Homosexuals, they claim, have declared war on nature, and nature has exacted an awful retribution. Fundamentalists admit the evolution of a virus as nature's revenge but will not concede that the same process acts upon life as a whole. Even to anti-evolutionists, AIDS is proof of descent with modification because they can see it happening. Its agent has changed in its brief history and has adapted to overcome the many challenges with which it is faced. Darwin would have been delighted to see the workings of his machine so starkly exposed.
Science makes patterns from ideas.
If AIDS can evolve, so can anything else. The Origin uses freshwater bears and flying fish to make a case that applies to all forms of life. For its opponents, in contrast, what is true for viruses cannot be true of birds or fish, let alone a man. The existence of an animal as unlikely as a whale is, for them, proof that evolution does not work. The other view of the origin of whales, men or viruses is simple.