JERNVALL, Jukka; KANGAS, Aapo; KAVANAGH, Kathryn; SALAZAR-CIUDAD, Isaac; Univ. of Helsinki, Finland; Univ. of Helsinki, Finland; Univ. of Helsinki, Finland; Univ. of Helsinki, Finland: Mammalian dental diversity: so many shapes, so few genes

Why are there so many tooth shapes and why are some dental forms more common than others? Despite the high diversity of tooth shapes, the relatively complete fossil record of mammalian teeth show frequent and parallel evolution of similar morphologies in several mammalian lineages. In most cases we can infer functional and ecological factors that have promoted the evolution of certain morphologies, but are the underlying molecular changes always the same? Based on comparative developmental biology studies, the development of different tooth features in different species involve iterative activation of the same set of genetic pathways. While computer simulations of development suggest that some morphologies may indeed be more likely to evolve because of development, known genetic changes affecting tooth shape have been relatively unknown. Those cases that are known, seem to suggest that simple molecular changes can affect multiple aspects of tooth shape. It is thus plausible, and as suggested by studies on heritable quantitative traits, that the mammalian dental diversity might be developmentally regulated by relatively few genes which have different effects on character covariance.