Abstract

CADENA MONROY, LUIS ALVARO. On a New Proposal of the Evolutionary Process. Acta biol.Colomb. [online]. 2009, vol.14, suppl.1, pp.217-230. ISSN 0120-548X.

Some pitfalls of three currently accepted evolutionary approaches are discussed: gradualism, neutralism and punctuated equilibrium. Though two of them refer to change rates, and the other one (neutralism) refers to the absence of selection at the microscopic level, these three proposals are considered due to the relevancy that they have in the context of the bibliography on evolution. An approach is sketched that integrates them and solves the weaknesses of each one. I suggest that the evolutionary process has two fundamental phases. In the first one, organisms create their ecological niche. This is a period of -reverse selection-; in which organism have the initiative. Later, a second phase of -normal selection- is set up, and it is the newly created niche that selects among variant organisms (normal selection). This latter process is possible, only if the period of -reversed selection- can be framed into a more general trend of evolutionary change. I discuss two proposals in which the notion of -reverse selection- is applied: the evolutionary origin of chordata and the evolution towards Homo sapiens.

Keywords : selection; selective direction; hierarchical development; niche formation.

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