It may have been a life lived between a rock and a hard place, but one thing ancient man did not have to think much about was cancer.

Survival had more to do with weathering the elements and finding enough food to get by. Flash forward thousands of years later. These days, cancer is the number two killer in America. Why the difference? Scientists say it has to do with what’s in the environment and in our diets. We’re now seeing the effects of pollution and poor nutrition in dramatic ways.

In a recent study appearing in Nature Reviews Cancer, researchers analyzed numerous sources of human and animal remains dating all the way back to the dinosaur age, including several mummies from ancient Egypt. They looked for any evidence of cancer. They also reviewed the literature available from ancient Greece, a time when early and significant medical investigation flourished.

While there is some evidence of cancer in animal fossils, non-human primates and early humans, the findings consistently showed that the incidents are few and far between. Perhaps people in those days didn’t live long enough to contract cancer. But even those types found often in youth, like bone tumors, were not apparent. And because studies have shown that the mummification process actually enhances preservation of tumors better than normal tissue, these cancers would have shown up even now, if present back then.

Researchers noted that it wasn’t until just two hundred years ago that medical literature specifically identified cancer, coinciding with the Industrial Revolution. That’s compelling evidence, they say, that in many cases cancer is man-made, and that attention must be given to reverse the conditions that are causing the disease.