G Gaps in Darwin’s Initial Theory modification.” Second, it argued that this process was driven by natural selection, an evolutionary Geoff Kushnick mechanism co-discovered with Alfred Russel School of Archaeology and Anthropology, The Wallace that required a struggle for existence, Australian National University, Canberra, ACT, variation with fitness consequences, and inheri- Australia tance of that variation. This work remains stand- ing as a centerpiece of current evolutionary thought. Despite this, acceptance of Darwin’s Synonyms work was never smooth sailing, as it faced a mix of criticism and praise from scientific and societal Criticisms of Darwin’s work on natural selection; communities. Some bona fide gaps in the original Shortcomings in the Origin of Species related to theory were exposed by these critiques. Darwin Darwin’s/Wallace’s theory of natural selection was clearly moved by some of the criticism, as is evidenced in the book’s revisions and in his cor- respondence with intellectual contemporaries. Definition Other gaps existed but it is unclear whether Dar- win recognized them. Shortcomings in and criticisms of the theory Ori- By necessity, the coverage of gaps in this entry gin of Species related to Darwin’s/Wallace’s the- is somewhat selective but includes (a) arguably ory of natural selection and how those gaps were the most important gap in the lack of a proper filled. understanding of genetics; (b) gaps of immediate relevance to researchers interested in the evolu- tion of human behavior, including evolutionary Introduction psychology, in the theory’s inability to explain seemingly maladaptive traits; and (c) gaps in the This entry focuses on gaps in the initial theory of macroevolutionary claims in Darwin’s early work Charles Darwin in his 1859 book On the Origin of which are of relevance for understanding the early Species by Means of Natural Selection or the theory’s relevance for human evolution. Preservation of Favoured Races in the Struggle for Life and its six subsequent revisions. This Fleeming Jenkin’s Critique work can be summarized as two major arguments In 1867, Scottish engineering professor, Fleeming (Bowler 1989): First, it argued that species Jenkin (Fig. 1), published a review of Origin of evolved via a process of “descent with Species wherein he advanced a three-part critique © Springer Nature Switzerland AG 2020 T. K. Shackelford, V. A. Weekes-Shackelford (eds.), Encyclopedia of Evolutionary Psychological Science, https://doi.org/10.1007/978-3-319-16999-6_1385-1 2 Gaps in Darwin’s Initial Theory principles, which were published 2 years prior to the publication of Jenkin’s review, but did not receive wide circulation until the turn of the twen- tieth century (Bowler 1989; Charlesworth and Charlesworth 2009; Gayon 1998). This paved the way for the “Modern Synthesis”–a new understanding of evolutionary processes and their consequences based on a tying together of Mendel’s and Darwin’s (and Wallace’s) ideas. Jenkin offered two additional points of criti- cism (Gayon 1998). The second was that variabil- ity within a species was bounded and that natural selection, thus, was insufficient to drive specia- tion. This is discussed in further detail below. The third criticism was that the earth was insufficiently old to have supported the evolution of its diverse life forms. This was a direct refutation of geologist Charles Lyell’s findings, on which Darwin’s the- ory was propped, that the earth was sufficiently old to have allowed “virtually unlimited amounts of time” (p.206) for evolution to have occurred Gaps in Darwin’s Initial Theory, Fig. 1 Fleeming (Bowler 1989). Jenkin’s point here was based on a Jenkin, a Scottish engineer, published a three-part critique ’ of Darwin’s initial theory. Darwin conceded to Jenkin with critique of Lyell s work by Lord Kelvin. Darwin regard to the inheritance of variation but was unmoved by was unconvinced by this part of Jenkin’s criti- his criticism that the earth was insufficiently old. (Henry cism, which was for the best as Kelvin was proved Charles Fleeming Jenkin. Etching by W. Holl, 1884. wrong by advances in early twentieth century Credit: Wellcome Collection. CC BY) physics (Bowler 1989). of Darwin’s ideas (Gayon 1998). The critique Explaining Seemingly Nonadaptive Traits exposed two gaps in the initial theory and another Darwin (1859) viewed his theory as providing a that rested on reasonable-for-the-time theory that mechanism that would favor individually benefi- was later disproved. cial traits, never those that were “injurious to itself The most famous of his criticisms centered on as natural selection acts solely by and for the good the inadequacy of blending inheritance, the mech- of each” (p.201). Explaining the existence, and anism favored by Darwin and his contemporaries, thus evolution, of seemingly nonadaptive traits – for sustaining natural selection (Charlesworth and such as aesthetic displays and altruism – was a gap Charlesworth 2009). Even when a trait confers a in Darwin’s initial theory (Fig. 2). selective advantage, offspring fail to inherit it due Darwin felt that his initial theory could not to the “swamping effect” of blending. Rather, they explain the evolution of exaggerated or purely will inherit a phenotype intermediate between ornamental features on the basis that they their mother’s and father’s. Despite Jenkin’s belief appeared nonadaptive (Bowler 1989; Cronin that this was problematic for the inheritance of 1991; Jones and Ratterman 2009). In a letter writ- small changes, but not large ones (referred to as ten in 1860 to his friend, American botanist Asa “sports”), Darwin’s theory rested on the accumu- Gray, he opined that “the sight of a feather in a lation of small changes. Darwin conceded to peacock’s tail, whenever I gaze at it, makes me Jenkin in subsequent editions of Origin of Species sick!” Darwin presaged his eventual solution to and in a letter to Wallace. Jenkin’s criticism lost its the problem in Origin of Species, but it was in his bite with the eventual acceptance of Mendel’s second major work, The Descent of Man, and Gaps in Darwin’s Initial Theory 3 Gaps in Darwin’s Initial Theory, Fig. 2 Nonadaptive favor these traits when they provide a mating benefit traits posed a problem for Darwin’s initial theory: (a) (as shown on the right). (b) Altruism, defined as behavior extravagant displays, such as the peacock’s train, were that benefits others at a cost to individual fitness, was a viewed as nonadaptive in the context of regular natural problem for Darwin’s original theory that took a century to selection; as shown on the left, they might attract the solve. There is a debate over whether Darwin himself attention of or slow the escape from predators. Darwin recognized it as a problem later elaborated the theory of sexual selection which can Selection in Relation to Sex (Darwin 1871), that gap in the initial theory, and a satisfactory solu- he detailed the theory of sexual selection. In tion, despite being presaged by Darwin and others essence, he argued that it worked via two mecha- following him (Dugatkin 2007), was only offered nisms: female choice (intersexual selection) and with the formulation of inclusive fitness theory in direct male-male competition (intrasexual selec- the later half of the twentieth century. The delay in tion). Darwin and Wallace disagreed about both resolution, though certainly attributable to a mul- mechanisms. Wallace argued that female choice titude of factors, may have been caused to some could not have driven evolution and that traits that degree by the debate over individual versus group may have arisen via male-male competition, such selection (Domondon 2013; Ratnieks et al. 2011). as an elk’s antlers, would evolve via regular nat- ural selection for utilitarian purposes. Although The Origin of Species and Transitional Forms Darwin was correct in essence, and there were The lack of evidence for the second of Darwin’s some advances in the interim, sexual selection main claims, and the element of the theory from did not become part of the canon of evolutionary which derived the name of his most famous theory until the second half of the twentieth cen- work – that natural selection would lead to the tury (Cronin 1991). origin of new species – was an important problem Another problem with Darwin’s initial theory for his theory. Huxley, for instance, who was was its inability to explain the evolution of otherwise one of Darwin’s most vociferous allies altruism – those behaviors that provide a fitness (his “bulldog”), argued that the most conclusive benefit to others while incurring a cost to the actor evidence for selection would come when it can be (Cronin 1991; Dugatkin 2007; Ratnieks et al. shown to “produce a new species” (as quoted in 2011). Altruism includes, of course, traits such Bowler 1989, p. 195). Darwin’s erroneous ideas as alarm calling and providing care to young by about what constituted a species have been parents and others. Darwin singled out the evolu- pointed out as another weakness (Mallett 2008). tion of sterile workers in honeybees, something Nonetheless, Darwin’s ideas about the mecha- that today is viewed through the lens of altruism, nisms that would drive speciation – geographic as posing a “special problem” for his theory isolation – mirror modern ideas on allopatric spe- (Darwin 1859, p.236). While some see this as ciation but downplay the ability of speciation to evidence that he puzzled over the evolution of occur without it, which is today referred to as altruism (e.g., Dugatkin 2007), others argue that sympatric speciation. he never recognized the problem as such (Cronin Another related gap in the initial theory was the 1991; Ratnieks et al.