A recent article published in the October issue of "Nature Reviews Cancer" has been picked up at multiple lay press sites and on the news services. You may have already seen it, as well. In brief, two anthropologists failed to find any evidence of cancer in a review of a large series of mummies and on this basis they concluded that cancer was virtually entirely a man-made disease. This is an interesting but highly flawed premise from several perspectives, as has been pointed out by others in the lay press articles. One wonders about the medical background of the authors.
Quite a few obvious problems rapidly come to mind. First, cancer as a substantial cause of mortality is almost entirely a disease of older age. During the era in which the mummies studied lived, lifespan was extremely short. To live into your early 40's was quite an accomplishment. Our ancestors simply didn't live long enough for cancers to develop in any significant numbers.
Then there's the issue of detection. Many ( most? all?) mummies had their internal organs removed and preserved poorly or not at all. One can imagine that tumors of organs or soft tissues, not causing obvious bone destruction could be difficult or impossible to detect in many mummified specimens.
We know, increasingly, that many relatively common adult tumors such as colon, breast, ovarian, and pancreatic cancers, among others, have a substantial genetic component that almost certainly has existed for many thousands of years. From an evolutionary perspective, genetic defects, in this case oncogenes, that don't express themselves until much later in life when our offspring (ie. our DNA) have passed into independence have little or no evolutionary pressure against them. These genes lay dormant until lifespan increased enough for them to be expressed in significant numbers.
Finally, it is well known that there are many naturally occurring causes of cancer that existed long before the mummies in this study walked the earth. Viruses have been around a LONG time and an increasing number of them are well established causes of human cancers. Just to name a few: HPV, EBV, HHV8, and Hepatitis-B. Sunlight, asbestos, and many other naturally occurring agents are known to be carcinogens.
Even with the above serious issues, however, the study does raise some interesting points worth remembering. Most common and often fatal cancers DO have a significant man-made component. Before the advent of automated cigarette manufacturing, lung carcinomas were so rare as to be medical curiosities. Asbestos, though a natural mineral, did not become a significant cause of malignancies until the industrial age mandated its mining and manipulation into a wide variety of insulating products. Leukemias and thyroid carcinomas have been convincingly linked to radiation exposure from nuclear testing. Adjuvant hormone therapy (estrogens) has been strongly linked to uterine and breast carcinomas And the list goes on. In many of these cases there is probably an associated genetic predilection that on its own was not sufficient to cause malignancies to develop, but the environment was the critical factor.
If all this seems straightforward, it is. And these are the kinds of facts that anyone walking and breathing should probably know.... But if you want to get really depressed, read some of the blog comments on a couple of the lay press web sites regarding this article:
...unfortunately ignorance about basic medicine abounds. One writer in "The Week"
expressed concerns about the article, " Because it could lead people to worry more about "carcinogens in the air or chemicals in their food" than the lifestyle choices that actually can improve your health, says the Telegraph's Tom Chivers. "Smoking, obesity, alcohol, [and] exposure to the sun" are demonstrably bad for your health, and can lead to cancer. "We shouldn't let a few ancient Egyptian corpses" distract us from that."