Sameness, novelty, and nominal kinds

Abstract

Organisms and their genomes are mosaics of features of different evolutionary age. Older features are maintained by 'negative' selection and comprise part of the selective environment that has shaped the evolution of newer features by 'positive' selection. Body plans and body parts are among the most conservative elements of the environment in which genetic differences are selected. By this process, well-trodden paths of development constrain and direct paths of evolutionary change. Structuralism and adaptationism are both vindicated. Form plays a selective role in the molding of form.Keywords: adaptation, developmental constraint, evolvability, formal cause, homology, novelty, strategic gene, transposable elements 3 "One simply cannot escape the conclusion that the brain of a rat and a human are actually the 'same' in spite of their obvious differences." (Wagner 1989) Interface Homology, Genes, and Evolutionary Innovation (Wagner 2014; henceforth HGEI) diagnoses a conflict between structuralist and functionalist (or adaptationist) styles of thinking. Functionalists explain organismal traits by their adaptive value whereas structuralists explain why things are the way they are by appeal to structural constraints and capacities. Wagner proposes "to overcome this conflict by addressing a specific biological phenomenon for which the conflict often crystallizes: the question of homology … At its core, the question is whether homologs exist-that is whether they are natural members of the 'furniture of the world' or whether they are only transient traces of the phylogenetic past. In the latter case, they would have no biological, conceptual, or causal significance. In the former case, homologs would have to play a central role among the concepts of evolutionary theory" (ibid. p. 8). Wagner opts for their central importance.For Wagner (2014), "the realization that complex organisms/systems have unique and historically contingent variational constraints and biases paves the way for a seamless unification of functionalist and structuralist agenda" (ibid. p. 19). In this synthesis, conserved structural properties have a causal role in determining how structures vary, and fail to vary, over evolutionary time. Although an olive branch of unification is offered, HGEI is written to correct the myopia and astigmatism of adaptationism. Adaptationists, it is suggested, have belittled, misrepresented and misunderstood structuralists and rapprochement should occur on structuralist terms (as befits the injured party). An 4 adaptationist who describes similar phenomena in functionalist language is likely to feel misrepresented and misunderstood and to insist that rapprochement occur on functionalist terms. And thus, an underlying consensus may be obscured by semantic arguments because human nature is quicker to recognize when we are misunderstood than when we have misunderstood.My adaptationist commentary on HGEI is an attempt to seek areas of consensus with structuralists and identify where different perspectives of th...

Transposable elements: Self‐seekers of the germline, team‐players of the soma

“…Retroviruses may have evolved expression in these tissues as way‐stations for transmission of exogenous retroviruses from mothers to offspring or endogenous retroviruses from offspring to mothers . In this interpretation, regulatory networks of trophoblast and endometrium have been rewired because these tissues were sites of infectious transmission . Future studies should address whether rewiring of regulatory networks by retroviruses, and by TEs more generally, shows predictable variation amongst tissues and whether these patterns provide clues about routes of retroviral transmission.…”