Trouble at the Border: Reframing the Paleobiogeographical Debate over Wegener’s Theory of Continental Drift as a Problem of Paleontology’s Greater Integration with Evolutionary Biology

Abstract

Why did George Gaylord Simpson (1902-1984), probably the most consequential paleontologist of his generation, at first reject the theory of continental drift when, according to Alfred Wegener (1880-1930) who first proposed the theory in 1915, some of the most compelling evidence for drift was paleontological?

In The Rejection of Continental Drift (1999), Naomi Oreskes argued that the comparative geological methods of the paleontologists and stratigraphers were “old” forms of evidence, already mired in long standing theoretical debates and subject to “a priori assumptions” about its inability to decisively rule between competing theories.

This thesis will argue that a more complete answer for Simpson and other paleontologists’ rejection of Wegener’s theory can be found by reframing the debate as a problem of disciplinary integration. In philosophy of science, integration refers to the coming together of different scientific fields for interdisciplinary research. Paleontology, I suggest, should be reframed as a ‘border science.’ I adopt this term to describe the unique positioning of paleontological work at the border between two disciplines: biology and geology. Redefining paleontology as a scientific discipline in terms of its boundary status highlights the competing demands that have historically been placed on paleontological evidence by the ‘parent’ disciplines.

This thesis will argue that the best answer to the question of why paleontologists failed to reach a favorable consensus on continental drift necessitates a critical evaluation of the differing epistemic standards in biology and geology that informed early twentieth century paleontological work. I suggest the following: paleontologists involved in the drift debate were divided over how best to integrate evolutionary theory into paleontological practice and that this was the major source of their confusion.

I compare paleobotanists’ analysis of the distribution of Glossopteris, a Permian-aged genus of seed plants, with vertebrate paleontologists’ analysis of the distribution of the large land fauna of the southern hemisphere. I show how the two groups’ differing approaches to climate, temporality, and how to assess the similarity of lifeforms, were a product of their closer ties to either geology or biology, respectively, and that this positioning greatly influenced their analysis. I conclude that, as a ‘border science,’ integrative efforts to bring paleontology more in line with the rest of evolutionary science also meant an initial loss of epistemic authority for paleontology’s more traditional evidentiary role within geological research. For the history of paleontology, my research suggests that the traditional demarcation of biologically focused work in paleontology as ‘paleobiology’ obscures the broader consequences that a greater integration with evolutionary biology has had on paleontology as an entire discipline. My perspective also adds to the growing literature on the philosophy of integration by suggesting that fields peripheral to those fields being integrated (i.e. geology, for this thesis), whether through pre-existing epistemic commitments or institutional structures, are integral in directing the course of the integration process.