Cancer may have killed more than one in 10 adults in medieval Britain, research suggests.
The disease's onset is complex, with both genetics and lifestyle habits often contributing.
While many point the finger at modern-day vices like smoking and environmental toxins, archaeologists from the University of Cambridge found 9% to 14% of adults died with a form of cancer up to 10,000 years ago – around 10 times higher than previous estimates.
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One in two people born after 1960 in the UK will statistically develop cancer at some point in their life.
Writing in the journal Psychiatry Research, a team from the University of Eastern Finland recently reported: "Approximately 5%–10% of all tumour diseases are caused by genetic predisposition.
"The remaining 90%–95% can be explained by environmental conditions and lifestyle, particularly by smoking, alcohol use, obesity and an unbalanced diet, and lack of exercise."
Nevertheless, some cancers are known to run in families.
"For example, your risks of developing certain types of breast cancer, bowel cancer or ovarian cancer are higher if you have close relatives who developed the condition," according to the NHS.
"It's estimated between three and 10 in every 100 cancers are associated with an inherited faulty gene."
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To better understand how cancer rates have changed over time, the Cambridge archaeologists examined 143 skeletons from six medieval cemeteries – from the 6th to 16th centuries – in and around the university city.
All the skeletons had an intact spine, pelvis and thigh bones – the regions most likely to have secondary tumours after an original malignant mass has spread.
"The majority of cancers form in soft tissue organs long since degraded in medieval remains," said lead author Dr Piers Mitchell.
"Only some cancer spreads to bone and of these, only a few are visible on its surface, so we searched within the bone for signs of malignancy."
Cancer that has spread to the bone is considered advanced and often terminal.
Past research only examined outer bones for signs of the disease, suggesting cancer affected less than 1% of the medieval – or "Middle Age" – population.
Using X-rays and CT scans, the archaeologists detected signs of the disease in five (3.5%) of the skeletons.
One skeleton, of a middle-aged man, had lesions throughout, suggesting he had a form of blood cancer.
Past research has shown CT scans detect bone cancer in around three-quarters (75%) of cases.
Based on the fact that a third to half of all cancer deaths involve the disease spreading to bones, the archaeologists have estimated 9% to 14% of medieval Britons developed the disease.
Premature deaths in medieval times were thought to predominantly come down to infectious diseases like dysentery and bubonic plague, along with malnutrition.
"We now have to add cancer as one of the major classes of disease that afflicted medieval people," said co-author Dr Jenna Dittmar.
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Nevertheless, cancer is considerably more common in modern times.
Tobacco – introduced to Europe in 1492 when Christopher Columbus discovered the Americas – is likely highly responsible for the rise in the disease, the archaeologists wrote in the journal Cancer.
Cancer-causing pollutants have been released since the industrial revolution in the 1700s and 1800s.
Travel has also led to a rise in infections. Hepatitis B and C are leading causes of liver cancer, with the latter also linked to non-Hodgkin's lymphoma. The human immunodeficiency virus (HIV) can also trigger tumours of the liver, throat and lungs.
In addition, modern medicine means people live longer, with the risk of cancer rising with age.
The archaeologists have stressed relatively few skeletons were analysed in their study. In addition, "diagnosing cancer in individuals who died hundreds of years ago is clearly a challenge".
"We need further studies using CT scanning of apparently normal skeletons in different regions and time periods to see how common cancer was in key civilisations of the past," said Dr Mitchell.
Understanding how rates of cancer have changed over time helps officials and medics "plan for the future", according to the archaeologists.
"If it [cancer rates] has changed from 9% to 14% of adults in the medieval period to 40% to 50% in modern times, this raises the question as to whether it will continue to increase in prevalence in the future," they wrote.