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[awr-thuh-jen-uh-sis] /ˌɔr θəˈdʒɛn ə sɪs/
  1. Also called orthoselection. evolution of a species proceeding by continuous structural changes in a single lineage without presenting a branching pattern of descent.
  2. a theory that the evolution of a species in a continuous, nonbranching manner is due to a predetermined series of alterations intrinsic to the species and not subject to natural selection.
Sociology. a hypothetical parallelism between the stages through which every culture necessarily passes, in spite of secondary conditioning factors.
1890-95; < New Latin; see ortho-, genesis Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for orthogeneses


  1. evolution of a group of organisms predetermined to occur in a particular direction
  2. the theory that proposes such a development
the theory that there is a series of stages through which all cultures pass in the same order
Derived Forms
orthogenetic (ˌɔːθəʊdʒɪˈnɛtɪk) adjective
orthogenetically, adverb
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Encyclopedia Article for orthogeneses


theory that successive members of an evolutionary series become increasingly modified in a single undeviating direction. That evolution frequently proceeds in orthogenetic fashion is undeniable, though many striking features developed in an orthogenetic group appear to have little if any adaptive value and may even be markedly disadvantageous. A variety of theories have attempted to explain orthogenesis, but with only partial success.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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