Johann Friedrich Blumenbach is often criticised for his racial classification and supposed racism, but in this work, published in 1775, he not only argues for the unity of the human species, but in other passages for their general equality of intelligence, contrary to the use his ideas were later put to.
And now we must come more closely to the principal argument of our dissertation, which is concerned with this question; Are men, and have the men of all times and of every race been of one and the same, or clearly of more than one species? A question much discussed in these days, but so far as I know, seldom expressly treated of.
Ill-feeling, negligence, and the love of novelty have induced persons to take up the latter opinion. The idea of the plurality of human species has found particular favour with those who made it their business to throw doubt on the accuracy of Scripture. For on the first discovery of the Ethiopians, or the beardless inhabitants of America, it was much easier to pronounce them different species than to inquire into the structure of the human body, to consult the numerous anatomical authors and travellers, and carefully to weigh their good faith or carelessness, to compare parallel examples from the universal circuit of natural history, and then at last to come to an opinion, and investigate the causes of the variety. For such is the subtlety of the human intellect, and such the rush for novelty, that many would rather accept a new, though insufficiently considered opinion, than subscribe to ancient truths which have been commonly accepted for thousands of years.
I have endeavoured to keep free of all these mistakes; I have written this book quite unprejudiced, and I have desired nothing so much as that the arguments which I have brought forward for the unity of the human species, and for its mere varieties, may seem as satisfactory to my learned and candid readers as they do to myself.
For although there seems to be so great a difference between widely separate nations, that you might easily take the inhabitants of the Cape of Good Hope, the Greenlanders, and the Circassians for so many different species of man, yet when the matter is thoroughly considered, you see that all do so run into one another, and that one variety of mankind does so sensibly pass into the other, that you cannot mark out the limits between them. [Blumenbach, De Generis Humani Varietate Nativa, 1775 (On the natural varieties of mankind, English 1865)]
In order to make out this claim, Blumenbach also had to define what he meant by "species" in zoology. Despite his ascribing views to John Ray, it looks to me as if this is the first case in which someone explicitly states that "fecundity", i.e., interfertility, is a test of species. In other words, Blumenbach's is the first "biological" species discussion. In the third edition (1795), section 2, he writes:
23. What is species? We say that animals belong to one and the same species, if they agree so well in form and constitution, that those things in which they do differ may have arisen from degeneration. We say that those, on the other hand, are of different species, whose essential difference is such as cannot be explained by the known sources of degeneration, if I may be allowed to use such a word. So far well in the abstract, as they say. Now we come to the real difficulty, which is to set forth the characters by which, in the natural world, we may distinguish mere varieties from genuine species.
The immortal Ray, in the last century, long before Buffon, thought those animals should be referred to the same species, which copulate together, and have a fertile progeny. But, as in the domestic animals which man has subdued, this character seemed ambiguous and uncertain, on account of the enslaved life they lead; in the beginning of this century, the sagacious Frisch restricted it to wild animals alone, and declared that those were of the same species, who copulate in a natural state.1
But it must be confessed that, even with this limitation, we make but little progress. For, in the first place, what very little chance is there of bringing so many wild animals, especially the exotic ones, about which it is of the greatest possible interest for us to know whether they are to be considered as mere varieties, or as different species, to that test of copulation? especially if their native countries are widely apart; as is the case with the Satyrus Angolensis (Chimpanzee) and that of the island of Borneo (Orang-utan).
Then it is universally the case that the obscurity and doubt is much smaller, and of much less importance, in the case of wild animals on the point in question, than of those very animals which are excluded by this argument, that is, the domestic. Here, in truth, is the great difficulty. Hence the wonderful differences of opinion about, for example, the common dog, whose races you see are by some referred to many primitive species; by others are considered as mere degenerated varieties from that stock which is called the domestic dog (Chien de herger); again, there are others who think that all these varieties are derived from the jackal; and, finally, others contend that the latter, together with all the domestic dogs and their varieties, are descended from the wolf, and so forth.
As then the principle sought to be deduced from copulation is not sufficient to define the idea of species and its difference from variety, so neither are the other things which are adduced with this object, for example, the constancy of any character. Thus the snowy colour and the red pupils of the white variety of rabbit are as constant as any specific character could possibly be. So that I almost despair of being able to deduce any notion of species in the study of zoology, except from analogy and resemblance.
1 "When beasts by nature copulate with each other, it is an unfailing sign that they are of the same species." Berthout van Berchem fil. has lately adopted the same test of species, "if animals mix when in a natural state." But he makes no mention of Frisch, or even of Ray, nay, he says, "M. de Buffon, who was the first to abandon the little-to-be-depended-upon distinctions of the nomenclators, was also the first to make it understood that copulation was the best criterion for ascertaining species." See Mem. de la Sociéte des Sciences Physiques de Laitsanne, T. II. p. 49.
John wondered who coined the name Satyrus Angolensis?
Was thinking of Edward Tyson's wonderful and early comparative anatomy of the chimpanzee which he termed an orang-utan in his pleasingly titled.
"Orang-outang, sive, Homo sylvestris, or, The anatomy of a pygmie compared with that of a monkey, an ape, and a man: to which is added, A philological essay concerning the pygmies, the cynocephali, the satyrs and sphinges of the ancients : wherein it will appear that they are all either apes or monkeys, and not men, as formerly pretended"
He notes "Our Pygmie is no man , nor yet the Common Ape; but a sort of animal between both".