Cancer may be a man-made disease caused by our modern behaviors, says a controversial British study. After testing ancient Egyptian remains and finding almost no evidence of cancer, University of Manchester researchers have concluded that humans must be responsible for the widespread disease. Did we bring cancer on ourselves?

How could cancer be man-made?
Today, one in three people will suffer from cancer during their lifetimes. Yet the researchers tested hundreds of Egyptian mummies from a period stretching thousands of years, and found cancer in only one. So something happened with the dawn of the industrial age that made cancer rates rise, say the scientists. "There is nothing in the natural environment that can cause cancer," says Professor Rosalie David of Manchester University. "It has to be a man-made disease, down to pollution and changes to our diet and lifestyle."

What changes could be to blame?
The study notes that evidence of "distinctive tumors" began in the mid-18th century, when British snuff users and chimney sweepers began respectively developing scrotal and nasal cancers. As society became increasingly able to afford to smoke tobacco, eat foods, and drink alcohol to excess, cancer rates crept higher. Of course, says Tom Chivers at The Daily Telegraph, there is another "obvious difference between modern lifestyles and ancient ones" — we live up to 40 years longer than they did, on average. Given that "cancer is overwhelmingly a disease of aging," perhaps we ought to take claims that no cancers were found in ancient remains with a pinch of salt.

Is this the only problem people have with the study?
No. British charity Cancer Research called the study's claims "confusing and misleading," partly because you can't equate ancient lifestyles with our own. But a more striking problem is that the researchers' claim that there are no natural causes of cancer is "simply untrue." Exposure to the sun can cause cancer, and so can bacteria, viruses, and even naturally-occurring chemicals like radon — a radioactive gas that can give you lung cancer. In short, says the charity, "the evidence that pollution and industrialization has a widespread role in U.K. cancer rates is weak."

Why are cancer activists so worried about this study?
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. 

Sources: Daily Mail, The Daily Telegraph, LiveScience, Cancer Research UK