IJEE Soapbox: Darwin, malthus, anD movement: a hiDDen assumption in the Demographic founDations of evolution

We all have our heroes. For myself and, I suspect, many ecologists and evolutionary biologists, Charles Darwin is very high up in the pantheon of truly admirable thinkers and human beings. Few other 19th-century scientists produced books that bear close reading and even re-reading today—yet On the Origin of Species and Darwin’s other volumes certainly do. In honor of this Year of Darwin, and to complement the other fine pieces in this special feature of IJEE reflecting on the future of ecology and evolution, in this essay I instead look at the past, returning to a familiar episode in the early history of evolutionary biology. This episode has to do with how the theory of evolution by natural selection first formulated by Darwin and Wallace was—and still is—based on an understanding of the basic principles of demography. In so doing, I will try to bring out a subtle but vital assumption not evident on the surface in accounts of the demographic basis for evolution—an assumption that, as we will see, is even evoked in the celebrated, poetic ending to On the Origin of Species. Darwin in his Autobiography (1892; reprinted 1958) recounts a crucial juncture in his life when he reflected on the fruits of his voyage around the world (pp. 41–42):