modern synthesis

Today we understand evolution mainly as a fact about nature, but its historical root is that of an explanation of a much older fact: that the living world consists of different types of organisms. Where did theses species, as they were called, come from? In pre-Darwinian times, God was seen as having created them to be eternal, immutable entities arranged in a linear hierarchy. The Swiss naturalist Charles Bonnet wrote in 1779

Nul changement ; nulle altération ; identité parfaite. Victorieuses des élémens , des temps & du sépulchre, les especes se conservent…

No change; no alteration; perfect identity. Victorious over the elements, time and death, the species are conserved… (p. 231f., my translation)

With Darwin, species became fluid. They changed continually and transformed into each other in a process called evolution. Both evolution and the mechanism by which it was proposed to occur, natural selection, were debatable concepts. Both were, in fact, debated, the latter much longer than the former. But the existence of species as distinct phenotypic categories would not seem to be up for debate, for it was the very thing these two ideas were meant to explain. To change it would be to change the subject. And yet, later history revised the definition of evolution in such a way as to remove the target of explanation after the explanations themselves were already in place. Read More