Certain families of languages do not differ solely by their constitution, they show special phonetic or physiological qualities;[205] that is to say, we can observe, in two different languages, varieties of the same order which is explained among animals, by the words barking, braying, cooing, etc. This is particularly the case with the strange language spoken by the clear-complexioned race of South Africa, probably much more widely diffused in former times than at present. It resembles no other known language, and consists in a _clucking_ which has, they say, nothing analogous to it among any other nation on the earth. The English have characterised it by the names of _sighing_, or _clucking_, and also especially _click language_.[206] Here is a new difference,--a radical difference in relation to so many others, which decidedly forms, from these Bosjesmans, a people whom it is impossible to ally, it does not signify how, or under what aspect, to any other of the divisions of the great human family. CHAPTER VI. THE INFLUENCE OF CLIMATE. Monogenists--starting from unity of origin as a fact, if not proved, at least accepted and unquestionable,--were necessarily led to discover a physiological explanation of the profound differences which we find at the present day among mankind, and which would have led them, according to monogenists, from one extreme state to the other, or from a medium state to the two extremes. Now, it is necessary to remember that every question concerning influence implies a previous historic notion. We cannot establish that a modification is not produced in a body (here is humanity), except by comparing it with itself at two distinct moments of duration, more or less distant. When a monogenist admits as an origin one uniform human race, he places a term of comparison in the past, he gives an historical date more or less definite to this uniform human species. And it is because religious cosmogonies alone dare, at the present day, to arrogate to themselves the power of making history dart back to the commencement of humanity, that we shall always be much troubled by not seeing a theological influence as the basis of monogenist ideas; now, they say, however, that they have discovered the trace of this human uniformity upon which they rely, in order to prove this great historical fact.