A genotype:phenotype approach to testing taxonomic hypotheses in hominids
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ORIGINAL PAPER
A genotype:phenotype approach to testing taxonomic hypotheses in hominids Marianne F. Brasil 1,2,3
&
Tesla A. Monson 4 & Christopher A. Schmitt 5 & Leslea J. Hlusko 6,7
Received: 20 April 2020 / Revised: 20 April 2020 / Accepted: 19 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Paleontology has long relied on assumptions about the genetic and developmental influences on skeletal variation. The last few decades of developmental genetics have elucidated the genetic pathways involved in making teeth and patterning the dentition. Quantitative genetic analyses have refined this genotype:phenotype map even more, especially for primates. We now have the ability to define dental traits with a fair degree of fidelity to the underlying genetic architecture; for example, the molar module component (MMC) and the premolar-molar module (PMM) that have been defined through quantitative genetic analyses. We leverage an extensive dataset of extant and extinct hominoid dental variation to explore how these two genetically patterned phenotypes have evolved through time. We assess MMC and PMM to test the hypothesis that these two traits reveal a more biologically informed taxonomy at the genus and species levels than do more traditional measurements. Our results indicate that MMC values for hominids fall into two categories and that Homo is derived compared with earlier taxa. We find a more variable, species-level pattern for PMM. These results, in combination with previous research, demonstrate that MMC reflects the phenotypic output of a more evolutionarily stable, or phylogenetically congruent, genetic mechanism, and PMM is a reflection of a more evolutionarily labile mechanism. These results suggest that the human lineage since the split with chimpanzees may not represent as much genus-level variation as has been inferred from traits whose etiologies are not understood. Keywords Adaptive plateau . Dentition . Early Homo . Hominid evolution . Modularity
Introduction With every discovery of a new hominid fossil comes intense scrutiny of its evolutionary relationship to other hominid taxa (e.g., Chen et al. 2019; Daura et al. 2017; Haile-Selassie et al.
2019; Harvati et al. 2019; Hershkovitz et al. 2018). Phylogenetic systematics is the most widely used approach for inferring these evolutionary relationships (Argue et al. 2017; Dembo et al. 2016; Mongle et al. 2019). This approach assesses a range of characters (i.e., traits) for each of the
Communicated by: Mary T. Silcox Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00114-020-01696-9) contains supplementary material, which is available to authorized users. * Marianne F. Brasil [email protected] 1
Human Evolution Research Center, University of California Berkeley, 3040 Valley Life Sciences Building #3140, Berkeley, CA 94720, USA
2
Department of Integrative Biology, University of California Berkeley, 3040 Valley Life Sciences Building #3140, Berkeley, CA 94720, USA
3
Be
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