Cuvier/Geoffroy Saint-Hilaire: the quarrel between two brilliant scientists!
The history of science, and that of the Museum in particular, is punctuated with controversies, several of which have remained well-known. One of these is the quarrel between two brilliant minds - Cuvier and Saint-Hilaire - which took on extraordinary proportions in its time.
In 1830, Georges Cuvier and Étienne Geoffroy Saint-Hilaire, two great anatomists from the Museum, clashed in the Academy of Sciences over the question of the unity of living organisms. What is the significance of the shape of organs and the fact that they resemble each across species? For two years there followed a veritable soap opera, with public statements in which one criticised the other's views, relayed by the press and observed at national and international level.
For Cuvier, it is the function of an organ by which it can be interpreted. The sharp molars of a carnivore must correspond to the claws on the end of its legs: functions are correlated with each other at the level of organs that are not necessarily connected. This is the "law of organ correlation". Cuvier distinguished four major levels of organisation of living organisms - vertebrate animals, articulated animals, zoophytes and molluscs - which are so different that they seem irreconcilable. This confirms his creationism.
Conversely, Geoffroy Saint-Hilaire sought fundamental unity among all living things in order to demonstrate the organisation of life according to a single plan. The meaning to be given to an organ is not in its function, but in its connections with neighbouring organs. This makes it possible to trace its origins beyond its forms and functions. He calls 'analogues' organs that are connected to others in the same way in two species, even if their form and function differ. For example, the bat's long, tubular, thin radius and the dolphin's short, massive, flat radius; today we would say 'homologous'. This is the 'theory of analogues'. This brings it close to transformism.
The extreme media coverage of this dispute in France and even in Germany - where the poet, botanist and anatomist Johann Wolfgang von Goethe commented in detail on the episode for his fellow citizens - testifies to the central place that comparative anatomy occupied in the natural sciences at the time, and that of the Museum in international scientific life. Until 1832, when Cuvier died, the two scientists would never cease to confront each other.
This old controversy resurfaced in the 1990s. The discoveries of developmental biology and the emergence of "evo-devo" - a speciality that interprets the genetic control of embryonic development in the light of evolution - shed new light on Saint-Hilaire's work, which influenced embryology, evolutionary biology and palaeontology.