 CHAPTER IV. THE STRUGGLE FOR EXISTENCE. animal and bird mimicry and disguise. For every animal one discovers when observing carefully there must be ten unseen. This is partly because many animals burrow in the ground or get in underneath things and into dark corners, being what is called cryptozoic or elusive. But it is partly because many animals put on disguise or have in some way acquired a garment of invisibility. This is very common among animals, and it occurs in many forms and degrees. The reason why is so common is because the struggle for existence is often very keen, and the reasons why the struggle for existence is keen are four. First, there is the tendency to overpopulation in many animals, especially those of low degree. Second, there is the fact that the scheme of nature involves nutritive chains and successive incarnations, one animal depending upon another for food, and all in the long run on plants. Thirdly, every vigorous animal is a bit of a hustler given to insurgents and sticking out his elbows. There is a fourth great reason for the struggle for existence, namely the frequent changefulness of the physical environment which forces animals to answer back or die. But the first three reasons have most to do with the very common assumption of some sort of disguise. Even when an animal is in no sense a weakling, it may be very advantageous for it to be inconspicuous when it is resting, or when it is taking care of its young. Our problem is the evolution of elusiveness, so far at least as that depends on likeness to surroundings, on protective resemblance to other objects, and in its highest reaches on true mimicry. Colour permanently like that of surroundings. Many animals living on sandy places have a light brown colour, as is seen in some lizards and snakes. The green lizard is like the grass, and the green tree snake is inconspicuous among the branches. The spotted leopard is suited to the interrupted light at the forest, and it is sometimes hard to tell where the jungle ends and the striped tiger begins. There is no better case than the hare, or the partridge sitting a few yards off on the plowed field. Even a donkey grazing in the dusk is much more readily heard than seen. The experiment has been made of tethering the green variety of praying mantis on green herbage, fastening them with silk threads. They escape the notice of birds. The same is true when the brown variety is tethered on withered herbage. But if the green ones are put on brown plants, or the brown ones on green plants, the birds pick them off. Similarly, out of three hundred chickens in a field, two hundred forty white or black and therefore conspicuous, sixty spotted and inconspicuous, twenty-four were soon picked off by crows, but only one of these was spotted. This was not the proportion that there should have been if the mortality had been fortuitous. There is no doubt that it often pays an animal to be like its habitual surroundings, like a little piece of scenery if the animal is not moving. It is safe to say that in the process of time, wide departures from the safest coloration will be wiped out in the course of nature's sifting. But we must not be credulous, and there are three cautions to be borne in mind. One, an animal may be very like its surroundings without there being any protection implied. The arrow worms in the sea are as clear as glass, and so are many open sea animals. But this is because their tissues are so watery, with a specific gravity near that of the salt water, and the invisibility does not save them, always or often, from being swallowed by larger animals that gather the harvest of the sea. Two, among the cleverer animals it looks as if a creature sometimes sought out a spot where it was most inconspicuous. A spider may place itself in the middle of a little patch of lichen, where its self-effacement is complete. Perhaps it is more comfortable, as well as safer, to rest in surroundings the general color of which is like that of the animal's body. Three, the fishes that live among the coral reefs are startling in their brilliant coloration, and there are many different patterns. To explain this it has been suggested that these fishes are so safe among the mazy passages and endless nooks of the reefs that they can well afford to wear any color that suits their constitution. In some cases this may be true, but naturalists who have put on a diving suit and walked about among the coral have told us that each kind of fish is particularly suited to some particular place, and that some are suited for midday work and others for evening work. Sometimes there is a sort of box-and-cocks arrangement by which two different fishes utilize the same corner at different times. Gradual Change of Color The common shore crab shows many different colors and mottlings, especially when it is young. It may be green or gray, red or brown, and so forth, and it is often an admirable adjustment to the color of the rock pool where it is living. Experiments which require extension have shown that when the crab is malted, which it has to do very often when it is young, the color of the new shell tends to harmonize with the general color of the rocks and seaweed. How this is brought about we do not know. The color does not seem to change till the next malt, and not then unless there is some reason for it. A full-grown shore crab is well able to look after itself, and it is of interest to notice, therefore, that variety of coloration is mainly among the small individuals who have, of course, a much less secure position. It is possible, moreover, that the resemblance to the surroundings admits of more successful hunting, enabling the small crab to take its victim unawares. Professor Polton's experiments with the caterpillars of the small tortoise-shell butterfly showed that in black surroundings the pupae tend to be darker, in white surroundings lighter, in gilded boxes golden, and the same is true in other cases. It appears that the surrounding color affects the caterpillars through the skin during a sensitive period, the twenty hours immediately preceding the last twelve hours of the larval state. The result will tend to make the quiescent pupae less conspicuous during the critical time of metamorphosis. The physiology of this sympathetic coloring remains obscure. SEASONAL CHANGE OF COLORING The ptarmigan molts three times in the year. Its summer plumage is rather grouse-like above with a good deal of rufous brown. The back becomes much more gray in autumn. Almost all the feathers of the winter plumage are white. That is to say, they develop without any pigment and with numerous gas bubbles in their cells. Now, there can be no doubt that this white winter plumage makes the ptarmigan very inconspicuous amidst the snow. Sometimes one comes within a few feet of the crouching bird without seeing it, and this garment of invisibility may save it from the hungry eyes of golden eagles. Similarly, the brown stote becomes the white ermine, mainly by the growth of a new suit of white fur, and the same is true of the mountain hare. The ermine is all white except the black tip of its tail. The mountain hare in its winter dress is all white save the black tips of its ears. In some cases, especially in the mountain hare, it seems that individual hares may turn white by a loss of pigment as may occur in man. According to Mechnikov, the wandering amoeboid cells of the body, called phagocytes, may creep up into the hares and come back again with microscopic burdens of pigment. The place of the pigment is taken by gas bubbles, and that is what causes the whiteness. In no animals is there any white pigment, the white collar is like that of snow or foam. It is due to the complete reflection of the light from innumerable, minute surfaces of crystals or bubbles. The mountain hare may escape the fox the more readily because its whiteness makes it so inconspicuous against the background of snow, and yet at other times we have seen the creature standing out like a target on the dark moorland. So it cuts both ways. The ermine has almost no enemies except the gamekeeper, but its winter whiteness may help it to sneak upon its victims, such as grouse or rabbit, when there is snow upon the ground. In both cases, however, the probability is that the constitutional rhythm which leads to white hair in winter has been fostered and fixed for a reason quite apart from protection. The fact is that for a warm-blooded creature, whether bird or mammal, the physiologically best dress is a white one, for there is less radiation of the precious animal heat from white plumage or white pellage than from any other color. The quality of warm-bloodedness is a prerogative of birds and mammals, and it means that the body keeps an almost constant temperature day and night, year in and year out. This is affected by automatic internal adjustments, which regulate the supply of heat, chiefly from the muscles to the loss of heat, chiefly through the skin and from the lungs. The chief importance of this internal heat is that it facilitates the smooth continuance of the chemical processes on which life depends. If the temperature falls, as in hibernating mammals, whose warm-bloodedness is imperfect, the rate of this vital process is slowed down sometimes dangerously. Thus we see how the white coat helps the life of the creature. Rapid Color Change Bony flatfishes, like Pleus and Sol, have a remarkable power of adjusting their hue and pattern to the surrounding gravel and sand, so that it is difficult to find them even when we know that they are there. It must be admitted that they are also very quick to get a sprinkling of sand over their upturned side, so that only the eyes are left showing. But there is no doubt as to the exactness with which they often adjust themselves to be like a little piece of the substratum on which they lie. They will do this within limits and experimental conditions when they are placed on a quite artificial floor. Because these fishes are very palatable and are much sought after by such enemies as cormorants and otters, it is highly probable that their power of self-effacement often saves their life, and it may be affected within a few minutes, in some cases within a minute. In these self-effacing flatfishes we know with some precision what happens. The adjustment of color and pattern is due to changes in the size, shape, and position of mobile pigment cells, chromatophores, and the skin. But what makes the pigment cells change? The fact that a blind flatfish does not change its color gives us the first part of the answer. The color and the pattern of the surroundings must affect the eye. The message travels by the optic nerve to the brain. From the brain, instead of passing down the spinal cord, the message travels down the chain of sympathetic ganglia. From these it passes along the nerves which comes out of the spinal cord and control the skin. Thus the message reaches the color cells in the skin, and before you have carefully read these lines the flatfish has slipped on its gaiji's ring and become invisible. The same power of rapid color change is seen in cuttlefishes, where it is often an expression of nervous excitement, though it sometimes helps to conceal. It occurs with much subtlety in the ace of prawn, Hippolyte, which may be brown on a brown seaweed, green on sea lettuce or sea grass, red on red seaweed, and so on through an extensive repertory. According to the nature of the background, Professor Gamble writes, so is the nature of the pigments compounded so as to form a close reproduction both of its color and its pattern. A sweep of the shrimp net detaches a battalion of these sleeping prawns, and if we turn the motley into a dish and give us choice of seaweed, each variety after its kind will select the one with which it agrees in color and vanish. Both when young and when full grown the ace of prawn takes on the color of its immediate surroundings. At nightfall Hippolyte, of whatever color, changes to a transparent azure blue. Its validity gives place to a nervous restlessness. At the least tremor it leaps violently and often swims actively from one food plant to another. This blue fit lasts till daybreak and is then succeeded by the prawn's diurnal tint. Thus Professor Gamble continues, the color of an animal may express a nervous rhythm. The case of chameleons. The highest level at which rapid color change occurs is among lizards, and the finest exhibition of it is among the chameleons. These quaint creatures are characteristic of Africa, but they occur also in Andalusia, Arabia, Ceylon, and southern India. They are adapted for life on trees, where they hunt insects with great deliberateness and success. The protrusible tongue, ending in a sticky club, can be shot out for about seven inches in the common chameleon. Their hands and feet are split so that they grip the branches firmly, and the perhensible tail rivals some monkeys. When they wish they can make themselves very slim, contracting the body from side to side so that they are not very readily seen. In other circumstances, however, they do not practice self-effacement, but the very reverse. They inflate their bodies, having not only large lungs, but air sacs in connection with them. The throat bulges, the body sways from side to side, and the creature expresses its sentiments in a hiss. The power of color change is very remarkable, and depends partly on the contraction and expansion of the color cells, chromatophores, in the underskin or dermis, and partly on close-packed refractive granules and crystals of a waste-product called guanine. The repertory of possible colors in the common chameleon is greater than in any other animal except the acep prom. There is a legend of a chameleon which was brown in a brown box, green in a green box, and blue in a blue box, and dyed when put into one line with tartan. And there is no doubt that one and the same animal has a wide range of colors. The so-called chameleon, a nollus of North America, is so sensitive that a passing cloud makes it change its emerald hue. There is no doubt that a chameleon may make itself more inconspicuous by changing its color, being affected by the play of light on its eyes. A bright green hue is often seen on those that are sitting among strongly-illumined green leaves. But the color also changes with the time of day and with the animal's moods. A sudden irritation may bring about a rapid change. In other cases the transformation comes about very gradually. When the color change expresses the chameleon's feelings it might be compared to a blushing, but that is due to an expansion of the arteries of the face, allowing more blood to get into the capillaries of the underskin. The case of the chameleon is peculiarly interesting because the animal has two kinds of tactics, self-effacement on the one hand and bluffing on the other. There can be little doubt that the power of color change sometimes justifies itself by driving off intruders. Dr. Cyro Crossland observed that a chameleon attacked by a fox terrier turned round and opened its great pink mouth in the face of the advancing dog, at the same time rapidly changing color, becoming almost black. This roost succeeded every time, the dog turning off at once. In natural leafy surroundings the startling effect would be much greater, a sudden throwing off of the mantle of invisibility and the exposure of a conspicuous black body with a large red mouth. Lightnesses to other things. Dr. H. O. Forbes tells of a flat spider which presents a striking resemblance to a bird's dropping on a leaf. Years after he first found it he was watching in a forest in the Far East when his eye fell on a leaf before him which had been blotched by a bird. He wondered idly why he had not seen for so long another specimen of the bird dropping spider, or Nithoscatoides' dissipians, and drew the leaf towards him. Instantaneously he got a characteristic sharp nip. It was the spider after all. Here the color resemblance was enhanced by a form resemblance. But why should a prophet a spider to be like a bird dropping? Perhaps because it thereby escapes attention. But there is another possibility. It seems that some butterflies, allied to our blues, are often attracted to excrementitious material, and the spider Dr. Forbes observed had actually caught its victim. This is borne out by a recent observation by Dr. D. G. H. Carpenter, who found a Uganda bug closely resembling a bird dropping on sand. The bug actually settled down on a bird dropping on sand, and caught a blue butterfly which came to feed there. Some of the walking stick insects, belonging to the order of crickets and grasshoppers, orthoptera, have their body elongated and narrow, like a thin dry branch, and they have a way of sticking out their limbs at abrupt and diverse angles, which makes the resemblance to twigs very close indeed. Some of these quaint insects rest through the day and have the remarkable habit of putting themselves in a sort of cataleptic state. Many creatures turn stiff when they get a shock, or pass suddenly into new surroundings, like some of the sandhoppers when we lay them on the palm of our hand. But these twig insects put themselves into this strange state. The body is rocked from side to side for a short time, and then it stiffens. An advantage may be that even if they were surprised by a bird or a lizard they will not be able to betray themselves by even a tremor. Disguise is perfected by a remarkable habit, a habit which leads us to think of a whole series of different ways of lying low and saying nothing, which are often of life-preserving value. The top end of the series is seen when a fox plays possum. The leaf-butterfly kalama, conspicuously colored on its upper surface, is like a withered leaf when it settles down and shows the underside of its wings. Here again there is precise form resemblance, for the nerveurs on the wings are like the mid-rib and side veins on a leaf, and the touch of perfection is given in the presence of whitish spots which look exactly like the discolorations produced by lichens on leaves. An old entomologist, Mr. Jenner Ware, confessed that he repeatedly pruned off a caterpillar on a bush in mistake for a superfluous twig for many brownish caterpillars fasten themselves by their posterior claspers and by an invisible thread of silk from their mouth, and project from the branch at a twig-like angle. An insect may be the very image of a sharp prickle or a piece of soft moss. A spider may look precisely like a tiny knob on a branch or a fragment of lichen. One of the seahorses, phylopteryx, has frond-like tassels on various parts of its body so that it looks extraordinarily like the seaweeds among which it lives. In a few cases, for instance, among spiders, it has been shown that animals with a special protective resemblance to something else seek out a position where this resemblance tells, and there is urgent need for observations bearing on this selection of environment. Mimicry in the true sense. It sometimes happens that in one in the same place there are two groups of animals, not very nearly related, which are doubles of one another. Investigation shows that the members of the one group, always in the majority, are in some way specially protected, for instance, by being unpalatable. They are the mimicked. The members of the other group, always in the minority, have not got the special protection possessed by the others. They are the mimickers, though the resemblance is not, of course, associated with any conscious imitation. The theory is that the mimickers live on the reputation of the mimicked. If the mimicked are left alone by birds because they have a reputation for unpalatability, or because they are able to sting, the mimickers survive, although they are palatable and stingless. They succeed, not through any virtue of their own, but because of their resemblance to the mimicked, for whom they are mistaken. There are many cases of mimetic resemblance so striking and so subtle that it seems impossible to doubt that the thing works. There are other cases which are rather far-fetched, and may be somewhat of the nature of coincidences. Thus although Mr. Bates tells us that he repeatedly shot hummingbird moths in mistake for hummingbirds, we cannot think that this is a good illustration of mimicry. What is needed for many cases is what is forthcoming for some, namely, experimental evidence. For instance, that the unpalatable mimicked butterflies are left in relative peace, while similar palatable butterflies are persecuted. It is also necessary to show that the mimickers do actually consort with a mimicked. Some beetles and moths are curiously wasp-like, which may be a great advantage. The common drone fly is superficially like a small bee. Some harmless snakes are very like poisonous species, and Mr. Wallace maintained that the powerful friar birds of the Far East are mimicked by the weak and timid orioles. When the model is unpalatable or repulsive or dangerous, and the mimic the reverse, the mimicry is called Batesian after Mr. Bates. But there is another kind of mimicry called Malurian after Fritz Muller, where the mimic is also unpalatable. The theory in this case is that the mimicry serves as mutual assurance, the members of the ring getting on better by consistently presenting the same appearance, which has come to mean to possible enemies a signal, no li me tunjere, li me alone. There is nothing out of the question in this theory, but it requires to be taken in a critical spirit. It leads us to think of warning colors, which are the very opposite of the disguises which we are now studying. Some creatures like skunks, magpies, coral snakes, cobras, brightly colored tree frogs, are obtrusive rather than elusive, and the theory of Alphid Russell Wallace was that the flaunting conspicuousness serves as a useful advertisement, impressing itself on the memories of inexperienced enemies who soon learn to leave creatures with warning colors alone. In any case, it is plain that an animal which is as safe as a wasp or a coral snake can afford to wear any suit of clothes it likes. MASKING The episode in Scottish history called The Walking Wood of Burnham, when the advancing troop masked their approach by cutting down branches of the trees, has had its counterpart in many countries, but it is also enacted on the seashore. There are many kinds of crabs that put on disguise with what looks like deliberateness. The sand crab takes a piece of seaweed, nibbles at the end of it, and then rubs it on the back of the carapace or on the legs so that it fixes to the bristles. As the seaweed continues to live, the crab soon has a little garden on its back which masks the crab's real nature. It is most effective camouflaging, but if the crab continues to grow, it has to molt, and that means losing the disguise. It is then necessary to make a new one. The crab must have on the seashore something corresponding to a reputation. That is to say, other animals are clearly or dimly aware that the crab is a voracious and combative creature. How useful to the crab, then, to have its appearance cloaked by a growth of innocent seaweed, or sponge, or zoophyte? It will enable the creature to sneak upon its victims or to escape the attentions of its own enemies. If a narrow-beaked crab is cleaned artificially, it will proceed to clothe itself again. The habit has become instinctive, and it must be admitted that while a particular crab prefers a particular kind of seaweed for its dress, it will cover itself with unsuitable and even conspicuous material, such as pieces of colored cloth if nothing better is available. The disguise differs greatly, for one crab is masked by a brightly colored and unpalatable sponge densely packed with flinty needles. Another cuts off the tunic of a sea squirt and throws it over its shoulders. Another trundles about a bivalve shell. The facts recall the familiar case of the hermit crab, which protects its soft tail by tucking it into the empty shell of a periwinkle or a welk or some other sea snail. And that case leads on to the elaboration known as commensalism, where the hermit crab fixes sea anemones on the back of its borrowed house. The advantage here is beyond that of masking, for the sea anemone can sting, which is a useful quality in a partner. That this second advantage may become the main one is evident in several cases where the sea anemone is born, just like a weapon, on each of the crustacean's great claws. Moreover, as the term commensalism, eating at the same table, suggests, the partnership is mutually beneficial. For the sea anemone is carried about by the hermit crab, and it doubtless gets its share of crumbs from its partner's frequent meals. There is a very interesting sidelight on the mutual benefit, in the case of a dislodged sea anemone, which sulked for a while and then waited in a state of preparedness until a hermit crab passed by and touched it, whereupon the sea anemone gripped and slowly worked itself up, onto the back of the shell. Other kinds of elusiveness. There are various kinds of disguise which are not readily classified. A troop of cuttlefish swimming in the sea is a beautiful sight. They keep time with one another in their movements, and they show the same change of color almost at the same moment. They are suddenly attacked, however, by a small shark, and then comes a simultaneous discharge of sepia from their ink bags. There are clouds of ink in the clear water, for, as Professor Hickson put it, the cuttlefishes have thrown dust in the eyes of their enemies. One can see a newborn cuttlefish do this a minute after it escapes from the egg. Very beautiful is the way in which many birds, like our common chefinch, disguise the outside of their nest with moss and lichen, and other trifles felted together, so that the cradle is as inconspicuous as possible. There seems to be a touch of art in fastening pieces of spider's web on the outside of a nest. How curious is the case of the tree sloth of South American forests that walk slowly, back downwards, along the undersides of the branches, hanging on by its long curved fingers and toes. It is a nocturnal animal, and therefore not in special danger, but when resting during the day it is almost invisible, because its shaggy hair is so like certain lichens and other growths on the branches. But the protective resemblance is enhanced by the presence of a green alga, which actually lives on the surface of the sloth's hairs, an alga like the one that makes tree stems in gate posts, green and damp weather. There is no commoner sight in the early summer than the cuckoo spit on the grasses and herbage by the wayside. It is conspicuous, and yet it is said to be left severely alone by almost all creatures. In some way it must be a disguise. It is a sort of soap made by the activity of small frog hoppers, while they are still in the wingless, larval state, before they begin to hop. The insect pierces with its sharp mouth-parts the skin of the plant, and sucks in sweet sap, which by and by overflows over its body. It works its body up and down many times, whipping an air, which mixes with the sugary sap, reminding one of how whipped egg is made. But along with the sugary sap and the air, there is a little ferment from the food canal, and a little wax from glands on the skin. And the four things mixed together make it kind of soup, which lasts through the heat of the day. There are many other modes of disguise besides those that we have been able to illustrate. Indeed, the biggest fact is that there are so many, for it brings us back to the idea that life is not an easy business. It is true, as Walt Whitman says, that animals do not sweat and whine about their condition. Perhaps it is true, as he says, that not one is unhappy over the whole earth. But there is another truth, that this world is not a place for the unlit lamp and the ungirt loin, and that when a creature has not armor or weapons or cleverness it must find some path of safety or go back. One of these paths of safety is disguise, and we have illustrated its evolution. THE OUTLINE OF SCIENCE Volume 1 by J. ARTHUR TOMPSON Chapter 5 The Ascent of Man No one thinks less of Sir Isaac Newton because he was born as a very puny infant, and no one should think less of a human race because it sprang from a stock of arboreal mammals. There is no doubt as to man's apartness from the rest of creation when he is seen at his best, a little lower than the angels crowned with glory and honour. What a piece of work as a man! How noble in reason! How infinite in faculty! In form and moving! How express and admirable! In action! How like an angel! In apprehension! So like a god! Nevertheless all the facts point to his affiliation to the stock to which monkeys and apes also belong. Not, indeed, that man is descended from any living ape or monkey, but it is rather that he and they have sprung from a common ancestry, are branches of the same stem. This conclusion is so momentous that the reasons for accepting it must be carefully considered. They were expounded with masterly skill in Darwin's Descent of Man in 1871, a book which was but an expansion of a chapter in the Origin of Species, 1859. Anatomical Proof of Man's Relationship with a Simeon Stock The anatomical structure of man is closely similar to that of the anthropoid apes, the gorilla, the orang, the chimpanzee, and the gibbon. Bone for bone, muscle for muscle, blood vessel for blood vessel, nerve for nerve, man and ape agree. As the conservative anatomist Sir Richard Owens said, there is between them an all-pervading similitude of structure. Differences, of course, there are, but they are not momentous except man's big brain, which may be three times as heavy as that of a gorilla. The average human brain weighs about forty-eight ounces. The gorilla brain does not exceed twenty ounces at its best. The capacity of the human skull is never less than fifty-five cubic inches. In the orang and the chimpanzee the figures are twenty-six and twenty-seven-and-a-half, respectively. We are not suggesting that the most distinctive features of man are such as can be measured in weight, but it is important to notice that the main seat of his mental powers is physically far ahead of that of the highest of the anthropoid apes. Man alone is thoroughly erect after his infancy has passed. His head, weighted with a heavy brain, does not droop forward as the apes does. With his erect attitude there is perhaps to be associated his more highly developed focal organs. Compared with an anthropoid ape, man has a bigger and more upright forehead, a less pertrusive face region, smaller cheekbones and eyebrow ridges, and more uniform teeth. He is almost unique in having a chin. Man plants the sole of his foot flat on the ground. His big toe is usually in a line with the other toes, and he has a better heel than any monkey has. The change in the shape of the head is to be thought of in connection with the enlargement of the brain, and also in connection with the natural reduction of the muscle region when the hand was freed from being an organ of support, and became suited for grasping the food and conveying it to the mouth. Everyone is familiar in man's clothing with traces of the past persisting in the present, though their use has long since disappeared. There are buttons on the back of the waist of the morning coat to which the tails of the coat used to be fastened up, and there are buttons, occasionally with button holes, at the wrist which were once useful in turning up the sleeve. The same is true of man's body, which is a veritable museum of relics. Some anatomists have made out a list of over a hundred of these vestigial structures, and though this number is perhaps too high, there is no doubt that the list is long. In the inner upper corner of the eye there is a minute tag, but larger in some races than in others, which is the last dwindling relic of the third eyelid used in cleaning the front of the eye, which most mammals possess, in a large and well-developed form. It can be easily seen, for instance, in ox and rabbit. In man and in monkeys it has become a useless vestige, and the dwindling must be associated with the fact that the upper eyelid is much more mobile in man and monkeys than in the other mammals. The vestigial third eyelid in man is enough of itself to prove his relationship with the mammals, but is only one example out of many. Some of these are discussed in the article dealing with the human body, but we may mention the vestigial muscles going to the ear-trumpet, man's dwindling counterpart of the skin-twitching muscle, which we see a horse use when he jerks a fly off his flanks, and the short tail which in the seven weeks old human embryo is actually longer than the leg. Without committing ourselves to a belief in the entire uselessness of the vermaform appendix, which grows out as a blind alley at the juncture of the small intestine with the large, we are safe in saying that it is a dwindling structure, the remains of a blind gut which must have been capacious and useful in ancestral forms. In some mammals, like the rabbit, the blind gut is the bulkiest structure in the body, and bears the vermaform appendix at its far end. In man the appendix alone is left and it tells its tail. It is interesting to note that it is usually longer in the oarang than in man, and that it is very variable as dwindling structures tend to be. One of the unpleasant expressions of this variability is the liability to go wrong, hence appendicitis. Now these vestigial structures are, as Darwin said, like the unsounded, that is, functionless letters and words, such as the O in Leopard, the B in Doubt, the G in Rain. They are of no use, but they tell us something of the history of the words. So do men's vestigial structures reveal his pedigree. They must have an historical or evolutionary significance. No other interpretation is possible. Some men, oftener than women, show on the interned margin of the ear trumpet or pinna a little conical projection of great interest. It is a vestige of the tip of the pointed ear of lower mammals, and it is well-named Darwin's Point. It was he who described it as a surviving symbol of the stirring times and dangerous days of man's animal youth. Physiological proof of man's relationship with a simian stock. The everyday functions of the human body are practically the same as those of the anthropoid ape. And similar disorders are common to both. Monkeys may be infected with certain microbes to which man is peculiarly liable, such as the bacillus of tuberculosis. Darwin showed that various human gestures and facial expressions have their counterparts in monkeys. The sneering curl of the upper lip, which tends to expose the canine tooth, is a case in point, though it may be seen in many other mammals besides monkeys, in dogs, for instance, which are at some considerable distance from the simian branch to which man's ancestors belonged. When human blood is transfused into a dog or even a monkey, it behaves in a hostile way to the other blood, bringing about a destruction of the red-blood corpuscles. But when it is transfused into a chimpanzee, there is a harmonious mingling of the two. This is a very literal demonstration of man's blood relationship with the higher apes. But there is a finer form of the same experiment. When the blood fluid, or serum, of a rabbit, which has had human blood injected into it, is mingled with human blood, it forms a cloudy precipitate. It forms almost as marked a precipitate when it is mingled with the blood of an anthropoid ape. But when it is mingled with the blood of an American monkey, there is only a slight clouding after a considerable time and no actual precipitate. When it is added to the blood of one of the distantly related half-monkeys or lemurs, there is no reaction, or only a very weak one. With the blood of mammals off the simian line altogether, there is no reaction at all. Thus, as a distinguished anthropologist, Professor Schwabbe has said, we have in this not only a proof of the literal blood relationship between man and apes, but the degree of relationship with the different main groups of apes can be determined beyond possibility of mistake. We can imagine how this modern line of experiment would have delighted Darwin. Embryological Proof of Man's Relationship with the Simian Stock In his individual development, man does in some measure climb up his own genealogical tree. Stages in the development of the body during its nine months of antenatal life are closely similar to stages in the development of the anthropoid embryo. Babies born in times of famine or siege are sometimes, as it were, imperfectly finished, and sometimes have what may be described as monkey-ish features in ways. A visit to an institution for the care of children who show arrested, defective, or disturbed development leaves one sadly impressed with the risk of slipping down the rungs of the steep ladder of evolution. And even in adults, the occurrence of serious nervous disturbance, such as shell shock, is sometimes marked by relapses to animal ways. It is a familiar fact that a normal baby reveals the past in its surprising power of grip, and the careful experiments of Dr. Louis Robinson showed that an infant three weeks old could support its own weight for over two minutes, holding on to a horizontal bar. In many cases no sign of distress is evinced and no cry uttered until the grasp begins to give way. This persistent grasp probably points back to the time when the baby had to cling to its arboreal mother. The human tail is represented in the adult by the fusion of four or five vertebrae forming the cockaxe at the end of the backbone, and is normally concealed beneath the flesh, but in the embryo the tail projects freely and is movable. Up to the sixth month of the antenatal sleep the body is covered, all but the palms and soles, with longish hair, the lanugo, which usually disappears before birth. This is a stage in the normal development which is reasonably interpreted as a recapitulation of a stage in the racial evolution. We draw this inference when we find that the unborn offspring of an almost hairless whale has an abundant representation of hairs. We must draw a similar inference in the case of man. It must be noticed that there are two serious errors in the careless statement often made that man in his development is at one time like a little fish, at a later stage like a little reptile, at a later stage like a little primitive mammal, and eventually like a little monkey. The first error here is that the comparison should be made with embryo fish, embryo reptile, embryo mammal, and so on. It is in the making of the embryos that the great resemblance lies. When the human embryo shows the laying down of the essential vertebrate characters, such as brain and spinal cord, then it is closely comparable to the embryo of a lower vertebrate at a similar stage. When, at a subsequent stage, its heart, for instance, is about to become a four-chambered mammalian heart, it is closely comparable to the heart of, let us say, a turtle, which never becomes more than three-chambered. The point is that in the making of the organs of the body, say, brain and kidneys, the embryo of man pursues a path closely corresponding to the path followed by the embryos of other backbone to animals lower in the scale. But at successive stages it parts company with these, with the lowest first and so on in succession. A human embryo is never like a little reptile, but the developing organs pass through stages which very closely resemble the corresponding stages in lower types, which are in a general way ancestral. The second error is that every kind of animal, man included, has from the first a certain individuality, with peculiar characteristics which are all its own. This is expressed by the somewhat difficult word specificity, which just means that every species is itself and no other. So in the development of the human embryo, while there are close resemblances to the embryos of apes, monkeys, other mammals, and even at earlier stages still, to the embryos of reptile and fish, it has to be admitted that we are dealing from first to last with a human embryo with peculiarities of its own. Every human being begins his or her life as a single cell, a fertilized egg cell, a treasure house of all the ages. For in this living microcosm, only a small fraction, one one hundred twenty-fifth of an inch in diameter, there is condensed, who can imagine how, all the natural inheritance of man, all the legacy of his parentage, of his ancestry, of his long pre-human pedigree. Darwin called the pinhead brain of the ant the most marvelous atom of matter in the world, but the human ovum is more marvelous still. It has more possibilities in it than any other thing, yet without fertilization it will die. The fertilized ovum divides and redivides. There results a ball of cells and a sack of cells. Gradually the vision of labor becomes the rule. There is a laying down of nervous system and food canal, muscular system and skeleton, and so proceeds what is learnedly called differentiation. Out of the apparently simple there emerges the obviously complex. As Aristotle observed more than two thousand years ago, in the developing egg of the hen there soon appears the beating heart. There is nothing like this in the non-living world, but to return to the developing human embryo there is formed from and above the embryonic food canal a skeletal rod which is called the notochord. It thrills the imagination to learn that this is the only supporting axis that the lower orders of the backbone race possess. The curious thing is that it does not become the backbone, which is certainly one of the essential features of the vertebrate race. The notochord is the supporting axis of the pioneer backbone to animals, namely the lancelets and the round mouths, also called cyclostomes, such as the lamprey. They have no backbone in the strict sense, but they have this notochord. It can easily be dissected out in the lamprey, a long gristly rod. It is surrounded by a sheath which becomes the backbone of most fishes and all higher animals. The interesting point is that although the notochord is only a vestige in the adults of these types, it is never absent from the embryo. It occurs even in man, a short-lived relic of the primeval supporting axis of the body. It comes and then it goes, leaving only minute traces in the adult. We cannot say that it is of any use, unless it serves as a stimulus to the development of its substitute, the backbone. It is only a piece of preliminary scaffolding, but there is no more eloquent instance of the living hand of the past. One other instance must suffice of what Professor Lull caused the wonderful changes wrought in the dark of the antinatal period, which recapitulate in rapid abbreviation the great evolutionary steps which were taken by man's ancestors during the long night of the geological past. On the sides of the neck of the human embryo there are four pairs of slits, the visceral clefts, openings from the beginning of the food canals to the surface. There is no doubt as to their significance. They correspond to the gill slits of fishes and tadpoles. Yet in reptiles, birds and mammals, they have no connection with breathing, which is their function in fishes and amphibians. Indeed, they are not of any use at all, except that the first becomes the Eustachian tube, bringing the air passage into connection with the back of the mouth, and that the second and third have to do with the development of a curious organ called the thymus gland. Persistent nevertheless, these gill slits are, recalling even in man, an aquatic ancestry of many millions of years ago. When all these lines of evidence are considered, they are seen to converge in the conclusion that man is derived from a simian stock of mammals. He is solidary, with the rest of creation. To quote the closing words of Darwin's Descent of Man, We must, however, acknowledge, as it seems to me, that man with all his noble qualities, with sympathy which feels for the most debased, with benevolence which extends not only to other men, but to the humblest living creature, with his godlike intellect which is penetrated into the movements and constitution of the solar system. With all these exalted powers, man still bears in his bodily frame the indelible stamp of his lowly origin. We should be clear that this view does not say more than that man sprang from a stock common to him and to the higher apes. Those who are repelled by the idea of man's derivation from a simian type should remember that the theory implies rather more than this, namely, that man is the outcome of a genealogy which has implied many millions of years of experimenting and sifting, the groaning and travailing of a whole creation. Speaking of man's mental qualities, Sir Ray Lancaster says, They justify the view that man forms a new departure in the gradual unfolding of nature's predestined plan. In any case, we have to try to square our views with the facts, not the facts with our views, and while one of the facts is that man stands unique and apart, the other is that man is a skyen of a progressive simian stock. Naturalists have exposed the pit whence man has been digged and the rock whence he has been hewn, but it is surely a heartening encouragement to know that it is an assent, not a descent, that we have behind us. There is wisdom in Pascal's maxim. It is dangerous to show man too plainly how like he is to the animals, without at the same time reminding him of his greatness. It is equally unwise to impress him with his greatness and not with his lowliness. It is worse to leave him in ignorance of both, but it is very profitable to recognize the two facts. Man's Pedigree The facts of anatomy, physiology and embryology of which we have given illustrations all point to man's affiliation with the order of monkeys and apes. To this order is given the name primates, and our first and second question must be when and whence the primates began. The rock record answers the first question, the primates emerged about the dawn of the Eocene era when grass was beginning to cover the earth with a garment. Their ancestral home was in the north in both hemispheres, and then they migrated to Africa, India, Mele, and South America. In North America the primates soon became extinct, and the same thing happened later on in Europe. In this case, however, there was a repeepling from the south in the lower Myocene, and then a second extinction in the upper Pliocene before man appeared. There is considerable evidence in support of Professor R. S. Lull's conclusion that in southern Asia, Africa, and South America the evolution of primates was continuous since the first great southward migration, and there is, of course, an abundant modern representation of primates in these regions today. As to the second question, whence the primates sprang, the answer must be more conjectural. But it is a reasonable view that carnivores and primates sprang from a common insectivore stock, the one order diverging towards flesh-eating and hunting on the ground, the other order diverging towards fruit-eating and arboreal habits. There is no doubt that the insectivores, including shrews, tree-shrews, hedgehog, mole, and the like, were very plastic and progressive mammals. What followed in the course of ages was the divergence of branch after branch from the main primate stem. First there diverged the South American monkeys on a line of their own, and then the Old World monkeys, such as the macaques and baboons. Ages passed and the main stems gave off in the Iligocene period, the branch now represented by the small anthropoid apes, the gibbon and the shemang. Distinctly later there diverged the branch of the large anthropoid apes, the gorilla, the chimpanzee, and the orang. That left a generalized humanoid stock separated off from all monkeys and apes, and including the immediate precursors of man. When this sifting out of a generalized humanoid stock took place remains very uncertain. But some authorities referring it to the myocene, others to the early Pliocene. Some would estimate its date at half a million years ago, others at two million. The fact is that questions of chronology do not as yet admit a scientific statement. We are infirmer, though still in certain ground, when we state the probability that it was in Asia that the precursors of man were separated off from monkeys and apes, and began to be terrestrial rather than arboreal. Professor Lull points out that Asia is nearest to the oldest known human remains in Java, and that Asia was the seed of the most ancient civilizations and the original home of many domesticated animals and cultivated plants. The probability is that the cradle of the human race was in Asia. This recording is by Mark Smith of Simpsville, South Carolina. At this point it will be useful to consider man's arboreal apprenticeship and how he became a terrestrial journeyman. Professor Wood Jones has worked out very convincingly the thesis that man had no direct four-footed ancestry, but that the primate stock to which he belongs was from its first divergence, arboreal. He maintains that the leading peculiarities of the immediate precursors of man were wrought out of a long arboreal apprenticeship. The first great gain of arboreal life on bipedal erect lines, not after the quadrupedal fashion of tree sloths, for instance, was the emancipation of the hand. The foot became the supporting and branch-gripping member, and the hand was set free to reach upward, to hang on by, to seize the fruit, to lift it and hold it to the mouth, and to hug the young one close to the breast. The hand thus set free has remained plastic, a generalized, not a specialized member, much as followed from man's handiness. The arboreal life had many other consequences. It led to an increased freedom of movement of the thigh on the hip joint, to muscular arrangements for balancing the body on the leg, to making the backbone a supple yet stable curved pillar, to a strongly developed collarbone which is only found well formed when the forelimb is used for more than support, and to a power of opposing the thumb and the big toe to the other digits of the hand and foot, an obvious advantage for branch-gripping. But the evolution of a free hand made it possible to dispense with protrusive lips and gripping teeth. Thus began the recession of the snout region, the associated enlargement of the brain box, and the bringing of the eyes to the front. The overcrowding of the teeth that followed the shortening of the snout was one of the taxes on progress of which modern man is often reminded in his dental troubles. Another acquisition associated with arboreal life was a greatly increased power of turning the head from side to side, a mobility very important in locating sounds and exploring with the eyes. Furthermore, there came about a flattening of the chest and of the back, and the movements of the midriff or diaphragm came to count for more in respiration than the movements of the ribs. The sense of touch came to be of more importance and the sense of smell of less. The part of the brain receiving tidings from hand and eye and ear came to predominate over the part for receiving olfactory messages. Finally, the need for carrying the infant about among the branches must surely have implied an intensification of family relations and favored the evolution of gentleness. It may be urged that we are attaching too much importance to the arboreal apprenticeship, since many tree-loving animals remain today very innocent creatures. To this reasonable objection there are two answers. First that in its many acquisitions the arboreal evolution of the humanoid precursors of man prepared the way for the survival of a human type, marked by a great step in brain development, and second that the passage from the humanoid to the human was probably associated with the return to Mother Earth. According to Professor Lowell, to whose fine textbook, Organic Evolution, 1917, we are much indebted climatic conditions in Asia and the Myocene or early Pliocene were such as to compel the descent of the pre-human ancestor from the trees, a step which was absolutely essential to further human development. Continental elevation and consequent aridity led to a dwindling of the forest and forced the ape-man to come to earth, and at the last arose the man. According to Lowell, the descent from the trees was associated with the assumption of a more erect posture, with increased liberation and plasticity of the hand, with becoming a hunter, with experiments towards clothing and shelter, with an exploring habit, and with the beginning of communal life. It is a plausible view that the transition from the humanoid to the human was affected by a discontinuous variation of considerable magnitude, what is nowadays called a mutation, and that it had mainly to do with the brain and the vocal organs. But given the gains of the arboreal apprenticeship, the stimulus of an enforced descent to terra firma, and an evolving brain and voice, we can recognize accessory factors which help success to succeed. Perhaps the absence of great physical strength prompted reliance on wits, the prolongation of infancy would help to educate the parents in gentleness, the strengthening of the feeling of kinship would favor the evolution of family and social life, of which there are many anticipations at lower levels. There is much truth in the saying, man did not make society, society made man. A continuation of the story will deal with the emergence of the primitive types of man and the gradual ascent of the modern species. Tentative Men So far the story has been that of the sifting out of a humanoid stock and of the transition to humankind, from the ancestors of apes and men to the man-ape, from the ancestors of apes and men to the man-ape, and from the man-ape to man. It looks as if the sifting out process had proceeded further, for there were several human branches that did not lead on to the modern type of man. One. The first of these is represented by the scanty-fossil remains known as Pythocanthropus erectus, found in Java in fossiliferous beds which date from the end of the Pliocene, or the beginning of the Pleostocene era. Perhaps this means half a million of years ago, and the remains occurred along with those of some mammals which are now extinct. Unfortunately, the remains of Pythocanthropus, the erect, consisted only of a skullcap, a thighbone, and two-backed teeth, so it is not surprising that experts should differ considerably in their interpretation of what was found. Some have regarded the remains as those of a large gibbon, others as those of a pre-human ape-man, and others as those of a primitive man off the main line of ascent. According to Sir Arthur Keith, Pythocanthropus was a being human in stature, human in gait, human in all its parts, save its brain. The thighbone indicates a height of about five feet seven inches, one inch less than the average height of the men of today. The skullcap indicates a low, flat forehead, beatling brows, and a capacity about two-thirds of the modern size. The remains were found by Dubois in 1894 in Trinil in Central Java. 2. The next offshoot is represented by the Heidelberg man, Homo Heidelbergensis, discovered near Heidelberg in 1907 by Dr. Shirtensack. But the remains consisted only of a lower jaw and its teeth. Along with this relic were bones of various mammals, including some long since extinct in Europe, such as elephant, rhinoceros, bison, and lion. The circumstances indicate an age of perhaps 300,000 years ago. There were also very crude flint implements, or eoliths. But the teeth are human teeth, and the jaw seems transitional between that of an anthropoid ape and that of man. Thus there was no chin. According to most authorities, the lower jaw from the Heidelberg sandpit must be regarded as a relic of a primitive type off the main line of human ascent. 3. It was in all probability in the Pliocene that there took origin the Neanderthal species of man, Homo Neanderthalensis, first known from remains found in 1856 in the Neanderthal ravine near Dusseldorf. According to some authorities, Neanderthal man was living in Europe a quarter of a million years ago. Other specimens were afterwards found elsewhere, for instance in Belgium, the men of Spee, in France, in Croatia, and at Gibraltar, so that a good deal is known of Neanderthal man. He was a loose limb fellow, short of stature and of slouching gait, but a skillful artificer, fashioning beautifully worked flints with a characteristic style. He used fire, he buried his dead reverently and furnished them with an outfit for a long journey, and he had a big brain. But he had great beatling ape-like eyebrow ridges and massive jaws, and he showed simian characters swarming in the details of his structure. In most of the points in which he differs from modern man, he approaches the anthropoid apes, and he must be regarded as a low type of man off the main line. Huxley regarded the Neanderthal man as a low form of the modern type, but expert opinion seems to agree rather with the view maintained in 1864 by Professor William King of Galway, that the Neanderthal man represents a distinct species off the main line of ascent. He disappeared with apparent suddenness, like some aboriginal races today, about the end of the fourth great ice age. But there is evidence that before he ceased to be, there had emerged a successor, rather than a descendant, the modern man. Four. Another offshoot from the main line is probably represented by the pilped-down man, found in Sussex in 1912. The remains consisted of the walls of the skull, which indicate a large brain, and a high forehead without the beatling eyebrows of the Neanderthal man and Pythocanthropus. The find included a tooth and part of a lower jaw, but these perhaps belong to some ape for they are very discrepant. The pilped-down skull represents the most ancient human remains as yet found in Britain, and Dr. Smith Woodward's establishment of a separate genus, Eoanthropus, expresses his conviction that the pilped-down man was off the line of the evolution of the modern type. If the tooth and piece of lower jaw belonged to the pilped-down skull, then there was a remarkable combination of ape-like and human characters. As regards the brain, inferred from the skull walls, Sir Arthur Keith says, quote, All the essential features of the brain of modern man are to be seen in the braincast. There are some which must be regarded as primitive. There can be no doubt that it is built on exactly the same lines as our modern brains. A few minor alterations would make it in all respects a modern brain. Although our knowledge of the human brain is limited, there are large areas to which we can assign no definite function. We may rest assured that a brain which was shaped in a mold so similar to our own was one which responded to the outside world as ours does. Pilped-down man saw, heard, felt, thought, and dreamt, much as we do still, end quote. And this was one hundred fifty thousand years ago at a modern estimate, and some would say half a million. There is neither agreement nor certainty as to the antiquity of man, except that the modern type was distinguishable from its collateral hundreds of thousands of years ago. The general impression left is very grand. In remote antiquity the primate stem diverged from the other orders of mammals, it sent forth its tentative branches, and the result was a tangle of monkeys. Ages passed and the monkeys were left behind, while the main stem, still probing its way, gave off the anthropoid apes, both small and large. But they too were left behind, and the main line gave off other experiments, indications of which we know in Java, at Heidelberg, in the Neanderthal, and at Pilped-down. None of these lasted or was made perfect. They represent tentative men who had their day and ceased to be our predecessors rather than our ancestors. Still the main stem goes on evolving, and who will be bold enough to say what fruit it has yet to bear? Primitive men. Ancient skeletons of men of the modern type have been found in many places, for instance Combe-Capelle in Dordonia, Galley Hill in Kent, Gromagnon in Paragord, Mentone on the Riviera, and they are often referred to as cavemen or men of the early Stone Age. They had large skulls, high foreheads, well-marked chins, and the other features such as modern man possesses. They were true men at last, that is to say, like ourselves. The spirited pictures they made on the walls of the caves in France and Spain show artistic sense and skill. Well-finished statuettes resembling nude female forms are also known. The elaborate burial customs point to a belief in life after death. They made stone implements, knives, scrapers, gravers, and the like of the type known as Paleolithic, and these show interesting gradations of skill and peculiarities of style. The cavemen live between the Third and Fourth Ice Ages, along with Cave Bear, Cave Lion, Cave Hyena, mammoth, woolly rhinoceros, Irish elk, and other mammals now extinct, taking us back to thirty to fifty thousand years ago, and many would say, much more. Some of the big-brained skulls of these Paleolithic cavemen show not a single feature that could be called primitive. They show teeth which in size and form are exactly the same as those of a thousand generations afterwards, and suffering from gum-boil too. There seems little doubt that these vigorous Paleolithic cavemen of Europe were living for a while contemporaneously with the men of Neanderthal, and it is possible that they directly or indirectly hastened the disappearance of their more primitive collateral. Curiously enough, however, they had not themselves adequate lasting power in Europe, for they seemed for the most part to have dwindled away, leaving perhaps stray present-day survivors in isolated districts. The probability is that after their decline Europe was repealed by immigrants from Asia. It cannot be said that there is any inherent biological necessity for the decline of a vigorous race. Many animal races go back for millions of years, but in mankind the historical fact is that a period of great racial vigor and success is often followed by a period of decline, perhaps leading to practical disappearance as a definite race. The causes of this waning remain very obscure, sometimes environmental, sometimes constitutional, sometimes competitive. Sometimes the introduction of a new parasite, like the malaria organism, may have been to blame. After the Ice Ages had passed, perhaps 25,000 years ago, the Paleolithic culture gave place to the Neolithic. The men who made rudely dressed but often beautiful stone implements were succeeded or replaced by men who made polished stone implements. The earliest inhabitants of Scotland were of this Neolithic culture, migrating from the continent when the ice fields of the Great Glaciation had disappeared. Their remains are often associated with the 50-foot beach, which, down now high and dry, was the seashore in early Neolithic days. Much is known about these men of the polished stones. They were hunters, fowlers, and fishermen. Without domesticated animals or agriculture, short folk, two or three inches below the present standard, living an active, strenuous life. Similarly, for the South, Sir Arthur Keith pictures for us a Neolithic community at Coldrum in Kent, dating from about 4,000 years ago, a few ticks of the geological clock. It consisted, in this case, of agricultural pioneers, men with large heads and big brains, about two inches shorter in stature than the modern British average, five-foot-eight inches, with better teeth and broader palates than men have in these days of soft food, with beliefs concerning life and death similar to those that swayed their contemporaries in western and southern Europe. Very interesting is the manipulative skill they showed on a large scale in erecting standing stones, probably connected with calendar keeping and with worship, and on a small scale in making daring operations on the skull. 4,000 years ago is given as a probable date for that early community in Kent, but evidences of Neolithic men occur in situations which demand a much greater antiquity, perhaps 30,000 years, and man was not young then. We must open one more chapter in the thrilling story of the Ascent of Man, the Metal Ages, which are, in a sense, still continuing. Metals began to be used in the late polished stone or Neolithic times, for there were always overlappings. Copper came first, bronze second, and iron last. The working of copper in the East has been traced back to the fourth millennium BC, and there was also a very ancient copper age in the New World. It need hardly be said that where copper is scarce, as in Britain, we cannot expect to find much trace of copper age. The ores of different metals seem to have been smelted together in an experimental way by many prehistoric metalurgists, and bronze was the alloy that rewarded the combination of tin with copper. There is evidence of a more or less definite bronze age in Egypt and Babylonia, Greece, and Europe. It is not clear why iron should not have been the earliest metal to be used by man, but the iron age dates from about the middle of the second millennium BC. From Egypt, the usage spread through the Mediterranean region to North Europe, or it may have been that discoveries made in central Europe, so rich in iron mines, saturated southwards, following, for instance, the root of the amber trade from the Baltic. Compared with stone, the metals afforded much greater possibilities of implements, instruments, and weapons, and their discovery and usage has undoubtedly great influence on the ascent of man. Occasionally, however, on his descent. Retrospect Looking backwards, we discern the following stages. One, the setting apart of a primate stock marked off from other mammals by a tendency to big brains, a free hand, gregariousness, and good humor talkativeness. Two, the divergence of marmosets and new world monkeys and old world monkeys, leaving a stock, an anthropoid stock, common to the present day and its stink to apes and to mankind. Three, from this common stock the anthropoid apes diverged, far from ignoble creatures, and a humanoid stock was set apart. Four, from the latter, we follow Sir Arthur Keith and other authorities, there arose what may be called without disparagement, tentative or experimental men, indicated by Pythocanthropus the erect, the Heidelberg man, the Neanderthalers, and best of all, the early men of the Sussex-wield, hinted at by the pilt-down skull. It matters little whether particular items are corroborated or disproved. For instance, whether the Heidelberg man came before or after the Neanderthalers, the general trend of evolution remains clear. Five, in any case the result was the evolution of Homo sapiens, the man we are, a quite different fellow from the Neanderthaler. Six, there arose various stocks of primitive men, proving everything and holding fast to that which is good. There were the Paleolithic peoples, with rude stone implements, a strong vigorous race, but probably, in most cases, supplanted by fresh experiments. These may have arisen as shoots from the growing point of the old race, or as a fresh offshoot from more generalized members at a lower level. This is the eternal possible victory alike of aristocracy and democracy. Seven, Paleolithic men were involved in the succession of four great ice ages or glaciations, and it may be that the human race owes much to the alteration of hard times and easy times, glacial and interglacial. When the ice fields cleared off, Neolithic man had his innings. Eight, and we have closed the story in the meantime with the metal ages. It seems not unfitting that we should, at this point, sound another note. That of the man of feeling. It is clear in William James's words, quote, bone of our bone and flesh of our flesh are these half-brutish, prehistoric brothers, girded about with the immense darkness of this mysterious universe even as we are. They were born and died, suffered and struggled. Given over to fearful crime and passion, plunged in the blackest ignorance, preyed upon by hideous and grotesque delusions, yet steadfastly serving the profoundest of ideals in their fixed faith, that existence in any form is better than non-existence, they ever rescued triumphantly from the jaws of ever imminent destruction, the torch of life, which, thanks to them, now lights the world for us. Races of Mankind Given a variable stock spreading over diverse territory, we expect to find it splitting up into varieties which may become steadied into races or incipient species. Thus we have races of hive bees, Italians, punyx and so forth, and thus there arose races of men. Certain types suited certain areas and periods of inbreeding tended to make the distinctive peculiarities of each incipient race well defined and stable. When the original peculiarities, say of Negro and Mongol, Australian and Caucasian, arose as brusque variations or mutations, then they would have had great staying power from generation to generation. They would not be readily swamped by intercrossing or averaged off. Peculiarities and changes of climate and surroundings, not to speak of other change-producing factors, would provoke new departures from age to age and so fresh racial ventures were made. Moreover, the occurrence of outbreeding when two races met, in peace or in war, would certainly serve to induce fresh starts. Very important in the evolution of human races must have been the alternating occurrence of periods of inbreeding, endogamy, tending to stability and sameness, and periods of outbreeding, exogamy, tending to changefulness and diversity. Thus we may distinguish several more or less clearly defined primitive races of mankind, notably the African, the Australian, the Mongolian, and the Caucasian. The woolly-haired African race includes the Negroes and the very primitive Bushmen. The wavy to curly-haired Australian race includes the jungle tribes of the Deccan, the Veda of Salon, the jungle folk or Samank, and the natives of unsettled parts of Australia, all sometimes slumped together as pre-Dravidians. The straight-haired Mongols include those of Tibet, Indochina, China, and Formosa, those of many oceanic islands, and of the north from Japan to Lapland. The Caucasians include Mediterranean, Semites, Nordics, Afghans, Alpines, and many more. There are very few corners of knowledge more difficult than that of the races of men, the chief reason being that there has been so much movement and migration in the course of the ages. One physical type is mingled with another, inducing strange amalgams and novelties. If we start with what might be called zoological races or strains, differing, for instance, in their hair, woolly-haired Africans, straight-haired Mongols, curly or wavy-haired pre-Dravidians, and Caucasians, we find these replaced by peoples who are mixtures of various races, brethren by civilization more than by blood. As Professor Flinders Petrie has said, is that of a group of human beings whose type has been unified by their rate of assimilation, exceeding the rate of change produced by the infiltration of foreign elements. It is probable, however, that the progress of precise anthropology will make it possible to distinguish the various racial strains to make up any people. For the human sense of race is so strong that it convinces us of reality, even when scientific definition is impossible. It was this the British sailor expressed in his answer to the question, what is a dago? Dagoes, he replied, is anything what isn't our sort of chaps. Steps in Human Evolution Real men arose, we believe, by variational uplifts of considerable magnitude, which led to big and complex brains and to the power of reasoned discourse. In some other lines of mammalian evolution there were, from time to time, great advances in the size and complexity of the brain, as is clear, for instance, in the case of horses and elephants. The same is true of birds as compared with reptiles, and everyone recognizes the high level of excellence that has been attained by their vocal powers. How these great cerebral advances came about we do not know, but it has been one of the main trends of animal evolution to improve the nervous system. Two suggestions may be made. First, the prolongation of the period of antenatal life in intimate physiological partnership with the mother may have made it practicable to start the higher mammal with a much better brain than in the lower orders, like insectivores and rodents, and still more more supials, where the period before birth, gestation, is short. Second, we know that the individual development of the brain is profoundly influenced by the internal secretions of certain ductless glands, notably the thyroid. When this organ is not functioning properly, the child's brain development is arrested. It may be that increased production of certain hormones, itself, of course, to be accounted for, may have stimulated brain development in man's remote ancestors. Given variability along the line of better brains, and given a process of discriminant sifting, which would consistently offer rewards to alertness and foresight, to kin's sympathy and parental care, there seems no great difficulty in imagining how man would evolve. We must not think of an Aristotle or a Newton, except as fine results which justify all the groaning and travelling. We must think of average men, of primitive peoples today, and of our forebears long ago. We must remember that much of man's advance is dependent on the external registration of the social heritage, not on the slowly changing ritual inheritance. Looking backwards it is impossible, we think, to fail to recognize progress. There is a ring of truth in the fine description Aeschylus gave of primitive men that, first beholding they beheld in vain, and hearing heard not, but, like shapes and dreams, mixed all things wildly down the tedious time, nor knew to build a house against the sun with wickeded sides, nor any woodwork new, but lived like silly ants beneath the ground, in hollow caves unsunned. There came to them no steadfast sun of water, nor of spring-flower perfumed, nor of summer full of fruit, but blindly and lawlessly they did all things. Contrast this picture with the position of man today. He has mastered the forces of nature and is learning to use their resources more and more economically. He has harnessed electricity to his chariot, and he has made the ether carry his signals. He taps supplies of material which seem for centuries unavailable, having learned, for instance, how to capture and utilize the free nitrogen of the air. With his telegraph and wireless, he has annihilated distance, and he has added to his navigable kingdom the depths of the sea and the heights of the air. He has conquered one disease after another, and the young science of heredity is showing him how to control in his domesticated animals and cultivated plants the nature of the generations yet unborn. With all his faults he has his ethical face set in the right direction. The main line of movement is towards the higher embodiment of the true, the beautiful, and the good in healthy lives which are increasingly a satisfaction in themselves. Factors in Human Progress Many, we believe, were the gains that rewarded the Arboreal Apprenticeship of man's ancestors. Many, likewise, were the results of leaving the trees and coming down to the solid earth, a transition which marked the emergence of more than tenetive men. What great steps followed! Some of the greatest were the working out of a spoken language and of external methods of registration, the invention of tools, the discovery of the use of fire, the utilization of iron and other metals, the taming of wild animals such as dog and sheep, horses and cattle, the cultivation of wild plants such as wheat and rice, and the irrigation of fields, all through the ages necessity has been the mother of invention and curiosity its father. But perhaps we miss the heart of the matter if we forget the importance of some leisure time. We're in to observe and think. If our earth had been so clouded that the stars were hidden from men's eyes, the whole history of our race would have been different. For it was through his leisure time observations of the stars that early man discovered the regularity of the year and got his fundamental impressions of the order of nature, on which all his science is founded. If we are to think clearly of the factors of human progress, we must recall the three great biological ideas, the living organism, its environment and its functioning. For man these mean, one, the living creature, the outcome of parents and ancestors, a fresh expression of a bodily and mental inheritance. Two, the surroundings, including climate and soil, the plants and animals these allow. And three, the activities of all sorts, occupations and habits, all the actions and reactions between man and his milieu. In short, we have to deal with folk, place, work, the familie, lieu, travail of the Laplace school. As to folk, human progress depends on intrinsic racial qualities, notably health and vigor of body, clearness and alertness of mind, and an indispensable sociality. The most powerful factors in the world are clear ideas in the minds of energetic men of good will, the differences in bodily and mental health which mark races and stocks within a people, just as they mark individuals, are themselves traceable back to germinal variations or mutations and to the kind of sifting to which the race or stock has been subjected. Easygoing conditions are not only without stimulus to new departures, they are without the sifting which progress demands. As to place, it is plain that different areas differ greatly in their material resources and in the availability of these. Moreover, even when abundant material resources are present, they will not make for much progress unless the climate is such that they can be readily utilized. Indeed, climate has been one of the great factors in civilization, here stimulating and their depressing energy, in one place favoring certain plants and animals important to man, in another place preventing their presence. Moreover, climate has slowly changed from age to age. As to work, the form of a civilization is in some measure dependent on the primary occupations, whether hunting or fishing, farming or shepherding, and on the industries of later ages which have a profound molding effect on the individual at least. We cannot however say more than that the factors of human progress have always had these three aspects, folk, place, work, and that if progress is to continue on stable lines it must always recognize the essential correlation of fitter folk in body and mind, improved habits and functions, alike in work and leisure, and bettered surroundings in the widest and deepest sense.