Oct 15 2010

Do Mummies Get Cancer?

File this one under – massive and unjustified speculation based upon limited data.

There are multiple news reports of a recent study looking at mummies to see if there is any evidence of cancer. The results:

Professor Rosalie David, a biomedical Egyptologist at the University of Manchester, and a colleague, Professor Michael Zimmerman, searched for evidence of cancer in hundreds of mummies, fossils, and ancient medical texts. One might say that the silence was deafening.

This was an interesting study in medical forensics, but I do not think it is so obvious how to interpret it. The spin in the media is this:

The mummies don’t lie. David concluded that their findings, “along with other data from across the millennia, has given modern society a clear message—cancer is man made and something that we can and should address.”

Slow down – let’s back up a bit. The assumption here is that if cancer occurred in ancient times there would be evidence for it in mummies. The authors are quick to dismiss the obvious factor that people live longer today, and age is the primary risk factor for cancer. The age range of the mummies they examined was 25-50. That’s young. The risk for most cancers really takes off after age 50, and continues to rise with age.

They also mention childhood cancers, but many of those are not solid tumors, but blood-based cancers like leukemia. There would be no tumors to find in a mummy. In any case, there does not appear to be any child mummies in their study.

So I don’t think the age factor can be so easily dismissed. This is not to say that there are not other factors that have increased the risk of certain cancers. Smoking is now common in the world, and is a major risk factor for lung cancer and some other cancers. Industrial exposure (from coal mining, for example) is also a factor.

Diet is often raised as a factor, and there is evidence that a diet rich in fruits and vegetables may be associated with a lower risk of some cancers. But the data is mixed, probably because the effect size is small. The data certainly does not justify blaming the modern diet for a significant increase in cancers. Also, we should not assume that the diet of ancient cultures was superior to the modern diet. It was much more restricted, and relied on a few staples, mostly grains. Today we have access to fresh fruits and vegetable from around the world year round. There are also some negatives to the modern diet, mainly in terms of excess, but it is not obvious how this all shakes out in relation to cancer risk.

Further it should be noted that this study is showing a lack of evidence, which is an inherently weak form of evidence on which to base conclusions. It is evidence, and as I said it may be saying something interesting, but much more thought and research will be needed to figure out exactly what.

Given all this, extrapolating from this mummy study to the conclusion that cancer is a result of modern society is scientifically absurd. But of course that is the dramatic conclusion that the media is going with in their endless effort (or so it seems) to confuse the public on all matters scientific.

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