that this was an ancestor of man, it is necessary to find now an ancestor to this Pithecanthropus, and it seems requisite that this ancestor be not inferior to existing anthropoids. It must have been capable of adopting, in case of need, the upright position, and been led, by its conformation, to take that attitude rather than the quadruped attitude. Such would be certainly the case with all known anthropoids, all of which are veritable biped climbers.
Let us recall here the existence in the Miocene epoch of several anthropoid species such as the Dryopithecus, the Pliopithecus, and the Anthropopithecus sivalensis. As Mr. Dubois has remarked, his species does not lack for ancestry.
The transformation of the habitual mode of locomotion may have been very rapid, but the consecutive, morphologic transformations must have demanded much time and cannot have been fixed hereditarily until after a certain number of generations—hundreds perhaps, and perhaps many less, for selection under the conditions indicated above may have been very active; the two sexes must have contributed actively to the progression, and the young must have imitated their parents with an ever-increasing facility. As regards the direct morphologic consequences of the change of attitude, we may suppose they were produced with great rapidity, if we are to judge from the multiple skeletal variations caused in man under the influence of the minimum of functional variations compared with those with which we have to do here.
As regards cerebral increase, it proceeds with such slowness that we can scarcely affirm the fact has been established at all for our European races since prehistoric times. But the cranial capacity of the Pithecanthropus surpassed by about 300 grams that of the largest gorillas. It surpassed by at least as much that of its ancestor gibbon z, if this latter was of the same stature as the Pithecanthropus. There is here an enormous difference, greater than that between the average for our lowest and the average for our highest existing human races. It is not, however, embarrassing for the hypothesis under discussion.
We must consider, in fact, that the human species has never realized, since the beginning of its existence, a progress comparable to that represented by the passage from the state of climber to the state of "marcheur bipède." This passage represents a veritable liberation of the superior members, the hands, previously employed as organs of locomotion the same as the feet. It is by the mode of locomotion of the climber that the hand became, little by little, apt for the function of prehension, then for the function of manipulation, and it is by virtue of the complete emancipation here supposed of the
