International Society for History, Philosophy, and Social Studies of Biology


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Program

MONDAY, JULY 6  /  15:30 - 17:00  /  DS-R340
Organized session / standard talks
Novelty and discontinuity in evolution
Organizer(s):

Thibault Racovski (University of Exeter, United Kingdom)

Evolutionary novelties as opposed to quantitative phenotypic variation and macroevolutionary patterns as opposed to microevolutionary events play strategic roles in current theoretical debates in evolutionary biology, especially with respect to the call for an “Extended Evolutionary Synthesis” (EES) (e.g. Müller & Pigliucci 2010). The core of the Modern Synthesis (MS) was a theory of microevolution, formalized by population genetics as changes of allele frequencies in populations under the influence of natural selection and other population-level forces. The claim that macroevolution can be extraplolated from micrevolution (Simpson, 1953) could solve the problem of novelty. From the 1970s onwards, this picture has been challenged on several fronts: from paleontology, with the theory of “punctuated equilibria” (Gould and Eldredge 1972); from developmental biology, with the study of heterochrony (e.g., Gould 1977) and other regulatory phenomena studied in the context of EvoDevo; from physical theories of self-organization (e.g., Kauffman 1993); and, from studies on the role of symbiosis in macroevolution (Margulis 1970). This session aims to assess the impact of these advances in different biological disciplines on issues related to novelty and macroevolution. These advances led some defenders of an EES to argue that the MS did not have the theoretical means to address these issues (e.g. Pigliucci and Müller 2010). While contributing to a deeper understanding of novelty and macroevolution, the variegated theoretical landscape makes it difficult to formulate a unified framework. A first talk (Huneman) addresses the respective impacts of different challenges (especially biological and mathematical) to the extrapolationist thesis. A second talk (Love) tackles the problem of integrating different approaches to the explanation of novelty, especially the historical and experimental approaches. A third talk (Racovski) addresses ambiguities in the definitions of evolutionary novelty and show how they weaken the case for an EES.


Macroevolution and microevolution: Timescale and modeling in evolutionary biology

Philippe Huneman (IHPST/ Université Paris 1 Panthéon-Sorbonne, France)

According to the Modern Synthesis, population genetics, as the science of the dynamics of changing allele frequencies in a population, is the core of evolutionary biology since it explains the arising of adaptations by cumulative selection. Its scale is microevolution, namely, evolution of the population of one species within a timescale not too large, defined by a small window of variations and environmental changes. Microevolution constrats with macroevolution, that is, a longer timescale that involves large environmental changes such as the extinction or emergence of species and clades. MS claimed that macroevolution is not different from macroevolution. This “extrapolationist” thesis formulated by Simpson (1953) is challenged: by the “punctuated equilibrium” thesis, recently by Evo-Devo, or by biologists highlighting that symbioses – sometimes occurring at the microevolutionary scale - have major macroevolutionary effects (Margulis, 1970). This talk questions why the extrapolationist thesis is threatened by advances in ecology and developmental theory. It essentially distinguishes between biological and mathematical reasons why there could be principled differences between microevolution and macroevolution. The former concern the nature of variation, which fuels natural selection: whether it’s only made up by mutations and sexual recombination, or whether other developmental features should account for phenotypic variation. Mathematical reasons concern the modeling of chance events in microevolution: at larger timescales, models of chance (such as Gaussian distribution of fluctuations) may not be any more justified, and other models would be required, though at microevolutionary timescales all models would be in practice equivalent. This argument relies on the distinction made by mathematician Mandelbrot between “wild randomness” and “mild randomness” as two distinct structures of randomness. I conclude by showing that the mathematical differences between micro and macroevolution are more general, and therefore may challenge the extrapolation thesis even if empirical facts do not support the biological differences.


The centrality of experiment in the historical science research program on evolutionary novelties

Alan Love (University of Minnesota, United States)

Most evolutionary novelties originated long ago in the history of life. Some philosophers have argued that there are key differences between experimental and historical science, such as the latter exhibiting confirmation that relies on explanatory power rather than predictive success (Cleland 2011). Investigations of evolutionary novelties, such as the origin of the tetrapod limb or angiosperm flower, fall into historical science as they concern past events and require an explicit reconstruction of the phylogenetic juncture relevant to the period of origination for a trait (Love 2008). At the same time, most biologists working on explanations of the origin of novelties see their research program as experimental, and this experimental aspect is crucial to its viability as a developmental contribution to evolutionary theory (Wagner 2001). This paper will explore what it means for a historical science research program to be experimental by scrutinizing two different approaches to the origin of novelties developmental genetics and generic, physical mechanisms (Wagner 2014 Newman 2012). The lines that have been drawn between historical and experimental science do not capture the nature of these research programs and the associated scientific inquiry is better interpreted as organized by structured problem agendas that encourage an explicit combination of historical, experimental, and comparative dimensions.


On ambiguities in the definition of evolutionary novelties and their consequences for the debate on the extended evolutionary synthesis

Thibault Racovski (University of Exeter, United Kingdom)

A commonly accepted intuitive definition of evolutionary novelty exists: a new phenotypic trait bringing a qualitative difference, rather than a quantitative one, compared to traits already present in the lineage. However, there are currently several technical definitions of evolutionary novelty in use, some incompatible with each other. In recent years, the search for a unique definition has been criticized as harmful for research (Brigandt & Love 2012). In this framework, the diversity of definitions corresponds to diverse explanatory goals. Furthermore, this search for a unique definition has been overcome by devising typologies of novelties (e.g. Müller 2010). There is however one important reason to be careful in assessing this diversity: the concept of evolutionary novelty is closely related to the debate over the need for an Extended Evolutionary Synthesis (EES). Novelty is often presented as a class of phenomena that is allegedly not fully covered by explanations from traditional evolutionary biology and that demands theoretical changes to be fully addressed (Pigliucci and Müller 2010). In this talk, I argue that the plurality of definitions of novelty is a sign of the weakness of the concept of novelty itself. I focus on the prominent definition of novelties as traits with no homologs (Müller and Wagner 1991), and on subsequent variants of it. I show that among different proponents of this single definition, there are explicit or implicit disagreements on the essential properties of evolutionary novelties (developmental independence, lack of evolutionary intermediates, specific processes of origination). I then argue that these properties are actually independent (one often comes without the others) and that some are not specific to novelties. I end by analyzing the role of the concept of novelty in the defense of an EES and how a weakened concept of novelty affects this defense.