Rough-skinned Newts (Taricha granulosa) are extremely toxic: the average newt has enough tetrodotoxin (TTX) to kill 30 human beings. But several populations of Common Garter Snake have evolved to be able to tolerate the toxins — in fact, they’re the only predators who can eat Rough-skinned Newts and survive. Molecular biologists have now documented the process by which newt toxins have forced evolutionary changes in the garter snakes that try to prey on them — an ecological arms race at the molecular level.