But to this all-essential germ, as thus given, I doubt not that the soil of such associations as the interjectional theory has in view must have been of no small importance; for this would naturally help to nourish its semiotic nature. And the reason why the similar germ of sign-making which occurs in the brute creation has not been similarly nurtured, I have already considered in Chapter VIII. For, it is needless to add, on every ground I disagree with the above quotations where they represent articulate sounds as having been aboriginally uttered by “Urmenschen” in the way of instinctive cries, without any vestige of semiotic intention.[304] * * * * * I will now pass on to consider the two other hypotheses; and by way of introduction to both we must remember that our materials of study on the side of the apes is very limited. I do not mean only that no single representative of any of the anthropoid apes has ever been made the object of even so much observation with respect to its intelligence as I bestowed upon a cebus. Yet this, no doubt, is an important point, because we know that of all quadrumana—and, therefore, of all existing animals—the anthropoid apes are the most intelligent, and, therefore, if specially trained would probably display greater aptitude in the matter of sign-making than is to be met with in any other kind of brute. But I do not press this point. What I now refer to is the fact that the existing species of anthropoid apes are very few in number, and appear to be all on the high-road to extinction. Moreover, it is certain that none of these existing species can have been the progenitor of man; and, lastly, it is equally certain that the extinct species (or genus) which did give origin to man must have differed in several important respects from any of its existing allies. In the first place, it must have been more social in habits; and, in the next place, it was probably more vociferous than the orang, the gorilla, or the chimpanzee. That there is no improbability in either of these suppositions will be at once apparent if we remember that both are amply sustained by analogies among existing and allied species of the monkey tribe. Or, to state these preliminary considerations in a converse form, when it is assumed[305] that because the few existing and expiring species of anthropoid apes are unsocial and comparatively silent, therefore the simian ancestors of man must have been so, it is enough to point to the variability of both these habits among certain allied genera of monkeys and baboons, in order at the same time to dispose of the assumption, and to indicate the probable reasons why one genus of ape gradually became evolved into _Homo_, while all the allied genera became, or are still becoming, extinct.