Incisification of anthropoid deciduous mandibular canines.

Interspecific variation of the deciduous mandibular canine's mesial cristid in 51 anthropoid taxa is assessed. In 84% of the taxa observed, mesial cristids were well developed and provided incisor-like occlusion with di2. In 5 of the remaining 8 taxa, lingual cristids provided incisor-like occlusion with dc1. Comparisons between dc1s and C1s of conspecific adult males and females show that in 85% of the species observed the magnitude of mandibular canine incisor traits follows this order: deciduous > adult female > adult male. This within-species variation is inversely related to the likely adaptive value of the canine as a weapon and to canine crown height. A selection model based on these data is derived and applied to human canine evolution. The relevance of these data to the field vs. clone theory debate about dental development is also discussed.