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Introduction Paleontologists often reconstruct the sequence of eruption of teeth of fossil mammals (e.g., Stehlin, 1912; Gregory, 1920; Kellogg, 1936; Lamberton, 1938; Tattersall and Schwartz, 1974; Wallace, 1977; Kay and Simons, 1983; Gingerich, 1984; Lucas and Schoch, 1990; Smith, 1994; Martin, 1997). Evolutionary studies, however, have contradictory traditions about the meaning of such sequences. One tradition is that sequence of tooth eruption is a good phylogenetic character, capable of showing genetic relatedness among species (e.g., Tattersall and Schwartz, 1974; Schwartz, 1974; Byrd, 1981), and thus presumably non-adaptive or conservatively adaptive. A second school of thought is that sequence of eruption is an adaptive characteristic: either reflecting dental morphology (e.g., Slaughter et al., 1974), or facial architecture (Simpson et al., 1990), or life history (Schultz, 1935, 1956). Indeed Schultz saw the eruption sequence of teeth as highly adapted to rate of post-natal growth. The obvious question is, does sequence of tooth eruption inform us of species taxonomic affiliation, dental function, facial form, or life history? One approach to the question is to re-examine Schultz's hypothesis on the adaptive nature of tooth eruption sequence. Here, Schultz's ideas are tested against newly gathered data on primates and ungulates, with a few additional data on small insectivorous mammals. The dentition in a life-history context Reptiles tend to grow throughout life, changing prey, and prey size slowly over time (Dodson, 1975). To keep pace with growth and changing diet, reptiles erupt multiple waves of simple, ever-larger teeth (see Chapter 13). Mammals, however, share a system of tooth emergence and replacement that accommodates rapid growth to a fixed body size (see Pond, 1977; MacDonald, 1984). [ABSTRACT FROM AUTHOR]

Introduction Evolution proceeds by selection of phenotypic variations (in this case, of functioning dentitions), and so indirectly of the genotypes that produce them. Evidence for the course of evolution is derived largely from the fossil record, and much of it is provided by teeth. To understand evolution we need to know not only what changes have in fact taken place but also why these changes were of advantage in the functional life of the animal and have thus been selected; in other words, what is the adaptive significance of evolutionary change? In this chapter I will review some of the changes of tooth shape that have taken place in the course of primate evolution, and which appear to be explicable as adaptations to changes of function. Dental adaptations may be considered at two levels. First, there are characters that integrate the teeth into a masticatory system, involving the jaws and their muscles. Then there are modifications of the system in adaptation to functional demands. Most often, these demands are put upon the system by the types of foods eaten, and by feeding behaviour, but for some teeth, especially the incisors and canines, these functions may be unconnected with feeding (for example, grooming and fighting). Brief introduction to fossil primates Primates were derived from primitive insectivorous eutherians in the Cretaceous, and I will use one of these, Kennalestes (Kielan-Jaworowska, 1968, 1981), as a basis of comparison to show the direction of evolutionary change. The early palaeontological history of primates has recently been reviewed by Rose (1995) and Rose et al. (1994). [ABSTRACT FROM AUTHOR]