Could one not say that, in the fortuitous combinations of the productions of nature, as there must be some characterized by a certain relation of fitness which are able to subsist, it is not to be wondered at that this fitness is present in all the species that are currently in existence? Chance, one would say, produced an innumerable multitude of individuals; a small number found themselves constructed in such a manner that the parts of the animal were able to satisfy its needs; in another infinitely greater number, there was neither fitness nor order: all of these latter have perished. Animals lacking a mouth could not live; others lacking reproductive organs could not perpetuate themselves… The species we see today are but the smallest part of what blind destiny has produced…
In his book Systeme de la Nature (1751), he theorized on the nature of heredity and how new species come into being. He thought that speciation took place by chance events in nature, rather than by spontaneous generation as was believed at the time.
Some historians of science see this series of conjectures as an early version of the theory of evolution. Indeed, if Maupertuis had taken his conjectures forward and developed them into a more fully formed theory, he might now be recognised as putting forward the foundations of the theory of evolution. Darwin’s fame rests on being the first to develop and publish the concept as a well-supported scientific theory, rather than being the first to suggest the concept.
Despite his many accomplishments, Maupertuis was considered arrogant by many of his fellow countrymen. He became a target of German mathematician Samuel Koenig, who accused him of plagiarism, and of French author Voltaire, whose satirical writings about Maupertuis were so savage that Maupertuis eventually left France. In 1759, Maupertuis died in virtual exile in Basel, Switzerland, in the home of Swiss mathematician Johann Bernoulli.