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TABLE 5.1 A Summary of Some Common Misconceptions About Evolution and Complexity, and Contrasting Views

Myth

Reality

1. Evolution is natural selection.

Natural selection is just one of four primary evolutionary forces.

2. Characterization of interspecific differences at the molecular and/or cellular levels is tantamount to identifying the mechanisms of evolution.

The resources deployed in evolutionary change reside at the molecular level, but whereas the cataloging of such differences at the interspecific level identifies the end products of evolution, it does not reveal the population-genetic processes that promoted such change.

3. Microevolutionary theory based on gene-frequency change is incapable of explaining the evolution of complex phenotypes.

No principle of population genetics has been overturned by an observation in molecular, cellular, or developmental biology, nor has any novel mechanism of evolution been revealed by such fields.

4. Natural selection promotes the evolution of organismal complexity.

There is no evidence at any level of biological organization that natural selection is a directional force encouraging complexity. In contrast, substantial evidence exists that a reduction in the efficiency of selection drives the evolution of genomic complexity.

5. Natural selection is the only force capable of promoting directional evolution.

Both mutation and gene conversion are nonrandom processes that can drive the patterning of genomic evolution in populations with sufficiently small effective sizes (common in multicellular lineages).

6. Genetic drift is a random process that leads to noise in the evolutionary process, but otherwise leaves expected evolutionary trajectories unaltered.

By reducing the efficiency of selection, random genetic drift imposes a high degree of directionality on evolution by increasing the likelihood of fixation of deleterious mutations and decreasing that of beneficial mutations.

7. Mutation merely creates variation, whereas natural selection promotes specific mutant alleles on the basis of their phenotypic effects.

Mutation operates as a weak selective force by differentially eliminating alleles with structural features that magnify mutational target sizes.



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