Abstract

The present thesis, compatible with Darwinian theory, endeavours to provide original answers to the question of why the evolution of species leads to beings more complex than those existing before. It is based on the repetition of two main principles alleged to play a role in evolution towards complexity, i.e. "juxtaposition" and "integration". Juxtaposition is the addition of identical entities. Integration is the modification, or specialisation, of these entities, leading to entities on a higher level, which use the previous entities as units. Several concrete examples of the process are given, at the genetic level (introns), at the anatomical level and at the social level. Structures where integration at one level leaves the units at a lower level in a state of relative autonomy can be describedusing the metaphor of the "mosaic", and the description can also be applied to the human brain and functioning of thought, where essential functions such as language or memory have a mosaic structure.