Surprisingly enough, scientists have found that they can test the hypothesis that some rise in radiation level was related to the demise of the dinosaurs by looking for fossil evidence of a rise in cancer. L C Natarajan and colleagues at the University of Kansas found one example of metastatic bone cancer in a sample of 708 dinosaurs. Based on this result, and comparisons with estimated cancer rates in modern vertebrates, the team concluded that elevated levels of ionizing radiation did not play a significant role in the Cretaceous–Tertiary extinction event 65 million years ago.