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Marsupial lions and methodological omnivory: function, success and reconstruction in paleobiology


Historical scientists frequently face incomplete data, and lack direct experimental access to their targets. This has led some philosophers and scientists to be pessimistic about the epistemic potential of the historical sciences. And yet, historical science often produces plausible, sophisticated hypotheses. I explain this capacity to generate knowledge in the face of apparent evidential scarcity by examining recent work on Thylacoleo carnifex, the ‘marsupial lion’. Here, we see two important methodological features. First, historical scientists are methodological omnivores, that is, they construct purpose-built epistemic tools tailored to generate evidence about highly specific targets. This allows them to produce multiple streams of independent evidence and thus maximize their epistemic reach. Second, investigative scaffolding: research proceeds in a piece-meal fashion, information only gaining evidential relevance once certain hypotheses are well supported. I illustrate scaffolding in a discussion of the nature of functional ascription in paleobiology. Frequently, different senses of ‘function’ are not discriminated during paleobiological investigation—something which can mar adaptationist investigations of extant organisms. However, I argue that, due to scaffolding, conflating senses of ‘function’ can be the right thing to do. Coarse-grained functional hypotheses are required before it is clear what evidence could discriminate between more fine-grained ones. I draw on omnivory and scaffolding to argue that pessimists make a bad empirical bet. It is a bad idea to bet against the epistemic fortunes of such opportunistic and resourceful scientists, especially when we have reason to think we will systematically underestimate the amount of evidence ultimately available to them.

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  1. Although, see Jeffares 2008.

  2. This is, on the face of it, a different kind of success than that which drives arguments about realism/anti-realism. That debate hinges on whether success at ‘saving the phenomena’, that is, empirical adequacy, provides reason to believe in successful theories’ posits. I am interested in how historical scientists generate the amount of knowledge that they do, given the difficulty of their investigative targets.

  3. Of course, the point of demarcation is to understand the success and failure of sciences, and so these discussions are related. However, I am not primarily interested in comparing historical to ahistorical science. Rather, I examine historical science on its own terms.

  4. Reconstructing past organisms is not the only, or even the central, business of paleobiology. More important is study of large-scale macroevolutionary patterns revealed in the fossil record.

  5. For instance, Carey et al. (2011) describes a trackway assemblage from Victoria which may contain a few traces of T. carnifex, however this is quite speculative.

  6. The thought that T. carnifex was arboreal can be traced to Wells and Nichol (1977)’s morphological study. My philosophical point does not rely on which hypothesis about T. carnifex’s locomotive method turns out to be the most plausible: indeed, if I am right about scaffolding, we ought to expect debates like this to drive further discovery.

  7. Recently, Wells et al. (2009) have argued that T. carnifex was a climber after all, pointing to pedal morphology. As they discuss, heavy animals like bears and gorillas can certainly climb trees. This misses the mark: Finch and Freedman’s complaint is not that something as large as T. carnifex couldn’t climb a tree, but that it couldn’t climb a tree in a koala-like manner. Especially in light of Wroe et al. (1999)’s weight estimates, I think this fairly convincing.

  8. See Thomason (1991) for extended discussion of the idealizations made, and their justifications (in particular, estimations using beam-theory are contrasted with independent in vivo tests of bite force).

  9. The centroid of a two dimensional object is (informally) the point at which it would, were it a cardboard cut-out, balance perfectly on the tip of a pencil.

  10. Leah Schwartz has pointed out to me that things are not as cut and dry as they appear: whether such out-competition really occurred is difficult to establish. I don’t think this undermines the philosophical point of the discussion, however.

  11. However, Bennett and Goswami (2013) have since produced further evidence of less disparity across marsupial skulls than placental skulls.

  12. ‘Bracketed’, in reference to ‘phylogenetic bracketing’.

  13. Thanks to Brett Calcott for suggesting the inclusion of the environment. Although the bracketed models considered in T. carnifex reconstruction do not index inferences to environments, some do. Particularly in cases where evolutionary convergences are exploited to support adaptationist hypotheses (see Currie 2013).

  14. For instance, there are many ways of getting around trade-offs and this can make optimality models misleading. Erickson et al. (2004) have argued that T. rex had two distinct ontogenetic stages: a juvenile stage characterized by fast running speeds and feathers, and a slow, featherless adult packing a major bite. They speculate that the animal hunted in packs, the smaller animal catching and harrying prey, allowing their mature conspecifics to catch up for the kill. If there is a tradeoff between size and speed in Tyrannosaurids, this is a way of solving it: although I doubt it would be represented in an optimality model.

  15. See, for example, Brandon (2013), Amundson and Lauder (1994), Griffiths (2006), Cummins (1975), Preston (1998).

  16. A referee points out that that, if pessimists are right and many facts about the past will remain unknown to us, then this defence of functional conflation will be much stronger. There is, then, something of a tension between my argument against pessimism, and my argument that a lack of information about the past can justify conflation. If the former argument is right, the scope of the latter argument will decrease. I don’t see this tension as problematic: even the most optimistic attitude to the historical sciences ought to allow that, at least sometimes, the past will remain hidden—and in those cases, some conflation might be allowable.


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This paper was presented at the 7th Munich-Sydney-Tilburg philosophy of science conference, “Evolutionary Thinking”, as well as at Calgary and Otago Universities. I’m grateful to these audiences for their feedback. Maureen O’Malley, Leah Schwartz and Brett Calcott read drafts and provided incisive, constructive comments. The paper also benefitted greatly from the generous input of two anonymous referees.

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Currie, A. Marsupial lions and methodological omnivory: function, success and reconstruction in paleobiology. Biol Philos 30, 187–209 (2015).

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  • Historical science
  • Paleobiology
  • Function
  • Methodology
  • Scientific success
  • Reconstruction