Finding only one case of the disease in the investigation of hundreds of Egyptian mummies, with few references to cancer in literary evidence, proves that cancer was extremely rare in antiquity. The disease rate has risen massively since the Industrial Revolution, in particular childhood cancer — proving that the rise is not simply due to people living longer. … 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”. … Hundreds of mummies from all areas of the world have been examined and there are still only two publications showing microscopic confirmation of cancer. (more; HT Kurzweil)

That is from a press release; journal article quotes below. A very thought provoking result, though it would help if, for comparison, they estimated what fraction of modern bones and mummies show evidence of cancer.  It doesn’t fit very well with the observation that natural plant chemicals seem to cause more cancer than artificial chemicals.  So I remain confused. Those quotes:

Cancer still causes 165,000 deaths every year and is second only to cardiovascular disease as a cause of death. … Evidence of cancer in animal fossils, non-human primates and early humans is scarce. Scientific literature has provided a few dozen, mostly disputed, examples in animal fossils. …

Greece. Several authors wrote about cancer (from the fifth century bce to 1300 ce) … The evidence suggests that the Greeks were the first to identify cancer as a specific disease. …

Palaeopathology … In studies of thousands of bones that represent the fossil record of Neanderthal man in Europe, the Stetten II skull bone from Stetten, Germany, (c.35,000 years bp) provides the only example of a lesion (new bone form) that might be related to a neoplasm. …

Tens of thousands of [ancient] skeletons have been examined but only a few diagnoses of possible and/or probable malignancies — based on gross appearance and occasional X-ray scans showing defects in or masses on bones — have been made. Gray specifically noted the total absence of any radiological evidence of malignancy in his survey of 133 mummies. …

The average lifespan of the wealthier classes was between 40 and 50 years, and a lower age-at-death of between 25 and 30 years is shown in palaeopathological studies of non-elite groups. … Many individuals did live to a sufficiently advanced age to develop other degenerative diseases, such as atherosclerosis, Paget’s disease of bone and arthritis. …

Why are ancient tumours rare? … In modern populations, tumours arising in bone primarily affect the young, so a similar pattern would be expected in ancient populations. … Another explanation for the rarity of tumours in ancient remains is that tumours might not be well preserved; however, experimental studies show that mummification preserves the features of malignancy. ..

We propose that the minimal diagnostic evidence for cancer in ancient remains indicates the rarity of the disease in antiquity. Carcinogenic environmental factors have been linked to up to 75% of human cancers, and the rarity of cancer in anti quity suggests that such factors are limited to societies that are affected by modern lifestyle issues such as tobacco use and pollution resulting from industrialization. (more)

Added 20Oct: Karl points us to an article saying “Wild animals die of cancer at about the same rate [as humans today]” and that animal cancer rates have been increasing lately.