There were no human eyes to see nor human ears to hear what went on in southern California when it held an animal life as fierce and strange and formidable as mid-Africa to-day. The towering imperial elephants and the burly mastodons trumpeted their approach one to the other. The great camels, striding noiselessly on their padded feet, passed the clumsy ground-sloths on their way to water. The herds of huge horses and bison drank together in pools where the edges were trodden into mire by innumerable hoofs. All these creatures grew alertly on guard when the shadows lengthened and the long-drawn baying of the wolf pack heralded the night of slaughter and of fear; and the dusk thrilled with the ominous questing yawns of sabretooth and giant tiger, as the beasts of havoc prowled abroad from their day lairs among the manzanitas, or under cypress and live-oak.
The tar-pools caught birds as well as beasts. Most of these birds were modern—vultures, eagles, geese, herons. But there were condor-like birds twice the size of any living condor, the biggest birds, so far as we know, that ever flew. There were also, instead of wild turkeys, great quantities of wild peacocks—at least they have been identified as peacocks or similar big, pheasant-like birds. If the identification is correct, this is an unexpected discovery and a fresh proof of how this extinct American fauna at so many points resembled that of Asia. It was natural that a collateral ancestor of the present Asiatic pheasant-like birds should dwell beside a collateral ancestor of the present Asiatic tiger.[1]
Moreover, the tar-pools hold human bones. These, however, are probably of much later date than the magnificent fauna above described, perhaps only a few thousand years old. They belong to a rather advanced type of man. It is probable that before man came to America at all, the earlier types had died out in Eurasia, or had been absorbed and developed, or else had been thrust southward into Africa, Tasmania, Australia, and remote forest tracts of Indo-Malaysia, where, being such backward savages, they never developed anything remotely resembling a civilization. It was probably people kin to some of the later cave-dwellers who furnished the first (and perhaps until the advent of the white man the only important) immigration to America. These immigrants, the ancestors of all the tribes of Indians, spread from Alaska to [Tierra] del Fuego. Over most of the territory in both Americas they remained at the hunting stage of savage life, although they generally supplemented their hunting by a certain amount of cultivation of the soil, and although in places they developed into advanced and very peculiar culture communities.
When these savages reached North America it is likely, from our present knowledge, that the terrible and magnificent Pleistocene fauna had vanished, although in places the last survivors of the mastodon, and perhaps of one or two other forms, may still have lingered. What were the causes of this wide-spread, and complete, and—geologically speaking—sudden extermination of so many and so varied types of great herbivorous creatures, we cannot say. It may be we can never do more than guess at them. It is certainly an extraordinary thing that complete destruction should have suddenly fallen on all, literally all, of the species. Camels and horses, after they had dwelt on this continent for millions of years, since almost the dawn of mammalian life, developing from little beasts the size of woodchucks into the largest and most stately creatures of their kind that ever trod the earth's surface, all at once disappeared to the very last individual. Ground-sloths and elephants vanished likewise. The bigger forms of bison also died out, although one species remained. Many causes of extinction have been suggested. Perhaps all of them were more or less operative. Perhaps others of which we know nothing were operative. We cannot say.
But as regards certain of the formidable, but heavy rather than active, beasts of prey it is possible to hazard a guess. Compared to agile destroyers like the cougar and the timber-wolf, the sabretooth and the big-headed, small-legged giant wolf were strong, heavy, rather clumsy creatures. Predatory animals of their kind were beasts of battle rather than beasts of the chase. They were fitted to overcome by downright fighting strength a big, slow, self-confident quarry, rather than to run down a swift and timid quarry by speed or creep up to a wary and timid quarry by sinuous stealth. So long as the heavy herbivores were the most numerous these fighting carnivores were dominant over their sly, swift, slinking brethren. But when the great mass of plant-eaters grew to trust to speed and vigilance for their safety there was no longer room for preying beasts of mere prowess.
In South America it is probable that the heavy fauna died out much later than in North America and northern Eurasia; that is, it died out much later than in what zoogeographers call the holarctic realm. During most of the Tertiary period or age of mammals, the period intervening between the close of the age of great reptiles and the time when man in human form appeared on the planet, South America was an island, and its faunal history was as distinct and peculiar as that of Australia. Aside from marsupials and New World monkeys, its most characteristic animals were edentates and very queer ungulates with no resemblance to those of any other continent. Toward the close of the Tertiary land bridges connected the two Americas, and an interchange of faunas followed. The South American fauna was immensely enriched by the incoming of elephants, horses, sabretooth cats, true cats, camels, bears, tapirs, peccaries, deer, and dogs, all of which developed along new and individual lines. A few of these species, llamas and tapirs for instance, still persist in South America although they have died out in the land from which they came. But in the end, and also for unknown causes, this great fauna died out in South America likewise, leaving a continent faunistically even more impoverished than North America. The great autochthonous forms shared the extinction of the big creatures of the immigrant fauna; for under stress of competition with the newcomers, the ancient ungulates and edentates had developed giants of their own.
Recent discoveries have shown that the extinction was not complete when the ancestors of the Indians of to-day reached the southern Andes and the Argentine plains. An age previously the forefathers of these newcomers had lived in a land with the wild horse, the wild elephant, and the lion; and now, at the opposite end of the world, they had themselves reached such a land. The elephants were mastodons of peculiar type; the horses were of several kinds, some resembling modern horses, others differing from them in leg and skull formation more than any of the existing species of ass, horse, or zebra differ from one another; the huge cats probably resembled some other big modern feline more than they did the lion. Associated with them were many great beasts, whose like does not now exist on earth. The sabretooth was there, as formidable as his brother of the north, and, like this brother, bigger and more specialized than any of his Old World kin, which were probably already extinct. Among the ungulates of native origin was the long-necked, high-standing macrauchenia, shaped something like a huge, humpless camel or giraffe, and with a short proboscis. This animal doubtless browsed among the trees. Another native ungulate, the toxodon, as big and heavily made as a rhinoceros, was probably amphibious, and had teeth superficially resembling those of a rodent. The edentates not only included various ground-sloths, among them the megatherium, which was the size of an elephant, and the somewhat smaller mylodon, but also creatures as fantastic as those of a nightmare. These were the glyptodons, which were bulkier than oxen and were clad in defensive plate-armor more complete than that of an armadillo; in one species the long, armored tail terminated in a huge spiked knob, like that of some forms of mediæval mace.
The glyptodons doubtless trusted for protection to their mailed coats. The ground-sloths had no armor. Like the terrestrial ant-bear of Brazil they walked slowly on the outer edges of their fore feet, which were armed with long and powerful digging claws. They could neither flee nor hide; and it seems a marvel that they could have held their own in the land against the big cats and sabretooth. Yet they persisted for ages, and spread northward from South America. It is hard to account for this. But it is just as hard to account for certain phenomena that are occurring before our very eyes. While journeying through the interior of Brazil I not infrequently came across the big tamandua, the ant-bear or ant-eater. We found it not only in the forests but out on the marshes and prairies. It is almost as big as a small black bear. In its native haunts it is very conspicuous, both because of its size and its coloration, and as it never attempts to hide it is always easily seen. It is so slow that a man can run it down on foot. It has no teeth, and its long, curved snout gives its small head an almost bird-like look. Its fore paws, armed with long, digging claws, are turned in, and it walks on their sides. It is long-haired and thick-hided, colored black and white, and with a long, bushy tail held aloft; and as it retreats at a wabbly canter, its brush shaking above its back, it looks anything but formidable. Yet it is a gallant fighter, and can inflict severe wounds with its claws, as well as hugging with its powerful fore legs; and if menaced it will itself fearlessly assail man or dog. When chased by hounds, in the open, I have seen one instantly throw itself on its back, in which position it was much more dangerous to the hounds than they were to it. Doubtless if attacked by a jaguar—and we killed jaguars in the immediate neighborhood—it would, if given a moment's warning, have defended itself in the same fashion. I suppose that this defense would be successful; for otherwise it seems incredible that such a conspicuous, slow-moving beast can exist at all in exactly the places where jaguars, able to kill a cow or horse, are plentiful. But, even so, it is difficult to understand how it has been able to persist for ages in company with the great spotted cat, the tyrant of the Brazilian wilderness. At any rate, with this example before us, we need not wonder overmuch at the ability of megatherium and mylodon to hold their own in the presence of the sabretooth.
In the late fall of 1913, as previously [described], I motored north from the beautiful Andean lake, Nahuel Huapi, through the stony Patagonian plains to the Rio Negro. The only wild things of any size that we saw were the rheas, or South American ostriches, and a couple of guanacos, or wild llamas, small, swift, humpless camels, of which the ancestral forms were abundant in the North American Miocene. But one of my companions, the distinguished Argentine explorer, educator, and man of science, Francisco Moreno, had some years previously made a discovery which showed that not many thousand years back, when the Indians had already come into the land, the huge and varied fauna of the Pleistocene still lingered at the foot of the Andes. He had found a cave in which savage men had dwelt; and in the cave were the remains of the animals which they had killed, or which had entered the cave at times when its human tenants were absent. Besides the weapons and utensils of the savages, he had found the grass which they had used for beds, and enclosures walled with stones for purposes of which he could not be sure. It will be remembered that in the cave-home of the 'Ndorobo which Kermit found there were beds of grass, and enclosures walled with brush, in which their dogs were kept. Whether these early Patagonian Indians had dogs I do not know; but many African tribes build low stone walls as foundations for sheds used for different purposes; and sometimes, among savages, it is absolutely impossible to guess the use to which a given structure is put unless it is actually seen in use—exactly as sometimes it is wholly impossible to divine what a particular specimen of savage pictorial art indicates unless the savage is there to explain it to his civilized brother.
Among the signs of human occupation Doctor Moreno found, well preserved in the cold cave, not only the almost fresh bones, but even pieces of the skin, of certain extinct animals. Among the species whose bones were found were the macrauchenia, tiger, horse, and mylodon. When Doctor Moreno said tiger, I asked if he did not mean jaguar; but he said no, that he meant a huge cat like an Old World lion or tiger; I do not know with what modern feline its affinities were closest. The discovery of the comparatively fresh remains of the horse gave rise in some quarters to the belief that it was possible this species of horse survived to the day the Spaniards came to the Argentine and was partly ancestral to the modern Argentine horse; but the supposition is untenable, for the horse in question represents a very archaic and peculiar type, with specialized legs and an extraordinary skull, and could not possibly have had anything to do with the production of the wild, or rather feral, horses of the pampas and the Patagonian plains. Of the mylodon Doctor Moreno found not only comparatively fresh bones, with bits of sinew, but dried dung—almost as large as that of an elephant—and some big pieces of skin. The skin was clothed with long, coarse hair, and small ossicles were set into it, making minute bony plates. Doctor Moreno gave me a fragment of the skin, and also bones and dung; they are now in the American Museum of Natural History. The discovery gave rise to much fanciful conjecture; it was even said that the mylodon had been domesticated and kept tame in the caves; but Doctor Moreno laughed at the supposition and said that it lacked any foundation in fact. He also said that, contrary to what has sometimes been asserted, the age of the remains must be estimated in thousands, possibly ten thousands, and certainly not hundreds, of years.