth, fails to fully turn into hard, calcified tissue.
These defects are common and can have several causes, so on their own they don’t prove vitamin D deficiency. But they may point to a seasonal shortage if they appear at roughly yearly intervals and are separated by normal dentin.
Because teeth form and grow on a set natural schedule, the researchers could determine at what ages dentin failed to mineralise within the community: from early life to early adulthood in some individuals.
Earlier studies of the skeletons at the site found rickets in 44 per cent of the young people examined.
Climate instability is 'nothing new’
The cemetery’s burial register contained the ages and years of death for 109 community members. Because these dates could not be matched to individuals – as the graves weren’t marked – the researchers looked at the community as a whole.
Data showed that out of the 109 people with known birth years, 91 were born during or within 10 years after a large volcanic eruption. Of those, 41 were born during periods when low solar output and volcanic activity co-occurred.
While the study doesn’t attempt to measure how much climate shocks altered the amount of UV light reaching northeast England, Dr Kendall says the team is “fairly confident” that climate was an important contributing factor to vitamin D deficiency in the 18th and 19th centuries, particularly through colder temperatures that changed how people behaved.
The paper hypothesises that two effects may have combined: volcanic aerosols and low solar output reduced the UV light reaching the ground, while cold, wet summers likely kept children indoors and more heavily wrapped up, limiting skin exposure further.
But the researchers stress this was not the only or even the primary cause of vitamin D deficiencies. UV availability, rainfall and temperature interacted with class, diet, occupation, latitude and pollution.
“Archaeology doesn’t often offer certainties,” Dr Kendall says. With so many interacting factors, the researchers say they can only offer explanations consistent with the available evidence. They argue that climate has been overshadowed by industrialisation and urbanisation in previous explanations of vitamin D deficiency.
Taking climate variability – both natural and human-caused – into account is therefore important for building a more complete picture of the factors that shaped people's health.
“We think of climate instability as a modern challenge, but it’s really nothing new as human problems go,” Dr Kendall explains.
“Whether it’s pandemics, economic crises or climate change, it’s important to understand the ways that people have adapted to similar issues in the past and use that information to help people thrive in the future.”
