orthogenesis
noun
or·tho·gen·e·sis
ˌȯr-thə-ˈje-nə-səs 
: variation of organisms in successive generations that in some especially former evolutionary theories takes place in some predestined direction resulting in progressive evolutionary trends independent of external factors
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The various models proposed for the mechanism of evolution, such as Lamarckian evolution, orthogenesis, and use-disuse, all implied some level of teleology, that there was a directionality inherent in the process.
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Mano Singham, Scientific American, 5 Sep. 2021
Sperm structure and motility in the eusocial naked mole-rat, Heterocephalus glaber: a case of degenerative orthogenesis in the absence of sperm competition?
—Ed Yong, Discover Magazine, 4 Dec. 2011
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Mano Singham, Scientific American, 5 Sep. 2021
Sperm structure and motility in the eusocial naked mole-rat, Heterocephalus glaber: a case of degenerative orthogenesis in the absence of sperm competition?
—Ed Yong, Discover Magazine, 4 Dec. 2011
Cite this Entry
“Orthogenesis.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/orthogenesis. Accessed 4 Nov. 2025.
Copy CitationMedical Definition
orthogenesis
noun
or·tho·gen·e·sis
ˌȯr-thə-ˈjen-ə-səs
plural orthogeneses
-ˌsēz
: variation of organisms in successive generations that in some evolutionary theories takes place in some predestined direction and results in progressive evolutionary trends independent of external factors
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