DISS: Alfred Russel Wallace’s and August Weismann’s evolution: A story written on butterfly wings

A new (2008) dissertation from Jakub Novak (Princeton University):

Alfred Russel Wallace’s and August Weismann’s evolution: A story written on butterfly wings

The topic of this dissertation is the work and careers of Alfred Russel Wallace (1823- 1913) and August Weismann (1834-1914). A Briton and a German, they were pre-eminent evolutionary biologists of their generations. Each contributed an accomplishment that became seminal for modern biology: Wallace was a co-discoverer of natural selection, while Weismann pioneered the concept of the “continuity of germ-plasm,” a theoretical principle that placed the neo-Lamarckian inheritance of acquired characters out of bounds.

This account provides a long biographical view of these accomplishments, examining in detail how Wallace and Weismann worked toward them, and how the principles they discovered affected their subsequent work. However, the story does not end there. Some of Wallace’s and Weismann’s views departed from the theoretical principles they became famous for, or at least from the way those principles are understood today: in 1868, Wallace proposed that important evolutionary processes were guided by spirit “intelligences;” in 1895, Weismann proposed a supplementary concept of “germinal selection” that re-introduced the inheritance of acquired characters into evolutionary theory. Taking into account these seeming departures, as well as a variety of other projects Wallace and Weismann worked on, makes it possible to define their work in a way that transcends their signature discoveries. Wallace emerges as a biologist whose work amalgamated passions for natural history, natural law, and moral and social philosophy; Weismann as a brilliant speculative thinker intent on precisely calibrating the links between the biological processes of development, heredity, and variation.

A special emphasis is placed on Wallace’s and Weismann’s work with Lepidoptera (butterflies and moths), a subject for which they both had a special fondness. They believed Lepidoptera offered an especially suitable material for evolutionary research. As both (coincidentally) expressed it in poetic terms, the story of evolution was “written on butterfly wings.” Yet the story, as best they could read it, did not fully conform to a neo-Darwinian script. Butterfly wings were icons less of idealized evolution than of the theoretical challenges the self-avowed “Darwinians” Wallace and Weismann had to meet, sometimes at the cost of exploring and advocating principles that would be later judged un-Darwinian.

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