When THAT Rule Almost Persists as THAT Rule

In biology, theories are constantly enriched and adapted by new examples and scientific advances. In this chapter, we focus on the debate about the rules in biology and their persistence over time as rules accepted by the scientific community. We exemplify this with Darwin’s theory of natural selection, which has been nourished by new disciplines and technologies during the twentieth and twenty-first centuries and has undergone transformations, although it undoubtedly remains the dominant explanation of the evolution of biological systems. Biological rules are dynamic, although they tend to remain relatively stable over time, and their response to the appearance of exceptions can be variable, although the integration of new knowledge into the field is usually gradual until the accumulation of exceptions is so significant that the applicability of the rules is questioned (crisis sensu Kuhnian revolution of scientific knowledge). We illustrate this concept by analyzing the historical evolution of biological species concepts, and we draw attention to the extrapolation of rules originally proposed for certain organisms and applied indiscriminately to other groups without exhaustive testing (e.g., eco-geographic rules).