A. H. Keane

Since the first few pages of this book were in print an important memoir on the "Phylogeny of Recent and Extinct Anthropoids with Special Reference to the Origin of Man" has been published by W. K. Gregory (Bull. Am. Mus. Nat. Hist. Vol. XXXV., Article XIX, pp. 258 ff., New York, 1916). As Gregory's lucid statement of the problems involved is based on a prolonged examination of very varied and abundant material we have considered it advisable to present his summary. The chief conclusions, which appear to be of a conservative character, are as follows (p. 341).

The Origin of Man.

1. Comparative anatomical (including embryological) evidence alone has shown that man and the anthropoids have been derived from a primitive anthropoid stock and that man's existing relatives are the chimpanzee and the gorilla.

2. The chimpanzee and gorilla have retained, with only minor changes, the ancestral habits and habitus in brain, dentition, skull and limbs, while the forerunners of the HominidÆ, through a profound change in function, lost the primitive anthropoid habitus, gave up arboreal frugivorous adaptations and early became terrestrial, bipedal and predatory, using crude flints to cut up and smash the varied food.

3. The ancestral chimpanzee-gorilla-man stock appears to be represented by the Upper Miocene genera Sivapithecus and Dryopithecus, the former more closely allied to, or directly ancestral to, the HominidÆ, the latter to the chimpanzee and gorilla.

4. Many of the differences that separate man from anthropoids of the Sivapithecus type are retrogressive changes, following the profound change in food habits above noted. Here belong the retraction of the face and dental arch, the reduction in size of the canines, the reduction of the jaw muscles, the loss of the prehensile character of the hallux. Many other differences are secondary adjustments in relative proportions, connected with the change from semi-arboreal, semi-erect and semi-quadrupedal progression to fully terrestrial bipedal progression. The earliest anthropoids being of small size doubtless had slender limbs; later semi-terrestrial semi-erect forms were probably not unlike a very young gorilla, with fairly short legs and not excessively elongate arms. The long legs and short arms of man are due, I believe, to a secondary readjustment of proportions. The very short legs and very long arms of old male gorillas may well be a specialization.

5. At present I know no good evidence for believing that the separation of the HominidÆ from the SimiidÆ took place any earlier than the Miocene, and probably the Upper Miocene. The change in structure during this vast interval (two or more million years) is much greater in the HominidÆ than in the conservative anthropoids, but it is not unlikely that during a profound change of life habits evolution sometimes proceeds more rapidly than in the more familiar cases where uninterrupted adaptations proceed in a single direction.

6. Homo heidelbergensis appears to be directly ancestral to all the later HominidÆ.

On the evolution of human food habits.

While all the great apes are prevailingly frugivorous, and even their forerunners in the Lower Oligocene have the teeth well adapted for piercing the tough rinds of fruits and for chewing vegetable food, yet they also appear to have at least a latent capacity for a mixed diet. The digestive tract, especially of the chimpanzee and gorilla, is essentially similar to that of man and at least some captive chimpanzees thrive upon a mixed diet including large quantities of fruits, vegetables and bread and small quantities of meat[1352]. Mr R. L. Garner, who has spent many years in studying the African anthropoids in their wild state, states[1353] that "their foods are mainly vegetable, but that flesh is an essential part of their diet." Other observers state[1354] that the gorilla and chimpanzee greedily devour young birds as well as eggs, vermin and small rodents.

Even the existing anthropoids, although highly conservative both in brain development and general habits, show the beginning of the use of the hands, and trained anthropoids can perform quite elaborate acts. At a time when tough-rined tubers and fruits were still the main element of the diet the nascent HominidÆ may have sought out the lairs and nesting places of many animals for the purpose of stealing the young and thus they may have learned to fight with and kill the enraged parents. They had also learned to fight in protecting their own nesting places and young. And possibly they killed both by biting, as in carnivores, and by strangling, or, in the case of a small animal, by dashing it violently down.

We may conceive that the Upper Tertiary ape-men, in the course of their dispersal from a south central Asiatic centre[1355], entered regions where flint-bearing formations were abundant. In some way they learned perhaps that these "Eolith" flints could be used to smash open the head of a small strangled animal, to crack open tough vegetables, or to mash substances into an edible condition. Much later, after the mental association of hand and flint had been well established, they may have struck at intruders with the flints with which they were preparing their food and in this way they may have learned to use the heavier flints as hand axes and daggers. At a very early date they learned to throw down heavy stones upon an object to smash it, and this led finally to the hurling of flints at men and small game. Very early also they had learned to swing a heavy piece of wood or a heavy bone as a weapon. For all such purposes shorter and stockier arms are more advantageous than the long slender arms of a semi-quadrupedal ancestral stage and I have argued above (p. 333) that a secondary shortening and thickening of the arms ensued.

One of the first medium-sized animals that the nascent HominidÆ would be successful in killing was the wild boar, which in the Pleistocene had a wide PalÆarctic distribution.

From the very first the ape-men were more or less social in habits and learned to hunt in packs. Whether the art of hunting began in south central Asia or in Europe, perhaps one of the first large animals that men learned to kill after they had invaded the open country was the horse, because, when a pack of men had surrounded a horse, a single good stroke with a coup-de-poing upon the brain-case might be sufficient to kill it.

I have argued above (p. 321) that the retraction of the dental arch and the reduction of the canines is not consistent with the use of meat as food, because men learned to use rough flints, in place of their teeth, to tear the flesh and to puncture the bones, and because the erect incisors, short canines and bicuspids were highly effective in securing a powerful hold upon the tough hide and connective tissue. It must be remembered that with a given muscular power small teeth are more easily forced into meat than large teeth.

After every feast there would be a residuum of hide and bones which would gradually assume economic value. The hides of animals were at first rudely stripped off simply to get at the meat. Small sharp-edged natural flints could be used for this purpose as well as to cut the sinews and flesh. After a time it was found that the furry sides of these hides were useful to cover the body at night or during a storm. Thus the initial stage in the making of clothes may have been a byproduct of the hunting habit.

Dr Matthew (loc. cit. pp. 211, 212) has well suggested that man may have learned to cover the body with the skins of animals in a cool temperate climate (such as that on the northern slopes of the Himalayas) and that afterward they were able to invade colder regions. The use of rough skins to cover the body must have caused exposure to new sources of annoyance and infection, but we cannot affirm that natural selection was the cause of the reduction of hair on the body and of the many correlated modifications of glandular activity. We can only affirm that a naked race of mammals must surely have had hairy ancestors and that the loss of hair on the body was probably subsequent to the adoption of predatory habits.

The food habits of the early HominidÆ, and thus indirectly the jaws and teeth, were later modified through the use of fire for softening the food. Men had early learned to huddle round the dying embers of forest fires that had been started by lightning, to feed the fire-monster with branches, and to carry about firebrands. They learned eventually that frozen meat could be softened by exposing it to the fire. Thus the broiling and roasting of meat and vegetables might be learned even before the ways of kindling fire through percussion and friction had been discovered. But the full art of cooking and the subsequent stages in the reduction of the jaws and teeth in the higher races probably had to await the development of vessels for holding hot water, perhaps in neolithic times.

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).

By the courtesy of the author we are permitted to reproduce his provisional diagram of the phylogeny of the HominidÆ and SimiidÆ (p. 337).