Do Homoiologies Impede

Phylogenetic Analyses of the Fossil

Hominids? An Assessment based on

Extant Papionin Craniodental

Morphology

Posted: February 13, 2006

The full article can be found here.

"Stephen J. Lycetta and Mark Collardb, c, Corresponding Author Contact Information, E-mail The Corresponding Author

aLeverhulme Centre for Human Evolutionary Studies, Department of Biological Anthropology, University of Cambridge, Cambridge, United Kingdom
bDepartment of Anthropology and Sociology, University of British Columbia, Vancouver, British Columbia, Canada
cAHRB Centre for the Evolutionary Analysis of Cultural Behaviour, University College London, London, United Kingdom

Received 8 June 2004; accepted 8 July 2005. Available online 25 August 2005.

Abstract:

Homoiologies are phylogenetically misleading resemblances among taxa that can be attributed to phenotypic plasticity. Recently, it has been claimed that homoiologies are widespread in the hominid skull, especially in those regions affected by mastication-related strain, and that their prevalence is a major reason why researchers have so far been unable to obtain a reliable estimate of hominid phylogeny. To evaluate this “homoiology hypothesis,” we carried out analyses of a group of extant primates for which a robust molecular phylogeny is available—the papionins.

We compiled a craniometric dataset from measurements that differ in their susceptibility to mastication-related strain according to developmental considerations and experimental evidence. We used the coefficient of variation and analysis of variance with post hoc least significant difference comparisons in order to evaluate the variability of the measurements. The prediction from the homoiology hypothesis was that dental measurements, which do not remodel in response to strain, should be less variable than low-to-moderate-strain measurements, and that the latter should be less variable than high-strain measurements. We then performed phylogenetic analyses using characters derived from the measurements and compared the resulting phylogenetic hypotheses to the group's consensus molecular phylogeny. The prediction was that, if the homoiology hypothesis is correct, the agreement between the craniometric and molecular phylogenies would be best in the analyses of dental characters, intermediate in the analyses of low-to-moderate-strain characters, and least in the analyses of high-strain characters.

The results of this study support the suggestion that mastication-related mechanical loading can result in variation in hominid cranial characters. However, they do not support the hypothesis that homoiology is a major reason why phylogenetic analyses of hominid crania have so far yielded conflicting and weakly supported hypotheses of relationship. These findings are consistent with a recent test of the homoiology hypothesis using craniodental data from extant hominoids, and cast doubt on the validity of the homoiology hypothesis, as originally formulated.

Keywords: Phylogeny; Homoplasy; Phenotypic plasticity; Phenotypic variation; Homoiology; Strain; Mastication; Cladistics; Hominid; Papionin

Corresponding Author Contact InformationCorresponding author. Department of Anthropology and Sociology, University of British Columbia, 6303 NW Marine Drive, Vancouver, British Columbia, Canada, V6T 1Z1. Tel.: +1 604 822 4845; fax: +1 604 822 616."