Page:The American Journal of Science, series 4, volume 4.djvu/253

Rh but of a transformation of the attitude even, that is to say of morphologic conditions entailing a radical change of type and, indirectly, of physio-psychologic modifications very profound.

The existence of a hiatus between two related living species cannot then serve as argument against the theory of evolution. This hiatus, as we have just seen, may be, on the contrary, a direct result of the transformation of one species into another.

Although the transformation here supposed has been very profound, enough so to give birth to a pretended new kingdom, "human kingdom," that transformation could have been produced, according to the above hypothesis, without compelling Nature to make, in any sense, a leap. It may be possible, from a point of view purely zoötaxic, to establish a veritable saltus, but I have just shown that this saltus could have been the gradual consequence of a simple modification of habits of locomotion in a race of monkeys already capable of assuming the upright position. The motive for this change could have arisen abruptly, but there has been no anatomic leap from Gibbon z to existing man. That which can have been produced abruptly is the exterior condition from which would have resulted, for an anthropoid race of climbers, the necessity of adopting habitually a mode of locomotion which it was already capable of utilizing occasionally. The only thing abrupt, from a biologic point of view, would have been a simple increase in the frequency of the utilization of a functional aptitude already existing. Multiple and considerable anatomic modification may have been entailed by this change of the habitual attitude, but they ought to have been produced by insensible degrees and are all the less astonishing in that the anthropoids already approach much nearer to man than to monkeys proper in their general conformation (Huxley, Broca).

If there is a gap between the existing human species and the precursor, the fossil remains of the intermediate races ought none the less to exist. There ought to be the remains of H0, of gibbon z and of Prothylobates. Will these last perhaps reveal a species remarkable in stature and in a relatively superior aptitude for the upright position? That is not necessary theoretically: the diverse species of the genus Hylobates have a conformation which enables them to assume the upright position with ease; the form may have undergone considerable variations after the transformation of the attitude.

Finally, it is probable that the species gibbon z approached man in certain respects more than do known species of the genus Hylobates.

However, if we admit that the pieces found at Trinil really represent the remains of a Pithecanthropus, and if it is admitted