The Portrayal of Industrial Melanism in American College General Biology Textbooks

The phenomenon of industrial melanism became widely acknowledged as a well-documented example of natural selection largely as a result of H.B.D. Kettlewell’s pioneering research on the subject in the early 1950s. It was quickly picked up by American biology textbooks starting in the early 1960s and became ubiquitous throughout the 1970s, 1980s and 1990s. While recent research on the phenomenon broadly supports Kettlewell’s explanation of IM in the peppered moth, which in turn has strengthened this example of natural selection, textbook IM entries have actually declined in recent years in favor of other examples. In a previous paper, we drew attention to the pivotal role visual aspects played in the introduction of IM into textbook accounts. The present article continues this investigation by analyzing textual passages on industrial melanism within a stratified random sample of textbooks from the 1960s to the 2000s. The fact that this example of natural selection was included by multiple publishers independently, in a short period of time, makes it uniquely qualified for a textbook study of this kind. The purpose of the present project was to determine whether these textbooks contain what has come to be known as the standard peppered moth story. Three complete series were also inspected for change across time. Our analysis focused on the amount of text devoted to industrial melanism; what specific science content elements were present; and what, if any, nature of science aspects were included. The study documents an increase in the amount of text devoted to industrial melanism over the decades. In spite of this increase, only modest changes in science content and NOS aspects were found.