Contrary to long-held opinion, cancer can be contagious—and Darwin is to blame, a science reporter told NPR. It turns out cancer cells evolve as species do, and in some rare cases—a cancer affecting Tasmanian devils, two others in dogs and hamsters—the cancers have evolved to allow direct contagion from one host creature to another.
The devils got it from biting each other, and dogs from sex. How did their cancer cells evolve so effectively? Due to a lack of genetic diversity: The devils, for example, were hunted to extinction by Australian dingos and managed to survive in isolated Tasmania. But "we're very far" from cancer being contagious in humans, the writer said. "I think the real point is understanding cancer better."