Evolution usually receives popular mention in the context of natural history, i.e. "how we got this way". Far less appreciated is the fact that life all around us, even life within us, is constantly continuing to change. The lightening-fast regeneration of bacteria and inspect species allows for dramatic evolution within the scale of weeks, and Unnatural Selection examines the human role in that drama. This is a subject not merely interesting in the abstract, but one with direct connection to our health and our food.
Life is dynamic that responds to stimuli just as a market responds to incentives. The first vaccines against the smallpox bacteria and other microbes revolutionized medicine, allowing it to directly combat disease instead of merely preventing it. They also changed the bacteria, however; within ten years of penicillin's introduction, for instance, resistant bacteria had taken over. Those who could take the punches were the ones who survived to reproduce, and in the decades since medical researchers have been kept busy trying to find ways to keep us ahead in the arms race. While doctors are now beginning to understand the risks of using antibiotics too aggressively, Nature's resilience applies to things we're not trying to kill. Take the flora and fauna of the Hudson River, for instance, turned into a de facto chemical waste depository; though the worst damage has been cleaned, the toxic years live in a resident population of amphibians who are far more resistant to similar invasion than their long-dead cousins. Of course, this doesn't mean we shouldn't clean up our act, since animals that ingest toxic substances can still kill the animals that attempt to digest them, but it's nice to know Nature is a tougher bird than she's given credit. Similar responses are observed in the realm of cancer cells, which are essentially an invasion from within, and in agribusiness as genetically modified crops spread their genetic influence.