John Huss

Methodology and Ontology in Microbiome Research

Research on the human microbiome has generated a staggering amount of sequence data, revealing variation in microbial diversity at the community, species (or phylotype), and genomic levels. In order to make this complexity more manageable and easier to interpret, new units—the metagenome, core microbiome, and enterotype—have been introduced in the scientific literature. Here, I argue that analytical tools and exploratory statistical methods, coupled with a translational imperative, are the primary drivers of this new ontology. By reducing the dimensionality of variation in the human microbiome, these new units render it more tractable and easier to interpret, and hence serve an important heuristic role. Nonetheless, there are several reasons to be cautious about these new categories prematurely “hardening” into natural units: a lack of constraints on what can be sequenced metagenomically, freedom of choice in taxonomic level in defining a “core microbiome,” typological framing of some of the concepts, and possible reification of statistical constructs. Finally, lessons from the Human Genome Project have led to a translational imperative: a drive to derive results from the exploration of microbiome variation that can help to articulate the emerging paradigm of personalized genomic medicine (PGM). There is a tension between the typologizing inherent in much of this research and the personal in PGM.

Paleontology: Outrunning Time

In this paper, I discuss several temporal aspects of paleontology from a philosophical perspective. I begin by presenting the general problem of “taming” deep time to make it comprehensible at a human scale, starting with the traditional geologic time scale: an event-based, relative time scale consisting of a hierarchy of chronological units. Not only does the relative timescale provide a basis for reconstructing many of the general features of the history of life, but it is also consonant with the cognitive processes humans use to think about time. Absolute dating of rocks, fossils, and evolutionary events (such as branching events on the tree of life) can be accomplished through the use of radiometric dating, chronological signals extractable from fossil growth patterns, and the “molecular clock.” Sometimes these different methods of absolute dating, which start from largely independent assumptions and evidentiary bases, converge in their temporal estimates, resulting in a consilience of inductions. At other times they fail to agree, either because fossils and molecules are giving temporal information about different aspects of nature and should not be expected to agree, or because of flawed assumptions that give rise to an inaccurate estimate. I argue that in general, despite the fact that it can be difficult to integrate disparate kinds of evidence, the principle of total evidence should be applied to the dating of evolutionary events. As a historical science, paleontology studies past events we cannot observe directly. This raises questions of epistemic access, meaning that due to the fragmentary nature of the fossil record we may find ourselves without access to the relevant traces to adjudicate between rival hypotheses about the past. The problems and prospects of epistemic access are explored through a case study of the reconstruction of the colors of dinosaurs. The paper closes with a reflection on the Darwin-Lyell metaphor of the fossil record as a highly fragmentary history book, and a call for a reconsideration of the book metaphor in favor of a systems view of the geologic and fossil records.

Popular Culture and Philosophy: Rules of Engagement

The exploration of popular culture topics by academic philosophers for non-academic audiences has given rise to a distinctive genre of philosophical writing. Edited volumes with titles such as Black Sabbath and Philosophy or Buffy the Vampire Slayer and Philosophy contain chapters by multiple philosophical authors that attempt to bring philosophy to popular audiences. Two dominant models have emerged in the genre. On the pedagogical model, authors use popular culture examples to teach the reader philosophy. The end is to promote philosophical literacy, defined as acquaintance with the key problems, ideas, and figures in the history of philosophy. In contrast, on the applied philosophy model, authors use philosophy to open up new dimensions of the popular culture topic for fans. The end is to illustrate the value of philosophy in understanding the popular culture topic, and ultimately, to demonstrate the value of philosophy in general. Taking stock of the relative strengths and weaknesses of these two models provides an opportunity to reflect more broadly on whether, why, and how philosophers should engage the public.