This account of the evolution of the food habits of the Hominidæ will probably be condemned by experimentalists, who have adduced strong evidence for the doctrine that "acquired characters" cannot be inherited. But, whatever the explanation may be, it is a fact that progressive changes in food-habits and correlated changes in structure have occurred in thousands of phyla, the history of which is more or less fully known. Nobody with a practical knowledge of the mechanical interactions of the upper and lower teeth of mammals, or of the progressive changes in the evolution of shearing and grinding teeth, can doubt that the dentition has evolved pari passu with changes in food habits. Whether, as commonly supposed, the food habits changed before the dentition, or vice versa, the evidence appears to show that the Hominidæ passed through the following stages of evolution:
1. A chiefly frugivorous stage, with large canines and parallel rows of cheek teeth (cf. Sivapithecus).
2. A predatory, omnivorous stage, with reduced canines and convergent tooth rows (cf. Homo heidelbergensis).
3. A stage in which the food is softened by cooking and the dentition is more or less reduced in size and retrograde in character, as in modernized types of H. sapiens.
The following is an abbreviation of Gregory's arrangement of the Primates (pp. 266, 267).
Order Primates
Suborder Lemuroidea
Suborder Anthropoidea
Series Platyrrhinæ [New World monkeys]
Fam. Cebidæ
Fam. Hapalidæ [Marmosets]
Series Catarrhinæ [Old World monkeys]
Fam. Parapithecidæ [extinct]
Fam. Cercopithecidæ
Fam. Simiidæ
Sub-fam. Hylobatinæ [Gibbons]
Sub-fam. Simiinæ [Simians or Anthropoid apes]
By the courtesy of the author we are permitted to reproduce his provisional diagram of the phylogeny of the Hominidæ and Simiidæ (p. 337).
The following explanation is offered for the convenience of those who may not be familiar with the technical terms here employed.
Simia, the genus containing the orang-utan.