He devised the first modern definition of what a species is - a slightly modified version of which would later become known as the Biological Species Concept in addition he believed that speciation typically occurs in allopatry or parapatry - when diverging populations are geographically separated or abutting. Wallace's contributions to science actually went far beyond 'merely' co-discovering the theory on which modern biology is based (evolution by natural selection). However, Wallace's actual theory (Wallace, 1858) included both of these selective forces (see Smith, 2023), whereas Darwin's focussed on biotic factors (Darwin, 1858). Others (refs to follow), have stated that Wallace's theory was inferior because he believed that natural selection was driven by abiotic factors, such as climate change, whereas Darwin believed it was driven by biotic interactions, such as intraspecific competition. However, this is incorrect, and ironically, it was Darwin who was the group-selectionist, not Wallace (see THIS). Some authors (refs to follow) have argued that "Darwin's theory" of adaptive evolution was superior to Wallace's, because Wallace was a 'group-selectionist'. "Darwin and Wallace's Theory" should be used specifically to refer to their jointly proposed theory of natural selection. It should really be referred to as "Wallace's Theory", since his theory of adaptive evolution excluded Lamarckism. A strong case could be therefore made that Wallace was the first to propose a correct theory of adaptive evolution, since Darwin's 'hybrid' theory was flawed. So, ironically, the phrase "Darwin's Theory", commonly used to describe the modern theory of adaptive evolutionary change due to natural selection minus Lamarckism, is incorrect. As Darwin stated in the 5th edition of Origin "I am convinced that Natural Selection has been the most important, but not the exclusive, means of modification." (Darwin, 1869). Darwin, in contrast, believed that the inheritance of acquired characteristics operated alongside natural selection, and infamously even proposed a mechanism to explain it - his erroneous theory of Pangenesis (for a detailed discussion see Burkhardt, 2023). ![]() In fact he was the first natural selectionist to reject this flawed theory (in his seminal ' Ternate Essay' of 1858) and he was therefore in fact (oddly!), the first neo-Darwinian. Unlike Darwin, Wallace always rejected Lamarckism - the inheritance of characteristics acquired during the life of a parent (for example the enlarged biceps developed by a blacksmith over the course of his career). Theories Devised by Wallace Which Have Withstood the Test of Time (i.e. ![]() ![]() ALFRED RUSSEL WALLACE'S SCIENTIFIC LEGACYÄ«y George Beccaloni, October 2017 (last updated May 2023)
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