with digitate feathers, the hind legs were wide apart and far back, with distinct tibia and fibula as in the reptiles, with the three pelvic bones distinct as in reptiles with no body feathers, the latter on only the wings, legs and tails-with feeble flight and obvious volplaning habits. (Archæopteryx or lizard tailed bird of the upper Jurassic.) Before taking up man, I have time to consider but two among the many groups of mammals whose history is almost completely known. You doubtless think of elephants in North America only in connection with zoological gardens or circuses, and yet the elephants were a most conspicuous element of the American fauna from the middle Miocene to the end of the Pleistocene, and numerous bones and teeth have been found here in Maryland. They lived in America much longer than has the human race and much longer than the bears which we commonly think of as characteristically American. The elephants were originally immigrants from the old world. They occupy to-day a somewhat isolated position among hoofed mammals and display a curious but readily understandable mixture of specialized and primitive characters. Their specializations are in head and teeth, their conservatism is in body and limbs. To understand their ancestry, we must understand the five or six African and Asian species of the present. Their most obvious feature is the long trunk or proboscis that gives the name Proboscidia to the order. This trunk is simply an elongated nose, although it did not come into existence in the way Kipling relates. Aside from the trunk the tusks mark the elephant. These are simply much modified upper incisor teeth. The dental formula is 1 0 0 3 then i c pm m- This is not the whole story of the teeth, 0 0 0 3 however, for, if you examine an elephant's teeth, you will rarely find more than a single immense functional grinder in each jaw ramus the milk molars, developing serially 1, 2, 3, and followed in turn by the molars 1, 2, 3 during life-the worn ones being pushed forward and out, a contrivance for increasing the elephant's life span, for an animal is only as long lived as its teeth. The mechanics of trunk and tusk support have specialized the head; cranial bones are thickened and lightened, hence the difficulty of shooting an elephant in the brain. The neck is shortened to bring the head weight nearer the withers. The body is long and massive with large shoulder and hip bones. The feet are short and broad with the nail-like hoofs around the edge. Toes are five but not all hoofed (Indian 5 in front, 4 behind; East African 4 in front, 3 behind). Limb adaptations are those common to all heavy animals of other stocks. Most quadrupeds have knee and elbow per manently bent. Great weight necessitates the straightening of the limb and individual bones and the shifting of the articular surfaces from an oblique to a right angled position. Weight of tusks causes a shortening and heightening of the skull. Shortening brings the weight arm of the lever nearer the fulcrum at the neck, and heightening lengthens the power arm and affords attachment for the increased musculature. (Modern tusks weighing 239 lbs. each are recorded.) The lengthening of the trunk makes it unnecessary for the mouth to reach the ground for food and water. The earliest known fossil elephant, only a potential elephant, was of upper Eocene age and comes from near Lake Moeris in the Fayûm, and was consequently christened Moeritherium. It was small and somewhat suggestive of a tapir. The skull was long and narrow, the trunk was merely a snout, the neck was moderately long and the limbs were slender. The teeth were the most signi small and simple, the second was a downwardly directed small tusk. The third and the canine were non-functional and there were 6 grinders, simple and quadritubercular (4 cusps and 2 crests). In the lower jaw the incisors were procumbent. The first long, the second an enamelled tusk with worn chisel edge; the third and canine already gone and 6 grinders. The second stage of elephant evolution was Palæomastodon of the lower Oligocene of the same region. Several species are known, ranging in size from that of a modern tapir to a half grown Indian elephant. 1 0 3 3 Tooth formula i co pm m3 canines have gone; the incisors are reduced to a single tusk in each jaw ramus, i. e., two upper and two lower tusks. All the grinders are functional, but they have increased in complexity and now consist of six cusps and three crests. The trunk was still short, the head still long and narrow, the limbs heavier, but still relatively light. The elephants now spread into southern Asia and over Europe during the lower Miocene, giving rise to various collateral lines of evolution along their different routes of dispersal. They increased greatly in size and became more elephantine in appearance. They reached North America during the middle Miocene, and these four-tusked forms spread from Nebraska to Florida. The old-world stock shortened the chin and lost the lower pair of tusks during the Pliocene, giving rise to the mastodons and mammoths of the late Pliocene and Pleistocene, which reinvaded North America and ranged southward to the straits of Magellan. Our mastodon survived much later than the European mastodon, and the males sometimes show vestigial tusks in the lower jaw. The mammoth was the contempo rary of early man in Europe as the many excellent carvings of the stone age show, and probably also in North America, as somewhat vaguely pictured carved bone and associated flints indicate. They were so common over the northern hemisphere at that time that we have records of 1,635 fossil tusks, averaging 150 lbs., being exported from Siberia in a single year. Between 1820 and 1833, trawlers out of Happisburg, Norfolk, dredged 2,000 elephant molars from the submerged old land of the North Sea. (We had three true elephants in America during the Pleistocene-the Northern or Hairy Mammoth, the Southern or Columbian Mammoth, and the Imperial Mammoth, the latter standing 13 feet at the shoulder.) The family tree of our noblest of domesticated animals-the horse has been called the example de luxe of evolution, since no animal stock is more completely known or has a more spectacular history. Long domesticated the modern animal is found almost everywhere that man can live, and of many breeds. As wild animals, horses are found only in the Old World in moder times the arid plains of Central Asia and Africa. There are several species-horses, asses, zebras and quaggas-very uniform in tooth and skeletal characters, but strikingly different in appearance, because of the superficial difference in coloration and in the development of forelock, mane, tail and ears. They differ from all living animals in having a single toe on each foot. Their remotest ancestors were small five-toed plantigrade animals as were all of the earliest mammals. Hosts of fossil species are known, some extinct side lines especially adapted to certain environments, like the small mountain horses or the forest-dwelling and softer ground-inhabiting forms. Others were a part of the progressive line. The earliest known fossil horse you would not recognize as a horse. How do we know it was? By tracing backward step by step from the known. Nearly every stage of this ancestry is now complete, and we are as certain of the remote Tertiary form as we are of the present cart horse. The earliest well-known ancestral horse is the tiny Eohippus or Dawn horse of our early Eocene. It was about the size of a fox terrier, i. e., 11 to 14 inches high, with a short neck, long body, arched back, short legs and small teeth. The front feet had 4 functional toes, and a splint representing the first or thumb. The hind feet had 3 functional and 2 splints representing the first and fifth. It is significant that at that time the ancestral horse line is so generalized that a layman could not distinguish it from the contemporaneous ancestral rhinoceroses or tapirs. The second-stage Protorohippus of the middle Eocene was about the size and proportions of a whippet hound. The thumb splint had now disappeared from the front foot, and the little finger splint from the hind foot. The weight was beginning to center on the middle toe, but it required two or three million years more to completely suppress the lateral toes. If there were time, we might pass in review each stage of horse evolution-the Epihippus of the upper Eocene, the Mesohippus of the Oligocene, about the size of a sheep, the Miocene, Protohippus, Pliohippus, Neohipparion, etc. The upper Miocene Protohippus is in the direct line and may be briefly characterized. About 40 inches high, longer head, longer teeth, deeper jaws, shortened body, longer legs and feet, only the third toe normally reaching the ground, but the second and fourth were complete "dew claws" and helped to support the weight on soft ground. There were many varieties of three-toed horses, and in the late Tertiary they had spread pretty well over the world, being found in South America, Europe and Asia, as well as in North America. By Pleistocene time the horses had become monodactyl, varied, abundant and wide ranging. So countless were the herds that the Sheridan formation of the West was long known as the Equus beds from the abundance of their fossil remains. When, however, America was discovered, horses had become extinct in the western hemisphere as well as in native tra dition, although their bones are found associated with flint implements, pottery and fire refuse. They appear to have first been domesticated during the Neolithic, that is about 7000 B. C. in Europe, but probably at a much earlier date in Asia. Our modern work horse is descended directly from the European Neolithic horse, which was much like the Celtic pony. Descendants of this low-bred primitive race were distributed over Eurasia, where they are still represented by the Norwegian and Mongolian ponies. All the earlier horses of written history belonged to this type. It was improved by importations from Libya-the Arabs, for example, getting stallions and brood mares from Barbary, where the stock had suffered no ill effects during the Pleistocene glaciation, there having been no severity of climate in northern Africa. The course of evolution in the horses was not confined to the feet. It may be summarized as follows: Along with the disappearance of side toes went increase in length of leg and foot, especially the distal portion. Increased length of the lower leg and foot increased length of stride and, as the chief muscles are in the upper leg, the center of gravity was changed very little, consequently the swing was about as rapid but mechanical strain was greatly increased, so that strengthening at the expense of flexibility by consolidation of the lower leg and arm bones and conversion of ball and socket into pulley joints (ginglymoid) occurred. Lengthening of limbs for speed in grazing animals necessitates lengthening of the neck. Loss of toes was a hard ground adaptation for speed. The lengthening of the teeth which caused the deepening of the jaws was an adaptation for hard food and ensured more thorough mastication and a longer life span. Increase in size, although demanding an increased food supply, is a better defence against enemies or competitors. The evolution of the horse was from forest and swamp to grassy plains and went hand in hand with the evolution of the environment. Since monkeys are unaccountably not fashionable and we are very fond of horses here in Maryland, I show you for comparison a skeleton of a modern horse and man. Not only in the structure of all his physical parts, bone for bone, muscle for muscle, and nerve for nerve, is man fundamentally like the other mammals, but his specific organic functions are identical. We have the same diseases; we are similarly affected by the same drugs-in fact the whole wonderful advance of physiology and experimental medicine is built up on this truism. Have you ever thought of the countless generations of meat-eating humans involved in the specialization of the two human tape worms-the one passing its intermediate stage in beef and the other in pork and of which man alone is the host of the adult stage. The pre-humans were not meat-eaters, and we should not fail to take into account the improvement in nutrition in shortening the digestive processes and the stimulating properties of the proteins and their split products that a change in diet gave our ancestors the energy for other things. I have already mentioned the remoteness of man's relationship with the existing monkeys and apes. Unfortunately, we have but slight knowledge of the earlier stages which remain hidden in the unexplored regions of Asia and Africa, to which much evidence points as the original homes of a majority of the mammalian stocks that appeared in Europe and North America during the Tertiary. But we know much of our less remote fossil ancestors. Evidences of their slowly advancing skill in the fashioning of weapons and implements, in the discovery of the bow and the uses of fire are innumerable, and their skeletal remains are found over a period estimated at from 250,000 to over a million years. We know at least two, perhaps three extinct genera of men and at least five distinct human species. All the existing races of man-white, black, red and yellow-belong to the single zoological species which we modestly call Homo sapiens. I should say that our knowledge of the exact stages between non-human ape-like animals and man is as complete as was the knowledge of the evolution of the horse |