mind than of nature. Taxonomists—specialists in biology who describe and name species—frequently disagree over where one species ends and a similar one begins. At the molecular level, where genes function, boundaries are even less clear. Fundamental metabolic processes are similar in all living things, and biotechnological research overwhelmingly vindicates Darwin's thesis that species share much in common as a result of common origins. Even the apparently solid boundary between plant and animal kingdoms is perforated. For example, many species of plants have genes for producing animal hormones and enzymes, which they make as defenses against mammals and insects that feed on them.

New combinations of genes in microbes are likely to produce dangerous and uncontrollable mutant germs. The possibility of genetic engineers inadvertently making dangerous new microbes does exist, but it is a small risk. Disease-causing organisms are often very specialized, and microbes engineered in the lab for particular purposes are unlikely to out-compete their wild relatives if they should "escape." Virulent diseases such as AIDS, flu, bubonic plague, and Ebola all developed naturally, and genetic engineering is unlikely to produce anything worse. Another possibility is that genetic engineers could deliberately create harmful new germs, but those who choose to develop germs as weapons can do so with or without biotechnology.