Tasmanian devils are known as ferocious predators. Maybe too ferocious! Devils are threatened with extinction by a very unusual cancer, devil facial tumor disease (DFTD). Unlike almost all other cancers, DFTD spreads from animal to animal - it is transmitted when they fight and bite each other. The disease affects the faces and mouths of the animals, making it impossible for them to eat and ultimately killing them.
Incredibly, these amazing animals may be saved by evolution itself. Biologists studying the devils have discovered that they are becoming resistant to the cancer. Looking at thousands of genes, they found hundreds that seem to be changing in response to DFTD. This doesn't happen within a given animal, but babies that inherit good combinations of genes have a better chance of surviving and passing those on to their offspring. Over time, the good combinations of genes become more common in the population. Whether this will happen quickly enough to save the devils is unknown.