EVENTS

STOQ 2009 – THE STOQ INTERNATIONAL CONFERENCE ON
«BIOLOGICAL EVOLUTION. Facts and Theories»

Abstracts of the Lectures:

Jean Gayon, University of Paris 1, France

History of Evolution Theories

Since 1859, evolutionary biologists have been haunted by the question of whether their conceptions are or are not ‘Darwinian’. Although these terms are ambiguous, the repeated reference to Darwin has a theoretical signification. Darwin settled a conceptual framework that has canalized evolutionary research over one-and-a half centuries. The two major aspects of this framework (the hypotheses of descent with modification and natural selection) will be confronted with further evolutionary research, with special regard to the last 50 years. We propose a classification of the criticisms addressed to Darwin’s two fundamental hypotheses.
In The Origin of species, the postulates underlying Darwin’s hypothesis of "descent with modification" are expressed in a branching diagram, which has generated over time three major criticisms: rejection of gradual modification, rejection of a conception of change exclusively concentrated at the level of the species, and more radical objections regarding the very idea that genealogy can be represented through a unique "tree".
The natural selection hypothesis itself has been criticized at two levels: the level that Darwin called the "mere hypothesis", and that of a "principle" able to explain and unify the whole theory of the history of life. At the first level, three controversies have dominated since the 1960s: controversies over the neutral theory of molecular evolution, controversies over group selection, and controversies over the limits imposed by complexity and self-organization. At the second level (Darwin’s "well-grounded theory"), contemporary evolutionary biologists have challenged Darwin’s idea that natural selection does account for as many "independent classes of facts" as adaptation, extinction, divergence, geological distribution of fossils, geographical distribution of species, relations between embryology and evolution, and patterns of classification.

Contemporary evolutionary biology admits that natural selection is the only acceptable explanation for adaptation, has raised serious doubts about the ability of natural selection to be an all-sufficient principle for the explanation of some or all the other classes of facts that Darwin explained through this principle.
In conclusion, we take S.J. Gould's successive and ambivalent attitudes regarding "Darwinism". In 1980, Gould claimed that Darwinism was "dead". In his Structure of evolutionary theory (2002), he had a more nuanced appreciation, where Darwinism had not been either "extended" or "replaced", but "expanded. In Gould’s terms, "expansion" means a reformulation of the fundamental principles of Darwinism, through generalization of the main
Darwinian processes and addition of new principles. We conclude that the Darwinian framework has persisted, not under the form of the particular models of descent of modification and natural selection had in mind, but in the sense of high level heuristic postulates that have constrained and canalized the possible theoretical choices accessible to evolutionary biologists and paleontologists.