Andy Coghlan October 14, 2010
A study of Egyptian mummies and ancient skeletons has found little evidence that they suffered from cancer. The authors of the study suggest that this means cancer is a modern disease.
"This might be related to the prevalence of carcinogens in modern societies," write Rosalie David of the University of Manchester, UK and Michael Zimmermann of Villanova University, Pennsylvania. Cancers, they add, are "limited to societies that are affected by modern lifestyle issues, such as tobacco use and pollution resulting from industrialisation".
The assertions have dismayed cancer researchers, and have led to a rash of uncritical coverage. So what should we make of the evidence from the mummies, and do they justify laying the blame for cancer firmly on modernity? New Scientist investigates.
What did the study find?
In a review of published analyses of tens of thousands of ancient skeletons and hundreds of mummies, David and Zimmermann found only a handful of cases of cancer. One recent finding, of colorectal cancer, was identified as the first ever discovered in a mummy. They also examined ancient texts and literature from Egypt and Greece, and say that there's little sign that cancer was a common ailment.
Is this the basis of their suggestion that cancer is a modern disease?
Yes. Modern lifestyles, and exposure to many more carcinogens than in antiquity.
How have cancer charities and research organisations reacted to the conclusions?
They are not happy. A quote from David put out by the University of Manchester saying "There is nothing in the natural environment that can cause cancer. So it has to be a man-made disease, down to pollution and changes to our diet and lifestyle" caused particular consternation.
What's so wrong with that?
There are dozens of natural causes of cancer, including ultraviolet light from the sun, natural radiation from radionuclides such as radon in rocks, and infection by viruses that trigger cancer, such as the human papilloma virus, which causes cervical cancer and hepatitis viruses that can cause liver cancer. Likewise, soot and smoke from fire contain a multitude of carcinogens, as do fungal aflatoxins deposited on peanuts. "And that's to say nothing of cancers caused by genetic inheritance," says Kat Arney of Cancer Research UK.
But aren't there elements of modern life that cause cancers?
Yes, indeed, but most of them are down to poor lifestyle choices that people can do something about, not, as implied, because they are drowning in a sea of carcinogens from which there is no escape.
Smoking is the most significant of these, causing around a quarter of all cancers globally. "Those deaths could be avoided by a complete ban on smoking," says Joachim Schüz, head of the section on environment and radiation at the International Agency for Research on Cancer in Lyon, France, which evaluates all potential cancer risks.
Other major lifestyle factors that pose cancer risks include heavy drinking, which can lead to liver and gullet cancers, sunbathing, which can lead to skin cancer, and obesity and lack of exercise, which can promote cancers of the gut. "Pesticides and some industrial chemicals can cause cancer, but their overall contribution is very small," says Schüz.
Is there anything else wrong with the study?
Almost all the mummies and skeletons were of people who died before the age of 50. "Ageing is one of the major causes of cancer," says Schüz. He dismissed as "weak" the authors' argument that they could find evidence for other diseases of ageing, such as arthritis and hardening of the arteries, and that cancer should therefore have shown up too. "In men today, 90 per cent of cancers occur after 50," he says. "So if you examined the bodies of 1000 modern men who died before 50, you wouldn't find many cancers either."
Any other gripes?
Yes. One of the main arguments for cancer being an affliction of modernisation was the apparent lack of evidence for "common" bone cancers in children. But again, the figures don't bear this out. "It's true it's a relatively common cancer, but even still it only affects 1 in 10,000 children," Schüz says. "So even if you have 10,000 childhood mummies, you'd be lucky to find one."
David concedes that these are valid criticisms. "We're not saying what the explanation is, we're proposing it's modern living also taking into account that people living longer might be to blame," she says.
What do cancer charities say about the potential impact of the study?
Their big fear is that by blaming industrialisation generally for cancer, it will make people feel helpless about the situation, and divert attention from the many changes they can make to their behaviour to reduce their risk, such as quitting smoking, exercising more, drinking less and eating more healthily.
And what of the history of cancer? Are there other accounts?
Yes. The American Cancer Society has a very accessible account, and there's more information on the Cancer Research UK site and their response to the story here.
Journal reference: Nature Reviews Cancer, DOI: 10.1038/nrc2914