The frailty of adaptive hypotheses for the origins of organismal complexity

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539 Scopus citations


The vast majority of biologists engaged in evolutionary studies interpret virtually every aspect of biodiversity in adaptive terms. This narrow view of evolution has become untenable in light of recent observations from genomic sequencing and population-genetic theory. Numerous aspects of genomic architecture, gene structure, and developmental pathways are difficult to explain without invoking the nonadaptive forces of genetic drift and mutation. In addition, emergent biological features such as complexity, modularity, and evolvability, all of which are current targets of considerable speculation, may be nothing more than indirect by-products of processes operating at lower levels of organization. These issues are examined in the context of the view that the origins of many aspects of biological diversity, from gene-structural embellishments to novelties at the phenotypic level, have roots in nonadaptive processes, with the population-genetic environment imposing strong directionality on the paths that are open to evolutionary exploitation.

Original languageEnglish (US)
Pages (from-to)8597-8604
Number of pages8
JournalProceedings of the National Academy of Sciences of the United States of America
Issue numberSUPPL. 1
StatePublished - May 15 2007
Externally publishedYes


  • Adaptation
  • Evolvability
  • Genome evolution
  • Modularity
  • Population genetics

ASJC Scopus subject areas

  • General


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