When you consider a tapeworm or an Ebola virus, it is easy think of them as being evil to their very core. That’s a mistake. It’s true that at this point in their evolutionary history these species have become well adapted to living inside of other organisms (us), and using our resources to help them reproduce themselves even if we get sick in the process. But one of the big lessons of modern biology is that there are no essences in nature–only the ongoing interplay of natural selection and the conditions in which it works. If the conditions change, organisms may evolve into drastically different things. Even the most ruthless parasite may discover the virtues of peace and harmony–if the