Neo-Darwinism is generally used to describe any integration of Charles Darwin's theory of evolution by natural selection with Gregor Mendel's theory of genetics. It mostly refers to evolutionary theory from either 1895 (for the combinations of Darwin's and August Weismann's theories of evolution) or 1942 ("modern synthesis"), but it can mean any new Darwinian- and Mendelian-based theory, such as the current evolutionary theory. The term "Neo-Darwinism" marks the combination of natural selection and genetics, as has been variously modified since it was first proposed.
Darwin's theory of evolution by natural selection, as published in 1859, provided a selection mechanism for evolution, but not a trait transfer mechanism. Lamarckism was still a very popular candidate for this. August Weismann and Wallace rejected the Lamarckian idea of inheritance of acquired characteristics that Darwin had accepted and later expanded upon in his writings on heredity.(p108) The basis for the complete rejection of Lamarckism was Weismann's germ plasm theory. Weismann realised that the cells that produce the germ plasm, or gametes (such as sperm and eggs in animals), separate from the somatic cells that go on to make other body tissues at an early stage in development. Since he could see no obvious means of communication between the two, he asserted that the inheritance of acquired characteristics was therefore impossible; a conclusion now known as the Weismann barrier.
It is, however, usually George Romanes who is credited with the first use of the word in a scientific context. Romanes used the term to describe the combination of natural selection and Weismann's germ plasm theory that evolution occurs solely through natural selection, and not by the inheritance of acquired characteristics resulting from use or disuse, thus using the word to mean "Darwinism without Lamarckism."
Biologists, however, have not limited their application of the term neo-Darwinism to the historical synthesis. For example, Ernst Mayr wrote in 1984 that:
- The term neo-Darwinism for the synthetic theory [of the early 20th century] is sometimes considered wrong, because the term neo-Darwinism was coined by Romanes in 1895 as a designation of Weismann's theory.
Publications such as Encyclopædia Britannica use neo-Darwinism to refer to current-consensus evolutionary theory, not the version prevalent during the early 20th century. Similarly, Richard Dawkins and Stephen Jay Gould have used neo-Darwinism in their writings and lectures to denote the forms of evolutionary biology that were contemporary when they were writing.
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- Gould, Stephen Jay (2002). The Structure of Evolutionary Theory. Cambridge, MA: Belknap Press of Harvard University Press. p. 216. ISBN 978-0-674-00613-3. LCCN 2001043556. OCLC 47869352.
- Beccaloni, George (2013). "On the terms "Darwinism" and "Neo-Darwinism"". A. R. Wallace Website.
- Reif, Wolf-Ernst; Junker, Thomas; Hoßfeld, Uwe (March 2000). "The synthetic theory of evolution: general problems and the German contribution to the synthesis" (PDF). Theory in Biosciences. 119 (1): 41–91. CiteSeerX 10.1.1.329.7230. doi:10.1007/s12064-000-0004-6. ISSN 1431-7613. S2CID 4893208.
- Moran, Laurance (January 22, 1993). "The Modern Synthesis of Genetics and Evolution". TalkOrigins Archive. Houston, TX: The TalkOrigins Foundation, Inc. Retrieved 2007-09-19.
- Bock, Walter J. (July 1981). "Reviewed Work: The Evolutionary Synthesis. Perspectives on the Unification of Biology". The Auk. 98 (3): 644–646. ISSN 0004-8038. JSTOR 4086148.
- Mayr, Ernst (1984). "What is Darwinism Today?". PSA: Proceedings of the Biennial Meeting of the Philosophy of Science Association. 1984 (2): 145–156. doi:10.1086/psaprocbienmeetp.1984.2.192502. ISSN 0270-8647. JSTOR 192502. Volume Two: Symposia and Invited Papers (1984).
- Kutschera, Ulrich; Niklas, Karl J. (June 2004). "The modern theory of biological evolution: an expanded synthesis". Naturwissenschaften. 91 (6): 255–276. Bibcode:2004NW.....91..255K. doi:10.1007/s00114-004-0515-y. PMID 15241603. S2CID 10731711.
- Pigliucci, Massimo (December 2007). "Do We Need An Extended Evolutionary Synthesis?" (PDF). Evolution. 61 (12): 2743–2749. doi:10.1111/j.1558-5646.2007.00246.x. PMID 17924956. S2CID 2703146. Archived from the original (PDF) on 2015-04-24. Retrieved 2011-03-27.
- "neo-Darwinism". Encyclopædia Britannica. Chicago, IL: Encyclopædia Britannica, Inc. 2015. Retrieved 2015-11-19.
- on YouTube. The video of the lecture was originally posted on May 5, 2010, at old.richarddawkins.net: "Lecture on Neo-Darwinism". Archived from the original on December 1, 2014. Retrieved 2013-07-07.CS1 maint: BOT: original-url status unknown (link).
- Gould, Stephen Jay (2011). "Challenges to Neo-Darwinism and Their Meaning for a Revised View of Human Consciousness". In McMurrin, Sterling M. (ed.). The Tanner Lectures on Human Values. 6. Salt Lake City, UT; Cambridge, UK: University of Utah Press; Cambridge University Press. pp. 53–73. ISBN 978-0-521-17647-7. OCLC 846869183. "Lecture delivered at Clare Hall, Cambridge University April 30 and May 1, 1984"