Lucien Cuénot et la théorie de l’évolution : un itinéraire hors norme

Abstract

Lucien Cuénot and the Evolution’s Theory: an out of Norm Itinerary The French biologist Lucien Cuénot (1866-1951) is famous for the important role he played in the birth of genetics at the beginning of the 20th Century. His experiments, involving mice from 1902 onwards, led to a number of conclusions: the demonstration of the validity of the Mendelian laws for animals and the existence of multiple alleles and lethal genes, among others. Furthermore, the correlation between one gene and one enzymatic activity was illustrated for the first time. This work, whose importance was internationally acknowledged, was all the more noticeable considering Cuénot’s relative isolation in France, a country that only belatedly accepted the burgeoning field of genetics. Yet his large body of work also covered many other fields in biology : animal morphology and physiology, faunistics and the study of animal adaptations and defense mechanisms. A directing line settles its homogeneity: it is the interest in evolution. These well-known studies on the nature of heredity were only first steps on Cuénot’s long journey. In this respect, Cuénot’s thought underwent considerable change during the course of his career. Initially he considered himself a “Darwinian”, though his understanding of the term was different than the more orthodox interpretations of the time. Later, he would pursue an original path between neo-Lamarckism, very widespread in France at the time, and neo-Darwinism. For instance, he changed his position in regards to natural selection. Early on, he considered natural selection as the principal force in the formation of species ; later, he would attribute to it a more limited, and purely destructive, role. The leitmotiv of his subsequent publications was the theory known as “Preadaptation”, which states that a species first has to acquire favorable structures before colonizing a new environment. Thus, during a brief period, Cuénot maintained positions similar to those of mutationnists such as de Vries, who considered that large-extent mutations were capable of producing evolutionary innovations. In the end, however, he questioned the role of chance in the appearance of highly complex organs or sets of intricately-coordinated organs (he called them coaptations). From the 1920s onwards, he came to accept the inability of the biologist to account for adaptation, and he finished by believing in a “mitigated finalism” until the end of his career.