Article

The Evolutionary Origin of Complex Features

Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, Michigan 48824, USA.
Nature (Impact Factor: 41.46). 06/2003; 423(6936):139-44. DOI: 10.1038/nature01568
Source: PubMed
ABSTRACT
A long-standing challenge to evolutionary theory has been whether it can explain the origin of complex organismal features. We examined this issue using digital organisms--computer programs that self-replicate, mutate, compete and evolve. Populations of digital organisms often evolved the ability to perform complex logic functions requiring the coordinated execution of many genomic instructions. Complex functions evolved by building on simpler functions that had evolved earlier, provided that these were also selectively favoured. However, no particular intermediate stage was essential for evolving complex functions. The first genotypes able to perform complex functions differed from their non-performing parents by only one or two mutations, but differed from the ancestor by many mutations that were also crucial to the new functions. In some cases, mutations that were deleterious when they appeared served as stepping-stones in the evolution of complex features. These findings show how complex functions can originate by random mutation and natural selection.

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    • "This is a similar calculation in concept to a measure of phenotypic complexity used previously [5] in population genetics. To examine why certain population sizes evolved larger genomes, we examined the " line of descent " (LOD) of the dominant type [73]. An LOD contains every intermediate genotype between the final dominant individual and the ancestral genotype that initialized each population. "
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