Then the earth is ever radiating away heat into space, the Professor reminds us. And so at last comes a vision of earthly cherubim, hopping heads, great unemotional intelligences, and little hearts, fighting together perforce and fiercely against the cold that grips them tighter and tighter. For the world is cooling—slowly and inevitably it grows colder as the years roll by. "We must imagine these creatures," says the Professor, "in galleries and laboratories deep down in the bowels of the earth. The whole world will be snow-covered and piled with ice; all animals, all vegetation vanished, except this last branch of the tree of life. The last men have gone even deeper, following the diminishing heat of the planet, and vast metallic shafts and ventilators make way for the air they need."
So with a glimpse of these human tadpoles, in their deep close gallery, with their boring machinery ringing away, and artificial lights glaring and casting black shadows, the Professor's horoscope concludes. Humanity in dismal retreat before the cold, changed beyond recognition. Yet the Professor is reasonable enough, his facts are current science, his methods orderly. The contemplative man shivers at the prospect, starts up to poke the fire, and the whole of this remarkable book that is not written vanishes straightway in the smoke of his pipe. This is the great advantage of this unwritten literature: there is no bother in changing the books. The contemplative man consoles himself for the destiny of the species with the lost portion of Kubla Khan.
THE EXTINCTION OF MAN
It is part of the excessive egotism of the human animal that the bare idea of its extinction seems incredible to it. "A world without us!" it says, as a heady young Cephalaspis might have said it in the old Silurian sea. But since the Cephalaspis and the Coccostëus many a fine animal has increased and multiplied upon the earth, lorded it over land or sea without a rival, and passed at last into the night. Surely it is not so unreasonable to ask why man should be an exception to the rule. From the scientific standpoint at least any reason for such exception is hard to find.
No doubt man is undisputed master at the present time—at least of most of the land surface; but so it has been before with other animals. Let us consider what light geology has to throw upon this. The great land and sea reptiles of the Mesozoic period, for instance, seem to have been as secure as humanity is now in their pre-eminence. But they passed away and left no descendants when the new orders of the mammals emerged from their obscurity. So, too, the huge Titanotheria of the American continent, and all the powerful mammals of Pleistocene South America, the sabre-toothed lion, for instance, and the Machrauchenia suddenly came to a finish when they were still almost at the zenith of their rule. And in no case does the record of the fossils show a really dominant species succeeded by its own descendants. What has usually happened in the past appears to be the emergence of some type of animal hitherto rare and unimportant, and the extinction, not simply of the previously ruling species, but of most of the forms that are at all closely related to it. Sometimes, indeed, as in the case of the extinct giants of South America, they vanished without any considerable rivals, victims of pestilence, famine, or, it may be, of that cumulative inefficiency that comes of a too undisputed life. So that the analogy of geology, at anyrate, is against this too acceptable view of man's certain tenure of the earth for the next few million years or so.
And, after all, even now man is by no means such a master of the kingdoms of life as he is apt to imagine. The sea, that mysterious nursery of living things, is for all practical purposes beyond his control. The low-water mark is his limit. Beyond that he may do a little with seine and dredge, murder a few million herrings a year as they come in to spawn, butcher his fellow air-breather, the whale, or haul now and then an unlucky king-crab or strange sea-urchin out of the deep water, in the name of science; but the life of the sea as a whole knows him not, plays out its slow drama of change and development unheeding him, and may in the end, in mere idle sport, throw up some new terrestrial denizens, some new competitor for space to live in and food to live upon, that will sweep him and all his little contrivances out of existence, as certainly and inevitably as he has swept away auk, bison, and dodo during the last two hundred years.
For instance, there are the Crustacea. As a group the crabs and lobsters are confined below the high-water mark. But experiments in air-breathing are no doubt in progress in this group—we already have tropical land-crabs—and as far as we know there is no reason why in the future these creatures should not increase in size and terrestrial capacity. In the past we have the evidence of the fossil Paradoxides that creatures of this kind may at least attain a length of six feet, and, considering their intense pugnacity, a crab of such dimensions would be as formidable a creature as one could well imagine. And their amphibious capacity would give them an advantage against us such as at present is only to be found in the case of the alligator or crocodile. If we imagine a shark that could raid out upon the land, or a tiger that could take refuge in the sea, we should have a fair suggestion of what a terrible monster a large predatory crab might prove. And so far as zoological science goes we must, at least, admit that such a creature is an evolutionary possibility.
Then, again, the order of the Cephalopods, to which belong the cuttle-fish and the octopus (sacred to Victor Hugo), may be, for all we can say to the contrary, an order with a future. Their kindred, the Gastropods, have, in the case of the snail and slug, learnt the trick of air-breathing. And not improbably there are even now genera of this order that have escaped the naturalist, or even well-known genera whose possibilities in growth and dietary are still unknown. Suppose some day a specimen of a new species is caught off the coast of Kent. It excites remark at a Royal Society soirée, engenders a Science Note or so, "A Huge Octopus!" and in the next year or so three or four other specimens come to hand, and the thing becomes familiar. "Probably a new and larger variety of Octopus so-and-so, hitherto supposed to be tropical," says Professor Gargoyle, and thinks he has disposed of it. Then conceive some mysterious boating accidents and deaths while bathing. A large animal of this kind coming into a region of frequent wrecks might so easily acquire a preferential taste for human nutriment, just as the Colorado beetle acquired a new taste for the common potato and gave up its old food-plants some years ago. Then perhaps a school or pack or flock of Octopus gigas would be found busy picking the sailors off a stranded ship, and then in the course of a few score years it might begin to stroll up the beaches and batten on excursionists. Soon it would be a common feature of the watering-places—possibly at last commoner than excursionists. Suppose such a creature were to appear—and it is, we repeat, a possibility, if perhaps a remote one—how could it be fought against? Something might be done by torpedoes; but, so far as our past knowledge goes, man has no means of seriously diminishing the numbers of any animal of the most rudimentary intelligence that made its fastness in the sea.