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

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TUESDAY, JULY 7  /  11:00 - 12:30  /  DS-M440
Organized session / standard talks
Lineages across the life sciences: Epistemological and ontological issues

Celso Antonio Alves Neto (Leibniz Universität Hannover, Germany); Thomas Reydon (Leibniz Universität Hannover, Germany)

The lineage concept is central part of the darwinian framework (Sober, 2003). It represents historical relations among biological entities over generations and, therefore, it plays a central role in classificatory methodology and practice (e.g., phylogenetics). The relevance of lineages in classification influence different research areas. For example, under certain conditions phylogenetic hypotheses help in the process of testing homologous traits in Evo-Devo (Ereshefsky, 2009). Another example concerns “lineages tracing”, an technique that allows a better understanding of cell replication and fate (Kretzschmar, K. & Watt, M, 2012). The relevance of lineages go beyond classificatory practices. Recently, it was suggested that such a concept takes part in the abstract models of stem cells, playing a role in the conceptual foundations of stem-cell research (Fagan, 2013). Lineages also stand in the background of what is called “lineage explanation”, an explanatory pattern that deals with the continuity of change in biological mechanisms across time (Calcott, 2009). Finally, the concept of lineages has been evoked in the context of redefining fitness and natural selection, making selection more sensitive to the evolution of symbionts and ecosystems (Bouchard, 2008). Taking into consideration how widespread the reference to lineages is, a philosophical work consists in clarifying the actual role(s) of this concept across the life sciences. This enterprise can reveal and further explore explanatory patterns, ontological commitments and methodological principles attached to the concept of lineage. In this sense, it is worth asking what this concept does in different biological areas and how it is related to theory and practice in such areas. It is also worth questioning its relation with other pervasive concepts in biology, such as reproduction, populations and biological individuals. The aim of this symposium is to explore such topics, creating an interdisciplinary forum on epistemology and ontology of biological lineages.

The species problem problem and the no solution solution

Matt Haber (University of Utah, United States)

I will be arguing that adopting a Levels of Lineage perspective shifts the species problem to a lineage problem, and that this is a welcome development. It requires that we think of species as multilevel lineages that are studied from a variety of theoretical perspectives. If fragmented fields of biology are tracking overlapping multilevel objects of theoretical interest, then it is an empirical question whether and when these objects align. The patterns of discordance and concordance should be recognized as facts in need of explanation; it is theoretically fruitful to recognize and study when and to what extent these multilevel objects line up. In some cases we should expect discordant groupings, other times consensus. These sorts of research problems encourage understanding how various fields of biology might theoretically and empirically inform each other. To display this final point, I will be considering whether we ought to think of multilevel lineages as heterogeneous individuals, akin to the heterogeneous organism that Thomas Pradeu argues we ought to adopt as a consequence of the central commitments of immunology. Ultimately, though, the adoption of the levels of lineage perspective gives us a way out of the species problem. It helps reveal a prior problem, namely the species problem problem. Recognizing what this is suggests that the lack of consensus about species is likely to be deeply entrenched, with no straight solution forthcoming. Yet there is hope! Recognizing that this is a consequence of species being multilevel lineages, and considering how biologists deal with this state of affairs in practice suggests that no solution may be needed; rather, I will argue that biologists should adopt a no solution solution. This shifts the focus to lineages from species, and moves past entrenched debates while generating new, more fruitful research questions.

Stem cell lineages: Past, present and future

Melinda Fagan (University of Utah, United States)

My talk examines the lineage concept in stem cell biology. The talk is in two parts. In the first, I show that the concept of ‘cell lineage’ is central to stem cell research, both historically and today. Historically, the idea of a stem cell is closely associated with “stem-tree diagrams” expressing 19th century ideas about development and differentiation (Dröscher 2014). These ideas and images are in retained in theoretical discussions of “stem cells and stem lines” by blood cell researchers in the 1960s-70s (e.g., Lajtha 1979). Today, the lineage concept is implicit in the current definition of a stem cell as an undifferentiated cell capable of both self-renewal and differentiation (Fagan 2013). I use this historical survey and present-day characterization to identify features of the cell lineage concept that are robustly associated with the concept of a stem cell, and discuss these features’ significance in light of the entwined therapeutic and epistemic goals of stem cell research today. In the second part of the talk, I consider how the cell lineage concept is transformed in the emerging framework of systems biology. Systems biology is a loosely-affiliated collection of projects unified by emphasis on comprehensive data-sets and a commitment to mathematical modeling of biological processes, including cell development. Though systems approaches have so far made few inroads into stem cell research, this is likely to change in the near future. Traditional and systems concepts of cell development coincide in Waddington’s landscape (1957), a simple model that projects a “stem tree diagram” onto a rugged epigenetic topography. I show how the concept of lineage is reduced, on some prominent systems approaches, to a branchpoint indicating “bistability” (Strogatz 2000). The first part of the talk indicates some cautionary lessons for ‘reductive’ systems accounts of stem cells and cell development.

Lineages as units of evolvability

Celso Antonio Alves Neto (Leibniz Universität Hannover, Germany)

“Evolvability” is a central concept in contemporary evolutionary thinking that concerns how development influences evolutionary change through biased phenotypic variation supply. This concept implies the existence of lineages, since the influence of phenotypic variation manifests itself across generations. Furthermore, evolvability is sometimes defined as the disposition of lineages to evolve towards more or less phenotypic diversity (Sterelny, 2007). In other terms, lineages are sometimes taken to be units of evolvability. This paper identifies and analyses some commitments attached to this idea. Evolvability is often attributed to populations, not to lineages (Love, 2003; Wagner, 2008). This is a semantic disagreement, but a quite revealing one. As a dispositional property, evolvability is a property of a thing at a time and also implies identity through time. Ambiguity comes from overlooking these different but interrelated dimensions in defining “populations” and “lineages”. As I demonstrate, bringing this bi-dimensionality – synchronicity and diachronicity – to the foreground helps to understand the ontological commitments of lineage concepts and reveals flaws in Sterelny's defense of lineages as units of evolvability. Evolvability is also often attributed to homologous traits (Brigandt, 2007). This gives rise to another semantic disagreement, since a different meaning of “units of evolvability” is implied, which I clarify by revisiting the concepts of “units of evolution” and “units of selection”. Sometimes “units of evolvability” is analogous to the former, sometimes to the latter. The semantic disagreement thus reflects an epistemological difference. For instance, the evolvability of homologous traits is related to “lineage explanation”, whereas the evolvability of lineages belongs to evolutionary explanations broadly understood (Brown, 2014). As I show, clarifying semantic disagreements over “units of evolvability” helps to shed light on the nature of biological lineages by revealing ontological and epistemological features of them.