How to build a sea-urchin: simulations as smoking guns

Adrian Currie (Cambridge University)

Abstract

The echinoderms are an ancient lineage whose modern-day representatives include sand-dollars and sea-urchins. In the deep past, echinoderms were much more diverse. Prior to the end of the Paleozoic (around 250 million years ago), echinoderms boasted a wide variety of morphologies. What happened? In this paper, I’ll examine how the use of simulations and other models can help resolve questions about the deep past: that they can act as ‘smoking guns’. Carol Cleland’s notion of a ‘smoking gun’ refers specifically to new trace evidence which empirically discriminates between hypotheses about events in the deep past (the discovery of shocked quartz at the K-Pg boundary, for instance, favoured extra-terrestrial impact over mass volcanism occurring at the time). By developing simple geometric models of echinoderm development, paleontologists are able to examine under what conditions lead to various body-forms. I’ll argue that such results can provide genuine evidence which can distinguish between historical hypotheses: that is, that they are smoking guns. Simulations, then, can generate evidence about the past in a way analogous to (but not, I’ll argue, exactly the same as) observational evidence.