This is the title of an article published in Nature Reviews Cancer. It is an “opinion piece” – a review that puts forward a particular viewpoint, backed up by evidence from the scientific literature. The aim is to be provocative, to stimulate discussion among the relevant community of experts. Sometimes an exchange of published letters to the journal might result. All very civilized and the sort of exchange of views that helps keep thinking sharp and prevent fields stagnating. All very academic.
This particular article stimulated far more discussion than the authors, Rosalie David (Professor and Director of the KNH Centre for Biomedical Egyptology at the University of Manchester, UK) and Michael Zimmerman (an anthropologist at the University of Pennsylvania, USA) could have ever imagined. I wonder what these two senior and well respected academics thought as their academic article turned into lurid headlines sent screaming across the world’s media. “Cancer is purely man-made, say scientists…”. And then the backlash: “Claims that cancer is only a ‘modern, man-made disease’ are false and misleading” huffed Cancer Research UK. “Cancer is not a disease of the modern world” puffed New Scientist.
One almost feels sorry for David and Zimmerman. What their article actually says is that there is a paucity of evidence for the widespread occurrence of cancer in antiquity. This is based on a variety of sources from a lack of descriptions of cancer in ancient art and literature to a lack of evident tumours in mummified remains. At the end of their article they make the following cautious conclusion: “Despite the fact that other explanations, such as inadequate techniques of disease diagnosis, cannot be ruled out, the rarity of malignancies in antiquity is strongly suggested by the available palaeopathological and literary evidence. This might be related to the prevalence of carcinogens in modern societies”. It is this last sentence that has been seized upon and inflated to mean that modern life has caused cancer.
But David and Zimmerman are not entirely innocent. For a start, they contributed to a highly inflammatory press release published on the University of Manchester's website. “Scientists suggest that cancer is man-made” was the slightly less cautious headline. One can almost hear news-hounds around the world sharpening their pencils. And then, perhaps carried away with their moment in the spotlight, they contributed statements to the press release that at best are downright wrong and at worst are plain misleading. “There is nothing in the natural environment that can cause cancer” trumpeted Professor David, “So it has to be a man-made disease, down to pollution and changes to our diet and lifestyle.” Er, UV radiation? Radon? Viruses and bacteria causing cervical cancer, stomach cancer etc.? Professor Zimmerman joined in the fun: “The virtual absence of malignancies in mummies must be interpreted as indicating their rarity in antiquity, indicating that cancer causing factors are limited to societies affected by modern industrialization”. This neatly overlooks the fact that human lifespan in antiquity was much less than today and that age is a major factor in terms of the prevalence of cancer. It is also at odds with the rather more balanced discussion of the age-factor in their paper. Naturally, the critics jumped on these errors and used them to discredit the article.
It is a shame, because they may well be on to something. Unfortunately, they have picked the wrong modern risk factors. Environmental carcinogens caused by industrialization are not the problem here. As Cancer Research UK says: “The evidence that pollution and industrialization have a widespread role in UK cancer rates is weak”. On the other hand, there is a wealth of evidence suggesting that lifestyle factors – smoking, booze, poor diet, lack of exercise – are major risk factors in a large number of cancers. The ‘Western’ lifestyle is just plain unhealthy.
So while it may be that age is also a factor, could it also be true that the rarity of cancer in ancient civilization could be put down to an avoidance of the worst of modern Western excesses? And what if, in the absence of those lifestyle excesses, cancer is no longer an inevitable consequence of age? Surprising as this may seem, it appears that neither ageing nor cancer are an inevitable consequence of long life. Take plants, for example. Despite being exposed to the full range of industrial carcinogens and pollutants, plants neither suffer from cancer (apart from the specific case of crown gall which is disease caused by a bacterial pathogen) nor age. Amazingly, even the most venerable of long-lived trees are as hale and hearty as they were as mere saplings (Penuelas & Munne-Bosch, 2010) still capable of producing new cells at an undiminished rate and apparently resistant to the accumulation of mistakes and errors that bring about our slow decline. It seems that it is not ageing that kills perennial plants, but changes in environment or physical damage. So, if ageing is not inevitable in biological organisms, then might it be possible that we humans could learn the trick? Is there hope for those who yearn for immortality after all? Well, it would take more than a change of lifestyle, but even that would be a start.
