The human species

by A. de Quatrefages

But if I accept this doctrine as the only one reconcilable with facts, it is upon the condition of adopting it entirely, and as developed by studies upon the geographical distribution of all living beings. Now, works of this kind are numerous at the present time.

For all phanerogamous plants we have the work of M. Ad. de Candolle, which has been a standard work ever since its appearance.

Animals have not yet had their de Candolle. The great work of M. Alphonse Edwards will partly fill up this gap for the more southern regions of the globe. In the meantime, important investigations have been made in some of the principal classes. Buffon, by his admirable researches upon the geography of mammals, opened the way, in which he has been followed by the two Geoffroy Saint-Hilaires, Fr. Cuvier, and Andrew Murray; Dumeril and Bibron have studied reptiles from the same point of view; Fabricius, Latreille, Macley, Spence, Kirby, and Lacordaire have done the same for insects; M. Milne Edwards has worked out the distribution of the crustacea; I have endeavoured to do as much for the annelids. Finally, a great number of works bearing upon the lower groups have long been known to science, and Agassiz himself has largely contributed to increase our knowledge in this direction.

A certain number of general facts stand out from this mass of research, which we call laws. If the theory of Agassiz is true, it ought to agree with these laws. Now the disagreement is apparent from the outset.

Let us prove, in the first place, that this theory includes two very distinct ideas: that of the original cosmopolitanism of the human species; and, secondly, that of a geographical connection between the human race and the animal or vegetable groups observed in a common centre. Let us examine the truth and error contained in this last statement.

Agassiz holds that the influence of the centre of appearance is general and absolute. It extends to all the products of the soil as well as to those of fresh and salt waters. A country is just as much characterised by its plants and animals as by its human beings. In his opinion, an essentially local force seems to have produced all beings, or at least to have imprinted upon them a common mark.

This generalisation was inevitable. Any one who wishes to attach a human race to each centre of appearance is compelled to localise in each one of them the original cause of all the animal and vegetable forms which are indigenous in it. For all living beings geographical coincidence must be absolute.

Now there is generally no such coincidence. From the waters of a river to the banks which enclose it, the contrast may be striking. This is exactly what was shown by the discoveries of Agassiz himself in the ichthyology of the Amazon. To anyone who accepts the results published by the illustrious traveller, it is evident that this fauna may be divided into groups much more narrowly confined than those of terrestrial fauna. The same fact may be observed upon the shores of two seas separated by even a very narrow strip of land. The terrestrial fauna and flora are the same throughout the whole extent of the isthmus of Suez, whilst M. Edwards has not found a single species of crustacea common to both the Mediterranean and the Red Sea, and the study of annelids has led me to the same result.

Moreover, the same region may be the centre of appearance for one class of animals, but by no means for another. Australia, for example, is one of the most characteristic centres for mammals, and stands alone from this point of view among the surrounding countries. With respect to insects Australia agrees, on the contrary, with New Zealand, New Caledonia and the neighbouring islands. I have borrowed this last fact from Lacordaire. It has the more value since this entomologist has multiplied the centres of appearance to a much greater extent than Agassiz, and has, therefore, made their characterisation easier.

Thus the coincidence admitted by Agassiz, far from extending to all the organised beings of a region, does not even exist in certain cases between the different classes of animals alone.