Chapter 8: Instinct

Rather than defining instinct strictly, the text characterizes it as complex actions performed without experience or knowledge of their purpose, such as the migratory patterns of birds or the architectural precision of insects. While acknowledging similarities between instinct and habit, the focus remains on how natural selection preserves and accumulates slight, profitable variations in behavior over generations. Through the examination of domestic animals—including the specific breeding of pointers and retrievers—it is shown that mental traits can be inherited and modified. The chapter delves into remarkable natural cases, such as the parasitic nesting habits of cuckoos and the varying degrees of slave-making behaviors found in different ant species, illustrating that these "wonderful" instincts are not suddenly created but are the result of gradual transitions. A major highlight is the investigation into the hive-bee's cell-making process; by comparing the simple cells of the humble-bee and the intermediate structures of the Melipona, the text demonstrates that the hive-bee’s geometric perfection is an evolved mechanism to minimize the expenditure of precious wax and labor. Furthermore, the narrative addresses the significant challenge of sterile neuter insects, explaining that natural selection can act on a family or community level to preserve traits that benefit the group, even if the individual cannot reproduce. Ultimately, these diverse behaviors are presented not as specially endowed or perfect creations, but as functional consequences of a singular law governing the advancement of all organic beings through variation and survival.