The cry of victory may be raised a little too soon. It may be hard to find the correct method, without being necessarily impossible. The “unitarians,” however, do not admit this reservation. They support their view by observing that certain tribes that belong to the same race show a very different physical type. They cite, for instance, the various branches of the hybrid Malayo-Polynesian family, without taking account of the proportion in which the elements are mingled in each case. If groups (they say) with a common origin can show quite a different conformation of features and skull, the unity of the human race cannot be disproved along these lines at all. However foreign the negro or Mongol type may appear to European eyes, this is no evidence of their different origin; the reasons why the human families have diverged will be found nearer to hand, and we may regard these physiological deviations merely as the result of certain local causes acting for a definite period of time.[[56]]

In face of so many objections, good and bad, the champions of multiplicity tried to extend the sphere of their arguments. Relying no longer on the mere study of skulls, they passed to that of the individual man as a whole. In order to prove (as is quite true) that the differences do not merely lie in the facial appearance and the bony conformation of the head, they brought forward other important differences with regard to the shape of the pelvis, the proportions of the limbs, the colour of the skin, and the nature of the capillary system.

Camper and other anthropologists had already recognized that the pelvis of the negro showed certain peculiarities. Dr. Vrolik pushed these inquiries further, and observed that the difference between the male and female pelvis was far less marked in the European, while in the negro race he saw in the pelvis of both sexes a considerable approximation to the brute. Assuming that the configuration of the pelvis necessarily affected that of the embryo, he inferred a difference of origin.[[57]]

Weber attacked this theory, with little result. He had to recognize that some formations of the pelvis were found in one race more frequently than in another; and all he could do was to show that there were some exceptions to Vrolik’s rule, and that certain American, African, and Mongolian specimens showed formations that were usually confined to Europeans. This does not prove very much, especially as, in speaking of these exceptions, Weber does not seem to have inquired whether the peculiar configuration in question might not result from a mixture of blood.

With regard to the size of the limbs, the opponents of a common origin assert that the European is better proportioned. The answer—which is a good one—is that we have no reason to be surprised at the thinness of the extremities in peoples who live mainly on vegetables or have not generally enough to eat. But as against the argument from the extraordinary development of the bust among the Quichuas, the critics who refuse to recognize this as a specific difference are on less firm ground. Their contention that the development among the mountaineers of Peru is explained by the height of the Andes, is hardly serious. There are many mountain-peoples in the world who are quite differently constituted from the Quichuas.[[58]]

The next point is the colour of the skin. The unitarians deny this any specific influence, first because the colour depends on facts of climate, and is not permanent—a very bold assertion; secondly because the colour is capable of infinite gradation, passing insensibly from white to yellow, from yellow to black, without showing a really definite line of cleavage. This proves nothing but the existence of a vast number of hybrids, a fact which the unitarians are continually neglecting, to the great prejudice of their theory.

As to the specific character of the hair, Flourens is of opinion that this is no argument against an original unity of race.

After this rapid review of the divergent theories I come to the great scientific stronghold of the unitarians, an argument of great weight, which I have kept to the end—I mean the ease with which the different branches of the human family create hybrids, and the fertility of these hybrids.

The observations of naturalists seem to prove that, in the animal or vegetable world, hybrids can be produced only from allied species, and that, even so, they are condemned to barrenness. It has also been observed that between related species intercourse, although possibly fertile, is repugnant, and usually has to be effected by trickery or force. This would tend to show that in the free state the number of hybrids is even more limited than when controlled by man. We may conclude that the power of producing fertile offspring is among the marks of a distinct species.

As nothing leads us to believe that the human race is outside this rule, there is no answer to this argument, which more than any other has served to hold in check the forces opposed to unity. We hear, it is true, that in certain parts of Oceania the native women who have become mothers by Europeans are no longer fitted for impregnation by their own kind. Assuming this to be true, we might make it the basis of a more profound inquiry; but, so far as the present discussion goes, we could not use it to weaken the general principle of the fertility of human hybrids and the infertility of all others; it has no bearing on any conclusions that may be drawn from this principle.