Consequently, however great the differences existing between these human groups may be, or may appear to be, to consider them as specific characters is a perfectly arbitrary estimation of their value. It is, to say the least, quite as rational, quite as scientific, to consider these differences only as characters of race, and even on that account to refer all the human groups to a single species.
The legitimacy of this conclusion is incontestable. Now, I repeat, that this conclusion is sufficient to destroy the very foundation of the polygenistic theory. In reality this theory rests entirely upon morphological considerations. Its partisans, struck only by the material differences presented by the human groups, have thought it impossible to account for them, except by the admission of the existence of several species. By showing that facts of this nature can be equally well interpreted under the hypothesis of the Unity of the Species, monogenism and polygenism are, so to speak, placed on an equal footing.
CHAPTER VI.
INTERCROSSING AND FUSION OF CHARACTERS IN ANIMAL RACES; APPLICATION TO MAN.
Without even quitting the ground of morphology, it will be easy to prove which theory is most probably the correct one.
We know that naturalists consider that all individuals which pass from one to another by invisible shades belong to the same species, however different the extremes may be. All great museums contain examples of this fact.
The grounds for this conclusion are much stronger when there exists an intercrossing of characters. This intercrossing exists when a very decided and apparently exclusive character reappears in one or several individuals differing widely in other respects, and undoubtedly belonging to distinct groups. It is a case of intercrossing again, when the same character varies in such a manner as to lead, if considered apart, to the division of a natural group, and to the separation of the fractions into very different groups.
Now there is no animal species which presents these essentially morphological characters in a higher degree than man. When the human groups are studied in some detail, the difficulty does not consist in finding resemblances, but in clearly defining the differences. The more carefully they are considered, the more they disappear and become obliterated. We then understand the accounts given by most trustworthy travellers, such as d’Abbadie, of countries where the Negro and the White live side by side. In their extremes these two types are certainly very distinct. But in Abyssinia, for example, where they have long lived in contact, and intermingled, the Negro is no longer characterised by either colour, features, or hair, but simply by the exaggerated protuberance of the heel. This character in its turn, however, loses its value on the Eastern coast of Africa, where whole Negro tribes have the heel formed like ours.
This is an example of intercrossing, and they could easily be multiplied. I have already observed how closely the Aryan or Dravidian Hindoos, African or Melanesian Negroes and manifestly Semitic populations may resemble each other in colour. The following is a still more striking example. Desmoulins regarded the perforation of the olecranon process as one of the most decided characters of his Austro-African species of man. Now this perforation reappears in Egyptian and Guanche mummies, in a large number of European skeletons of the neolithic period, the crania of which moreover, exhibit no other relations with those of the Bosjesmans, and even in some Europeans of the present epoch.
The intercrossing of characters between human groups becomes still more evident from the comparison of numerical data taken from a number of different groups. I shall confine myself for the moment to giving the results arrived at by the study of the stature when the representative numbers are placed in order. We shall presently meet with other examples.