I'm at the National Association of Science Writers conference this weekend and, in a panel on creating narrative in journalism, author George Johnson mentioned something absolutely fascinating. Johnson is currently writing a book about cancer and he told the audience a story about traveling out to see specimens that showed a metastasized cancer in the fossilized bones of a dinosaur.

I think Johnson just sold me a copy of his book, but I also wanted to look up this phenomenon right now. I'd honestly never heard of dinosaur cancer, but it turns out that there are several examples of this, including a fossilized brain tumor discovered in 2003. That said, there does seem to be some debate on the subject. While that brain tumor was found in the skull of a relative of the T. Rex, another study published the same year found that only duck-billed dinosaurs seemed to have had much of a risk of cancer. In that study, scientists x-rayed 10,000 specimens. They only found cancer in the duck-billed hadrosaurs.

Now, on the one hand, this might not be totally representative of all cancer risk. After all, what you're seeing in fossils are cancers of the bone, or cancers that have metastasized to the bone. On the other hand, if this is an accurate reflection of the nature of cancer in dinosaurs, it's a pretty interesting finding, which suggests that genetics played a huge role in determining which dinosaurs got cancer and which didn't. Either that, or duck-billed dinosaurs were exposed to some kind of environmental risk factor that didn't affect other species. (Which isn't a totally crazy idea. For instance, we know that hadrosaurs grazed heavily on conifers. And, according to the 2003 paper, they may have been the only dinosaurs who preferred that diet.)

There's lots of good stuff to read on this:
Read the full 2003 study on the epidemiology of cancer in dinosaurs
• In 1999, the same researchers published a short report on bone cancer in dinosaurs. You can read that online, too
• A 2007 paper compared rates of bone cancer in dinosaurs with those in modern vertebrates. According to this research, the rate of bone cancer hasn't changed.
• A 2010 paper looked at modern cancer treatments in the context of what we know about cancer in ancient times — both in dinosaurs and in human mummies

Edit: Yesterday, I said David Quammen was the author writing a book about cancer. That was incorrect. It is fixed now.