Published online by Cambridge University Press: 04 August 2010
This chapter is intended to be a chapter of ideas, mixing fact with suggestions that, although seemingly logical and based on the previous chapters, might require a lifetime's work to substantiate in any detail. More precisely stated then, it is speculative. When biologists do this (speculate) on the adaptive significance of changes in the form and function of plants and animals by setting these adaptations in an ecological context, they tend to refer to it as a scenario. In keeping with this theatrical jargon, this chapter goes distinctly ‘off-lineage’ at times, mentioning the dinosaurs even, but once the scenery is painted and the script sufficiently advanced, the mammals are swung in for their top billing.
By analogy to the sharpest way of controlling the content of television programmes, those who really do not like it can simply shut the book: there are generalizations beyond redemption here. However, all this stems from the best of intentions, which is to offer new possibilities for explaining some of the major trends in mammalian evolution, trends that are documented very largely via the dentition. I try to portray the evolution of the dentition of mammals in terms of the principles expounded in the previous chapters. However, it would be impossible to cover every lineage and foolish to claim that I can understand the range of forms that exist or have existed on the basis of current knowledge.