Lingual fungiform papillae and teh evolution of the primate gustatory system
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Among humans, the density of lingual fungiform papillae (DFP) is correlated with taste sensitivity. The purpose of this dissertation was to investigate the evolution of the primate gustatory system through a comparative analysis of DFP. This investigation was conducted in three separate studies. The first study took a broad perspective incorporating data from 37 primate species to assess the relationships among DFP, body mass, taste sensitivity, and diet. Among the major findings of this first study: (1) Sucrose sensitivity was negatively correlated with DFP and positively correlated with papilla area. (2) Sucrose sensitivity was not correlated with the percent of leaves or fruit in the diet. (3) DFP and papilla area were correlated with diet. (4) The relationships between fungiform papillae and diet differed among different taxonomic groups. The second study of DFP investigated whether there are sex differences in the DFP of non-human primates, as there are in humans. In all five primate species investigated, females had higher mean DFPs than males. These sex differences were significant in Pan troglodytes and Cebus apella, and not significant in Alouatta palliata, Cercopithecus aethiops, or Varecia variegata. Pan, Cebus, and Homo share large relative brain sizes with associated life history parameters making each offspring very costly. Accordingly it was suggested that sex differences in DFP may be due to the particularly high risk of lacking nutrients or ingesting toxins for females of these three species. The third study was a comparison of phenylthiocarbamide (PTC) taste ability and DFP in humans and chimpanzees. The major questions addressed in this study were (1) Is DFP correlated with PTC phenotype in chimpanzees as it is in humans? (2) Are there sex differences in PTC genotype and phenotype as there are in DFP? Although females had greater DFPs than males, and significantly more females had the genotype for higher PTC taste sensitivity, there was no correlation between DFP and PTC phenotype. Several explanations for the differences between human and chimpanzee results were offered, including small sample sizes for chimpanzees and greater accuracy in determining PTC sensitivity among humans.