Sexual selection in prehistoric animals: misidentifications and false positives
Prof Kevin Padian, Department of Integrative Biology & Museum of Paleontology, University of California, Berkeley
Tuesday 11th December 2012
Neil Chalmers Seminar Room, DC2, NHM, 1330
Darwin acknowledged that the roles of some morphological structures are difficult to determine. But he was clear about what sexual selection is, and the role of sexual dimorphism in it. Because Darwin invented sexual selection, and based it on observations that have never been falsified, his definition cannot be wrong. It has three components: (1) it explains why sexual dimorphism exists, and its central role in sexual selection; (2) the dimorphic structures or behaviours are used by one gender to attract mates or repel rivals for mates; and (3) these structures and behaviours help the bearer gain access to mates. Strangely, palaeontologists and neontologists have largely ignored him. Assertions of sexual selection/dimorphism in the fossil record suffer from a lack of statistical rigor and an unwillingness to test hypotheses through independent lines of evidence. No such study has had any independent assessment of the chronological age or stage of its individuals, although such information is frequently available. We show why much alleged sexual dimorphism in fossil tetrapods is more likely simply ontogenetic change, and why both a statistically significant population sample and an independent assessment of age of specimens are needed before the hypothesis of sexual dimorphism can be tested.
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