Pierre-Paul Grassé (November 27, 1895 in Périgueux (Dordogne) – July 9, 1985) was a French zoologist, writer of over 300 publications including the influential 52-volume Traité de Zoologie.

He abandoned his preparations for the agrégation to accept a position as professor in the École Nationale Supérieure Agronomique de Montpellier (1921), where the department of zoology was led by François Picard (1879–1939).

He submitted his theses, Contribution à l'étude des flagellés parasites, in 1926, and it was published in the Archives de zoologie expérimentale et générale.

Grassé was elected a member of the Académie des sciences on November 29, 1948, in the anatomy and zoology sector and presided over the institution in 1967.

Grassé received numerous honours and titles during his career: commander of the Légion d'honneur, doctor honoris causa of the universities of Brussels, Basel, Bonn, Ghent, Madrid, Barcelona and São Paulo.

Alongside Andrée Tétry, he composed the two volumes dedicated to zoology in the collection Bibliothèque de la Pléiade, published by Gallimard.

In this publication, Grassé introduced the concept of Stigmergy : He also created three scientific reviews: Arvernia biologica (1932), Insectes sociaux (1953) et Biologia gabonica (1964).

Apart from his numerous scientific publications, he published several works popularising science such as La Vie des animaux (Larousse, 1968).

He united many of the greatest French authorities on the question including Lucien Cuénot (1866–1951), Pierre Teilhard de Chardin (1881–1955), and Maurice Caullery.

[4] Grassé presents his arguments against neo-Darwinism in his work L'évolution du vivant (1973), translated into English as Evolution of Living Organisms in 1977.

Against the idea which states that the evolution of living things is the product of their adapting to changes in their environments, he opposes living fossils, meaning species which stopped evolving at some point in time and have remained relatively identical to this day regardless of great climatic or geological changes (he cites numerous examples in Les formes panchroniques et les arrêts de l'évolution, p. 133).

Biologist Theodosius Dobzhansky wrote in a review that Grassé's belief that evolution is directed by some unknown mechanism does not explain anything.

Kitts found this statement unacceptable commenting that "the fundamental issues raised by Grassé's theory of evolution do not even belong to biology, but to some other discipline.