Letters to a Young Scientist Read Online Free PDF Page B

and their esters of a kind found in dead insects. For a while my laboratory smelled like a combination of charnel house and sewer. I put minute amounts on dummy ant corpses made of paper and inserted them into ant colonies. After a lot of smelly trial and error I found that oleic acid and one of its oleates trigger the response. The other substances were either ignored or caused alarm.
    To repeat the experiment another way (and admittedly for my and others’ amusement), I dabbed tiny amounts of oleic acid on the bodies of living worker ants. Would they become the living dead? Sure enough, they did become zombies, at least broadly defined. They were picked up by nestmates, their legs kicking, carried to the cemetery, and dumped. After they had cleaned themselves awhile, they were permitted to rejoin the colony.
    I then came up with another idea: insects of all kinds that scavenge for a living, such as blowflies and scarab beetles, find their way to dead animals or dung by homing in on the scent. And they do so by using a very small number of the decomposition chemicals present. A generalization of this kind, widely applied, with at least a few facts here and there and some logical reasoning behind it, is a theory. Many more experiments, applied to other species, would be required to turn it into what can be confidently called a fact.
    What, then, in broadest terms is the scientific method? The method starts with the discovery of a phenomenon, such as a mysterious ant behavior, or a previously unknown class of organic compounds, or a newly discovered genus of plants, or a mysterious water current in the ocean’s abyss. The scientist asks: What is the full nature of this phenomenon? What are its causes, its origin, its consequence? Each of these queries poses a problem within the ambit of science. How do scientists proceed to find solutions? Always there are clues, and opinions are quickly formed from them concerning the solutions. These opinions, or just logical guesses as they often are, are the hypotheses. It is wise at the outset to figure out as many different solutions as seem possible, then test the whole, either one at a time or in bunches, eliminating all but one. This is called the method of multiple competing hypotheses. If something like this analysis is not followed—and, frankly, it often is not—individual scientists tend to fixate on one alternative or another, especially if they authored it. After all, scientists are human.
    Only rarely does an initial investigation result in a clear delineation of all possible competing hypotheses. This is especially the case in biology, in which multiple factors are the rule. Some factors remain undiscovered, and those that have been discovered commonly overlap and interact with one another and with forces in the environment in ways difficult to detect and measure. The classic example in medicine is cancer. The classic example in ecology is the stabilization of ecosystems.
    So scientists shuffle along as best they can, intuiting, guessing, tinkering, gaining more information along the way. They persist until solid explanations can be put together and a consensus emerges, sometimes quickly but at other times only after a long period.
    When a phenomenon displays invariable properties under clearly defined conditions, then and only then can a scientific explanation be declared to be a scientific fact. The recognition that hydrogen is one of the elements, incapable of being divided into other substances, is a fact. That an excess of mercury in the diet causes one disease or another can, after enough clinical studies are conducted, be declared a fact. It may be widely believed that mercury causes an entire class of similar maladies, due to the one or two known chemical reactions in cells of the body. This idea may or may not be confirmed by further studies on diseases believed affected in this manner by mercury. Meanwhile, however, when research is still incomplete, the idea is