Darwin, the Modern Synthesis, and a New Biology

Any attempt to provide a coherent alternative evolutionary narrative to standard Darwinian tenets should offer a brief overview of the progression of scholarly thought about evolutionary mechanisms. All narratives focus on Charles Darwin's seminal “On the Origin of Species” (Darwin 1859). When Darwin offered that influential work in 1859, he was unaware of the existence of genes. He was a naturalist with a gift for scrupulous observation. Based upon his studies, he proposed the major dictums that have since guided evolutionary thoughts. He offered two linked primary arguments. Evolution proceeded by a process of natural selection through the gradual modification of inherited variations. Notably, the concept of natural selection was not original to Darwin. In 1831, a Scottish horticulturalist, Patrick Matthew had proposed a theory of natural selection, and Darwin was acquainted with his work (Rampino 2010). Another English naturalist and explorer, Alfred Russel Wallace was in communication with Darwin prior to his publication of On the Origin of Species. His correspondence with Darwin had outlined a deliberate mechanism for evolution that incorporated the concept of natural selection. However, it was Darwin's considerable reputation in the scientific community that gave an effective voice to this explosively controversial theory and energized its broader intellectual scrutiny. In this manner, Darwin was substantially adding to an already existing and lively debate. The nineteenth century French naturalist, Jean-Baptiste Lamarck also believed in evolution, and argued that it proceeded through natural laws. He and his many advocates proposed that individuals could inherit characteristics from their ancestors based on the patterns of use of the various faculties (Bowler 2003). For example, the long necks of giraffes were thought to be due to the stretching of their necks to reach high branches of trees. Darwin did not specifically disagree. He had espoused a variant of Lamarckism that he termed “pangenesis” in his 1868 text, Variation in Plants and Animals Under Domestication. A German biologist, Ernst Haeckel, added his own form of support in the 1870s with his well-known “ontogeny recapitulates phylogeny” hypothesis (Bowler 2003). He proposed that the stages of development of an embryo conformed to successive stages of its ancestral evolutionary development. Further reinforcement for this position emerged in the latter part of the nineteenth century through Wilhelm Haeckel's proposal of “orthogenesis.” Strenuously promoted by the German zoologist Theodore Eimer, orthogenesis was the process by which an organism directed toward a determined course by internal forces. In that circumstance, variation is not random, and selection need not be preponderant since a species is carried forward automatically by inner dynamics (Fox and Wolf 2006). Although the concept that one biological mechanism builds upon another in a non-random manner fell into substantial disfavor in the twentieth century, its basic validity has been resurrected on the basis of modern research in cell–cell signaling (Torday and Miller Jr 2017). It can be seen, then, that evolution has been the subject of intense and longstanding debate. Vigorous controversies remain about the primacy of natural selection, the role of acquired characteristics, sources of variation, and whether or not the evolution is random.