Part 19

Now these admitted facts about the Great Pyramid are surely remarkable, and worthy of the deepest consideration. They are facts which, in the pregnant words of the late Sir John Herschel, “according to received theories ought not to happen,” and which, he tells us, should therefore be kept ever present to our minds, since “they belong to the class of facts which serve as the clue to new discoveries.” According to modern theories, the higher civilisation is ever a growth and an outcome from a preceding lower state; and it is inferred that this progress is visible to us throughout all history and in all material records of human intellect. But here we have a building which marks the very dawn of history, which is the oldest authentic monument of man’s genius and skill, and which, instead of being far inferior, is very much superior to all which followed it. Great men are the products of their age and country, and the designer and constructors of this wonderful monument could never have arisen among an unintellectual and half-barbarous people. So perfect a work implies many preceding less perfect works which have disappeared. It marks the culminating point of an ancient civilisation, of the early stages of which we have no trace or record whatever.

The three cases to which I have now adverted (and there are many others) seem to require for their satisfactory interpretation a somewhat different view of human progress from that which is now generally accepted. Taken in connection with the great intellectual power of the ancient Greeks--which Mr. Galton believes to have been far above that of the average of any modern nation--and the elevation, at once intellectual and moral, displayed in the writings of Confucius, Zoroaster, and the Vedas, they point to the conclusion that, while in material progress there has been a tolerably steady advance, man’s intellectual and moral development reached almost its highest level in a very remote past. The lower, the more animal, but often the more energetic types have, however, always been far the more numerous; hence such established societies as have here and there arisen under the guidance of higher minds have always been liable to be swept away by the incursions of barbarians. Thus in almost every part of the globe there may have been a long succession of partial civilisations, each in turn succeeded by a period of barbarism; and this view seems supported by the occurrence of degraded types of skull along with such “as might have belonged to a philosopher,” at a time when the mammoth and the reindeer inhabited southern France.

Nor need we fear that there is not time enough for the rise and decay of so many successive civilisations as this view would imply; for the opinion is now gaining ground among geologists that palæolithic man was really preglacial, and that the great gap (marked alike by a change of physical conditions and of animal life) which in Europe always separates him from his neolithic successor, was caused by the coming on and passing away of the great ice age.

If the views now advanced are correct, many, perhaps most, of our existing savages are the successors of higher races; and their arts, often showing a wonderful similarity in distant continents, may have been derived from a common source among more civilised peoples.

Conclusion.--I must now conclude this very imperfect sketch of a few of the offshoots from the great tree of Biological study. It will, perhaps, be thought by some that my remarks have tended to the depreciation of our science, by hinting at imperfections in our knowledge and errors in our theories where more enthusiastic students see nothing but established truths. But I trust that I may have conveyed to many of my hearers a different impression. I have endeavoured to show that, even in what are usually considered the more trivial and superficial characters presented by natural objects, a whole field of new inquiry is opened up to us by the study of distribution and local conditions. And as regards man, I have endeavoured to fix your attention on a class of facts which indicate that the course of his development has been far less direct and simple than has hitherto been supposed; and that, instead of resembling a single tide with its advancing and receding ripples, it must rather be compared to the progress from neap to spring tides, both the rise and the depression being comparatively greater as the waters of true civilisation slowly advance towards the highest level they can reach.

And if we are thus led to believe that our present knowledge of nature is somewhat less complete than we have been accustomed to consider it, this is only what we might expect; for however great may have been the intellectual triumphs of the nineteenth century, we can hardly think so highly of its achievements as to imagine that, in somewhat less than twenty years, we have passed from complete ignorance to almost perfect knowledge on two such vast and complex subjects as the Origin of Species and the Antiquity of Man.

VIII.

THE DISTRIBUTION OF ANIMALS AS INDICATING GEOGRAPHICAL CHANGES.

Old Opinions on Continental Changes--Theory of Oceanic Islands--Present and Past Distribution of Land and Sea--Zoological Regions--The Palæarctic Region--The Ethiopian Region--The Oriental Region--Past Changes of the Great Eastern Continent--Regions of the New World--Past History of the American Continents--The Australian Region--Summary and Conclusion.

This is one of the Lectures on Scientific Geography delivered before the Royal Geographical Society, but the introductory portion has been rewritten. The original Lecture appeared in the Proceedings of the Society for September, 1877, under the title: “On the Comparative Antiquity of Continents, as indicated by the Distribution of Living and Extinct Animals.”

There is a curious old book entitled Restitution of Decayed Intelligence in Antiquities Concerning the Most Noble and Renowned English Nation, written in 1605, by R. Verstegen. The fourth chapter treats “Of the Isles of Albion, and how it is showed to have been continent or firm land with Gallia, now named France, since the Flood of Noe;” and after referring to several ancient writers who had held this opinion but without giving any reasons for it, the author proceeds to argue the point, referring to the narrowness of the straits, their extreme shallowness, the similarity of the opposite coasts both in height and character, the meaning of the word “cliff” as being that which is cleft asunder, and other matters; after which comes this quaint and interesting passage:--

“Another reason there is that this separation hath been made since the flood, which is also very considerable, and that is the patriarch Noe, having had with him in the Ark all sorts of beasts, these then, after the flood, being put forth of the ark to increase and multiply, did afterward in time disperse themselves over all parts of the continent or main land; but long after it could not be before the ravenous wolf had made his kind nature known to man, and therefore no man unless he were mad, would ever transport of that race out of the continent into the isles, no more than men will ever carry foxes (though they be less damageable) out of our continent into the Isle of Wight. But our Isle, as is aforesaid, continuing since the flood fastened by nature unto the Great Continent, those wicked beasts did of themselves pass over. And if any should object that England hath no wolves on it they may be answered that Scotland, being therewith conjoined, hath very many, and so England itself sometime also had, until such time as King Edgar took order for the destroying of these throughout the whole realm.”

The preservation of foxes for sporting purposes was evidently quite out of the range of thought at this not very distant epoch, and our author, in consequence, made a little mistake as to what men “ever” would do in the case of these noxious animals; but his general argument is sound, and it becomes much strengthened when we take into consideration the smaller vermin, such as stoats, weasels, moles, hedgehogs, fieldmice, vipers, toads, and newts, which would certainly not all have been brought over by uncivilised man, even if any one of them might have been. But there is another reason why they were not so brought over. For on that supposition we should discover remains of fewer and fewer species as we go back into past times till at last when we reached the time of the first occupation of the country by man we should find none at all. But the actual facts are the very reverse of this. For the further we go back the more species of noxious and dangerous animals we discover, till in the time of the palæolithic (or oldest) prehistoric men, we find remains not only of almost every animal now living, but of many others still less likely to have been introduced by man’s agency. Such are the mammoths, rhinoceroses, lions, horses, bears, gluttons, and many others; and it is equally impossible that these could all have swum across an arm of the sea, which although only about twenty miles wide in its narrowest past, is yet so influenced by strong tides and currents that it becomes as effective a barrier as many straits of double the width.

Owing, however, to the want of all definite ideas as to the mode by which the earth became stocked with animals and plants, the existence of identical species in countries separated by arms of the sea attracted very little attention till quite recent times. It is probable that Mr. Darwin was really the first person to see the full importance of the principle, for in his Naturalist’s Voyage Round the World, he remarks, that “the South American character of the West Indian mammals seems to indicate that this archipelago was formerly united to the southern continent.” Some years later, in 1845, Mr. George Windsor Earl called special attention to the subject by pointing out that the great Malay Archipelago may be divided in two portions, all the islands in the western half being united to each other and to the continent of Asia by a very shallow sea, and all having very similar productions, while many large animals, such as the elephant, rhinoceros, wild cattle, and tigers, range over most of them. We then come to a profoundly deep sea, and the islands of the eastern half of the archipelago are either surrounded by a deep sea or are connected by a shallow sea to Australia; and in this half the productions resemble those of Australia, marsupials being found in all the islands while the large quadrupeds of Asia are almost wholly unknown.

Theory of Oceanic Islands.--In 1859 the Origin of Species was published, and in the thirteenth chapter of this celebrated work Mr. Darwin put forth his views on oceanic islands or such as are situated far away from any continent and are surrounded by deep oceans. It had been up to this time believed that in most cases these islands were fragments of ancient continents; as an example of which we may refer to the Azores, Madeira, and the other Atlantic islands, which were thought to support the notion of an Atlantic or western extension of the European continent. In order to ascertain what was the condition of these islands when first discovered, Mr. Darwin searched through all the oldest voyages, and found that in none of them was a single native mammal known to exist, while in almost all of them frogs and toads were also absent. All the Atlantic isles from the Azores to St. Helena; Mauritius, Bourbon, and the other isles of the Indian Ocean; and the Pacific islands, east of the Fijis, as far as the Galapagos and Juan Fernandez are thus deficient. They all of them, however, possess birds, and most of them bats; and whenever small mammalia, such as goats, pigs, rabbits, and mice have been introduced they have run wild and often increased enormously, proving that the only reason why such animals were not originally found there was the impossibility of them crossing the sea; while such as could fly over--birds, bats, and insects--existed in greater or less abundance. If, on the other hand, they had once formed part of the continent, it is impossible to believe that some of the smaller mammalia, as well as frogs, would not have continued to exist in the islands to the present day.

If we compare the productions of different islands, we meet with peculiarities which throw much light on the subject of distribution. In the Galapagos islands, between 500 and 600 miles from the west coast of South America, there are thirty-two species of land-birds, all but two or three being peculiar to the group. In Madeira, about 400 miles from the coast of Morocco, there are nearly twice as many land-birds as in the Galapagos, but only two of these are peculiar to the island, the rest being South European or N. African species. The Azores are 1,000 miles west of Portugal, and they contain twenty-two species of land-birds, every one of which is European except one bullfinch which is slightly different and forms a peculiar species. This remarkable difference in the proportion of peculiar species between the Galapagos and the Atlantic islands, is well explained by the theory that land-birds rarely fly directly out to sea, except when carried against their will by storms and gales of wind. Now the Azores are situated in an especially stormy zone, and it is an observed fact that after every severe gale of wind some new bird or insect is seen on the islands. The Galapagos, on the contrary, are in a very calm sea where violent storms are almost unknown, and thus new birds from the mainland very rarely visit these islands. Madeira is less stormy than the Azores, but its comparative nearness makes up for this difference in the case of birds. In insects, however, the species of Madeira are much more peculiar (and more numerous) than those of the more distant Azores; while those of the Galapagos are few, but all peculiar, and belonging to groups many of which are widely spread over the globe. All these facts are entirely in accordance with the view that oceanic islands have been peopled from the nearest continents by various accidental causes; while they are entirely opposed to the theory that such islands are remnants of old continents and have preserved some portion of their inhabitants.

It is a curious fact, that land reptiles, such as snakes and lizards, are found in many islands where there are no mammalia or frogs; and we therefore conclude that there must be some means by which their ova can be safely carried across great widths of sea. A single peculiar frog inhabits New Zealand, and some species are found in the Pacific islands as far eastward as the Fijis, but they are absent from all other oceanic islands. Snakes also extend to the Fijis, and there are two species in the Galapagos, but none in the other oceanic islands. Lizards, however, are found in Mauritius and Bourbon; in New Zealand; in all the Pacific islands, and in the Galapagos. It is clear then that next to Mammals, frogs and toads are most completely shut out by an ocean barrier; then follow snakes, but as these are only found in the Galapagos and are very like South American species, they may possibly have been conveyed in boats or by floating trees. Lizards, however, are so wide-spread over almost all the warmer islands of the great oceans, that they must have some natural way of passing over, but the exact mode in which this is effected has not yet been discovered. Birds, as we have seen, are liable to be carried by winds and storms over great widths of sea, but this only applies to certain groups; and large numbers which feed on the ground or which inhabit the depths of the forests, are almost as strictly confined to their respective countries by even a narrow arm of the sea as are the majority of the mammalia.

This sketch of the mode in which the various kinds of islands have been stocked with their animal inhabitants forms the best introduction to the study of those changes in our continents which have led to the existing distribution of animals. It demonstrates the importance of the sea as a barrier to the spread of all the higher animals; and we are thus naturally led on to inquire, how far and to what extent such barriers have in past time existed between lands which are now united, and on the other hand what existing oceanic barriers are of comparatively recent origin. In pursuing this inquiry we shall have to take account of those grand views of the course of nature associated with the names of Lyell and Darwin--of the slow but never-ceasing changes in the physical conditions, the outlines and the mutual relations of the land-surfaces of the globe; and of the equally slow and equally unceasing changes in the forms and structures of all organisms, to a great extent correlated with, and perhaps dependent on, the former set of changes. Combining these two great principles with other ascertained causes of distribution, we shall be enabled to deal adequately with the problem before us, and give a rational, though often only an approximative and conjectural, solution of the many strange anomalies we meet with in studying the distribution of living things.

Past and Present Distribution of Land and Sea.--Before proceeding to give details as to the distribution of animals, it is necessary to point out certain geographical features which have had great influence in bringing about the existing state of things.

The extreme inequality with which land and water is distributed has often been remarked, but what is less frequently noted is the singular way in which all the great masses of land are linked together. Notwithstanding the small proportion of land to water, the vast difference in the quantity of land in the northern and southern hemispheres, and the apparently hap-hazard manner in which it is spread over the globe, we yet find that no important area is completely isolated from the rest. We may even travel from the extreme north of Asia to the three great southern promontories--Cape Horn, the Cape of Good Hope, and Tasmania--without ever going out of sight of land; and, if we examine a terrestrial globe, we find that the continents in their totality may be likened to a huge creeping plant, whose roots are at or around the North Pole, whose matted stems and branches cover a large part of the northern hemisphere, while it sends out in three directions great offshoots towards the South Pole. This singular arrangement of the land surface into what is practically one huge mass with diverging arms, offers great facilities for the transmission of the varied forms of animal life over the whole earth, and is no doubt one of the chief causes of the essential unity of type which everywhere characterises the existing animal and vegetable productions of the globe.

There is, moreover, good reason to believe that the general features of this arrangement are of vast antiquity; and that throughout much of the Tertiary period, at all events, the relative positions of our continents and oceans have remained the same, although they have certainly undergone some changes in their extent, and in the degree of their connection with each other. This is proved by two kinds of evidence. In the first place, it is now ascertained by actual measurement that the depths of the great oceans are so vast over wide areas, while the highest elevations of the land are limited to comparatively narrow ridges, that the mass of land (above the sea-level) is not more than ¹⁄₃₆th part of the mass of the ocean. Now we have reason to believe that subsidence and elevation bear some kind of proportion to each other, whence it follows that although several mountain ranges have risen to great heights during the Tertiary period, this amount of elevation bears no proportion to the amount of subsidence required to have changed any considerable area of what was once land into such profound depths as those of the Atlantic or Pacific Oceans. In the second place, we find over a considerable area of all the great continents fresh-water deposits containing the remains of land animals and plants; which deposits must have been formed in lakes or estuaries, and which therefore, speaking generally, imply the existence in their immediate vicinity of land areas comparable to those which still exist. The Miocene deposits of Central and Western Europe, of Greece, of India, and of China, as well as those of various parts of North America, strikingly prove this; while the Eocene deposits of London and Paris, of Belgium, and of various parts of North and South America, though often marine, yet by their abundant remains of land-animals and plants, equally indicate the vicinity of extensive continents. For our purpose it is not necessary to go further back than this, but there is much evidence to show that throughout the Secondary, and even some portion of the Palæozoic periods, the land-areas coincided to a considerable extent with our existing continents. Professor Ramsay has shown that not only the Wealden formation, and considerable portions of the Upper and Lower Oolite, but also much of the Trias, and the larger part of the Permian, Carboniferous, and Old Red Sandstone formations, were almost certainly deposited either in lakes, inland seas, or extensive estuaries. This would prove that, throughout the whole of the vast epochs extending back to the time of the Devonian formation, our present continents have been substantially in existence, subject, no doubt, to vast fluctuations by extension or contraction, and by various degrees of union or separation, but never so completely submerged as to be replaced by oceans comparable in depth with our Atlantic or Pacific.

Nature, 1873, p. 333; Quarterly Journal of the Geological Society, 1871, pp. 189 and 241.

This general conclusion is of great importance in the study of the geographical distribution of animals, because it bids us avoid the too hasty assumption that the countless anomalies we meet with are to be explained by great changes in the distribution of land and sea, and leads us to rely more on the inherent powers of dispersal which all organisms possess, and on the union or disruption, extension or diminution, of existing lands--but always in such directions and to such a limited extent as not to involve the elevation of what are now the profoundest depths of the great oceans.

Zoological Regions.--We will now proceed to sketch out the zoological features of the six great biological regions; and will afterwards discuss their probable changes during the more recent geographical periods, in accordance with the principles here laid down.

The Palæarctic Region.

The Palæarctic, or North Temperate region of the Old World, is not only by far the most extensive of the zoological regions, but is the one which agrees least with our ordinary geographical divisions. It includes the whole of Europe, by far the largest part of Asia, and a considerable tract of North Africa; yet over the whole of this vast area there prevails a unity of the forms of animal life which renders any primary subdivision of it impossible, and even secondary divisions difficult. But besides being the largest of the great zoological regions, there are good reasons for believing this to represent the most ancient, and therefore the most important centre of the development of the higher forms of animal life,--and it is therefore well to consider it first in order.

In enumerating the most important animal groups characteristic of this and other regions, it must be clearly understood that such groups are not always absolutely confined to one region. Here and there they will often overlap the boundaries, while in other cases single species may have a wide distribution in one or more of the adjacent regions; but this does not at all affect the main fact, that the group as a whole is very abundant and very widely spread over the region in question, while it is very rare, or confined to a very limited area in adjacent regions, and is therefore specially characteristic of the one as compared with other parts of the world. Bearing this in mind, we shall find that the Palæarctic region is well characterized by a considerable number of typical groups, although, as we shall presently see, it has in recent geological times lost much of its ancient richness and variety of animal life.

Among Mammalia the groups most characteristic of this region are the moles (Talpidæ), a family consisting of eight distinct genera which range over the whole region, but beyond it barely enter the Oriental region in North India, and the Nearctic region in North-West America; camels, confined to the deserts of North Africa and Asia; sheep and goats (Capra), only found beyond the region in the Nilgherries and Rocky Mountains; several groups of antelopes, and many peculiar forms of deer; hamsters (Cricetus), sand rats (Psammomys), mole rats (Spalax), and pikas (Lagomys), with several other forms of rodents. Wolves, foxes, and bears, are also very characteristic, though by no means confined to the region.