# Creation by Evolution/Cumulative Evidence for Evolution

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CUMULATIVE EVIDENCE FOR EVOLUTION
By Horatio Hackett Newman
Professor of Zoölogy in the University of Chicago
No greater mistake about evolution could well be made than to limit its application to living organisms. There has undoubtedly been as real an evolution of the Cosmos, of the solar systems, of the earth and other planets, of the molecules, and of the atoms as there has been of organisms. All of these have much in common. In none of them is there any fixity or stability; in all of them there is rhythmic and orderly change. In none of them does the course of change proceed steadily in one direction. On the contrary, it commonly seems to proceed from states of less complexity to states of greater complexity and then to revert to states of less complexity. For example, according to the latest theory, a sun such as our own—and there are hundreds of millions of these in our own galaxy alone—is believed to have had many vicissitudes during its lifetime of quintillions of years. In the course of its wanderings through space it may come relatively close to another passing sun and during this passage give birth to a family of planets, each of which is its child. As one would expect of a sun’s child, each planet has a long period of growth, a period that lasts for billions of years. Sooner or later, however, our sin may come again within the gravitational reach of another sun, the calculated average interval between such approaches being, in round numbers, a billion times a billion years. When this happens, the first family of ​planets will be broken up and another one born. This rhythm may go on forever, so far as we can tell, for there appear to be no agencies tending to put an end to it.
Each star or sun, apart from these incidents associated with the origin and evolution of planets, has a long, slow evolution of its own. Each is at first a young son, very tenuous, relatively cool, and blue-white in color. As it grows older it becomes hotter, denser, and yellowish in color. With increasing age it becomes progressively denser and cooler and changes in color from lighter to darker red. With this progressive increase in density the constitution of its atmosphere undergoes remarkable changes. In the young suns the atmosphere consists of numerous lighter elements and compounds that can exist at relatively low temperatures; in the somewhat older suns, which are intensely hot, the atmosphere contains only the lightest and simplest atoms, such as hydrogen and helium; in the old, red suns the atmosphere includes not only atoms of the heavier elements, but various compounds. The density of some of these aged suns is amazing. Astrophysicists estimate that a cupful of material from one of these old red suns, if weighed on the surface of our earth, would scale twenty-five tons.
A sun endures so long and changes so slowly that an ephemeral being like a man can observe no change in it. We know, however, that our own galaxy is made up of suns of all grades of brightness and density, and we therefore infer that suns have a regular course of existence—an evolution. Our own particular sun is middle-aged, verging on senility. To an observer living on a planet in another solar system it would appear as a reddish-yellow star, relatively a dwarf as compared with many of the giant suns in our galaxy.
A sun is at all times giving off enormous amounts of energy. This activity alone would cause it to change pro​gressively and continuously. All the evidence in our possession indicates that, apart from occasional relativly sudden, more or less accidental short cuts, the course of solar evolution is almost inconceivably slow.
Passing from suns to lesser material units, let us consider the evolution of planets. The lifetime of a planet as compared with that of a sun is short, and its evolution is correspondingly much more rapid, so rapid that many of the events of its career can be noted by man. In our own planet, for example, we have observed changes in the levels of continents, changes due to earthquakes, floods, and the vicissitudes of climate. Similar but far more extensive changes are recorded accurately in the strata of the earth’s crust.
An intelligent perusal of the rocky pages of our earth’s historical record shows that the hills are not eternal but are periodically coming into being and passing away; that the oceans change their depths and contours; that the continents join hands for a time and then part company; that parts of the continents become islands and that islands become attached to continents. If viewed by a being whose time passes as slowly as it passes for the sun, the earth would appear to be in a continual state of flux. It would seem to pulsate like a gigantic heart as the continental and oceanic areas periodically expand and contract. During the periods of relatively expanded continents and contracted seas the lands in many regions are high and mountainous. These high lands and mountains undergo a long, slow period of gradation, during which much of their solid material is washed into the sea. The filling up of the sea helps to make it overflow upon the lowest parts of the continents, and thus the area of the oceans increases and that of the continents decreases. Before this goes very far the increased weight of the sea floor and the lessened weight of the continents brings about another squeez​ing up of the continental blocks and a sinking of the sea-levels, and a new pulse beat of the earth takes place.
When the continents are extensive and high the climates are zonal—that is, there are zones of different climates in different regions. The climate is cold at the poles, warm at the equator, arid in central regions, and moist along coasts. When the continents are contracted and worn down low the climate is non-zonal and equable, the conditions of life are easy, and evolution is relatively slow. The rocky strata of earth’s crust show clearly that there have been several great continental pulse beats. A section of the walls of the Grand Canyon, for example, affords an opportunity to read the book of geology at a place where the earth has herself turned back the pages. To one who has learned to read the language in which it is written, nothing could be more certain than the story thus revealed. It is a true story, unspoiled and unedited by the hand of man. Those who have become experts in reading the record of the rocks agree in the interpretation of its pages, at least as to its main plot. About some minor details different versions are offered. It is clear, however, that since the earth reached its present diameter, at least a billion years ago, there have been no less than half a dozen major pulse beats of the earth; and numerous minor rhythmic changes have been superimposed upon the major rhythm. It is also certain, as shown by fossils, that the earth has been the abode of life during numerous physical and climatic changes of far-reaching extent and of great severity.
Leaving now the exceedingly large units of the universe, let us put on our shrinking caps and magically pass to the exceedingly small world of the atom. Modern physicists have revealed to us that the atom, once thought to be the smallest thing in existence, is really much like a miniature ​solar system, composed of a central relatively massive body around which revolve one or more planetary bodies, each occupying perhaps only about a millionth part of the space occupied by the smallest atom. An atom of hydrogen is the simplest atomic system known. It is composed of but one proton, or positively charged central particle, and but one electron, or negatively charged particle, which revolves in an orbit about it. The speed of the revolution of the electron is so tremendously great that it is practically everywhere at once within its orbit. The distance between the proton and the electron seems so enormous as compared with the minute size of these particles that one is forced to the conclusion that the inside of the atom is mainly empty space. One may get a more concrete idea of the relative sizes and distances within the atom by comparing the atom of hydrogen with the earth and the sun. It may be said, speaking broadly, that if the orbit of the electron about the proton in an atom of hydrogen were enlarged to the size of the orbit of the earth about the sun the electron would have a diameter about equal to that of the sun and the proton a diameter about equal to that of the earth. This somewhat topsy-turvy relation is due to the fact that the proton, though ever so much smaller than the electron, is nearly two thousand times as massive, or heavy.
Other atoms are far more complex than the hydrogen atom, some of them containing over two hundred times as many protons and electrons. No matter how large and complex an atom becomes, it includes no other kinds of particles than those contained in the simplest atom. All differences in the properties of elements are due to the number of and the variations in the arrangement and configuration of these ultimate particles. The nucleus of any other atom than that of hydrogen is composed of both protons and electrons, firmly organized into a relatively stable core, around which ​revolve a few or many planetary electrons in one, two or several shells, each capable of housing a definite number. Only the electrons in the outermost shell determine the chemical characteristics of the various atoms of the elements.
Some of the most complex atoms, such as those of uranium, thorium, and radium, are radioactive; that is, there is a sort of unrest in the nucleus which operates to break down the equilibrium existing among the protons and electrons and results in the shooting off, at tremendous velocity, of electrons and of groups of protons and electrons from the nucleus. The so-called Alpha rays given off by radioactive substances are composed of particles identical with the stripped nuclei of the helium atom, one of the lightest and simplest atoms. The emission of these rays is nothing more or less than a process of evolution of elements, one element becoming transformed into another. By radioactive disintegration the most complex elements, such as uranium, thorium, and radium, are reduced slowly and by distinct steps to elements of less complexity and greater stability. Thus when an atom of radium loses one Alpha particle it is reduced to radon, an extremely inert gaseous element. Radon goes over by another step into polonium and lead, and radioactive lead, by a further change involving the capture of another electron, becomes the element bismuth.
Physicists are just at the beginning of their program of transforming the elements or atoms into one another, and doubtless their future research will disclose many startling transformation. The evidence so far available points to the conclusion that what we once considered the most fixed, the most immutable units of the universe are far from stable—they are undergoing orderly transmutation from more complex to simpler forms. The transmutation seems very slow to us, but expressed in terms of cosmic time it is really rapid.
​The question naturally arises whether this process of atomic degradation is a one-way process, destined in the end to reduce all matter to its simplest form. The most recent discoveries of physicists seem to answer this question in the negative. There is a well-defined belief among experts in these matters that processes the reverse of those described above, involving a synthesis of simpler forms of matter into more complex, are going on out in the remotest interstellar spaces. Professor Millikan has detected vibrations emanating from these outer spaces—vibrations whose frequency is not even approached by any known earthly or solar phenomena—that are interpreted as evidences of immensely energetic synthetic processes involving the return of matter from its state of ultimate disintegration to conditions of integration and complexity. These observations seem to indicate that atomic evolution, like other phases of evolution, is rhythmic and orderly. Such a rhythm would seem to have no beginning and no ending. Perhaps our ideas of beginnings and endings are due merely to the limited functioning of our human brain mechanism.
In the hands of the expert the spectroscope is seemingly a magical instrument. By its help he can reach out and measure the distances and the diameters of the remotest stars, and even of the outer galaxies; he can use it as a long-range thermometer with which he can read the temperatures of the most distant suns; with it as a speedometer he can calculate the velocity of any of the heavenly bodies; and by its aid he can determine the chemical composition of the external parts of the suns almost as accurately as if he had them in his laboratory.
Spectroscopic analysis indicates that there is an orderly and systematic progression in the temperature and composition of the suns from the giants, or young suns, to the dwarfs, ​or old suns. Along with these evolutionary changes in the general character of the individual sun there is a parallel evolution of the elements. Thus it appears that evolution in the most minute units is definitely linked with evolution in the largest units. One evolution is obviously causally related to the other.
This conclusion leads me to venture upon the bolder statement that all evolution is in the end one vast universal coördinated process. We may be able to view one or two of its various aspects as though they were set apart from the rest, but any adequate study of one phase of evolution sooner or later leads to the conviction that it cannot be understood as a self-contained process or mechanism but can be made intelligible only by considering its relation to other processes or mechanisms. In the end we are inevitably driven to the conclusion that all nature is an organized system and that whatever happens in one realm is related to all other realms, and thus to the whole. Such a view as this leaves one with a feeling of awe in the presence of that vast unity we call Nature. There is room here, if anywhere, for a scientific concept of Deity, a central immanent power back of all these coördinated activities, from the smallest to the greatest.
If, as the astronomers, physicists, and chemists tell us, all lifeless nature is engaged in a ceaseless swing of intense activities; if the sun is growing older and changing its character with every succeeding day; if the earth has had its ups and downs, with numerous radical changes of climate; if, as the rocks tell us, life originated prior to a long series of these great environmental upheavals, it is indeed difficult to believe that living organisms, the most plastic of all natural units, should have remained fixed amidst the vast flux of world changes. In fact, there is between the records of geologic ​change and those of biologic change the closest parallelism. Whenever the rocks tell us a story of sudden continental uplift, with its associated climatic changes and stormy times, we find a corresponding adaptive change in the organisms preserved in the rocks. Whether the organisms respond directly to the changes in environment, or whether there is merely a change in standards of survival and an elimination of the less adaptable forms, we do not certainly know. Nothing could be clearer, however, than that there is a causal relation between organic and inorganic rhythms. Thus once more the unity of the whole process is impressed upon our minds. Organic evolution must be viewed not as an isolated process, but as an integral part of a vast system of orderly change.
No one line of evidence of organic evolution can possibly be conclusive in itself, though to the expert in each field his own data seem to need no outside support. The real proof of the validity of the concept of evolution lies in the fact that all lines of evidence point in exactly the same direction and are fully consistent with and corroborative of one another. Not only is this so, but each kind of evidence throws light upon all the other kinds. The obscure spots in one field are illuminated by facts derived from other fields. Thus the proof of organic evolution is cumulative. Before Charles Darwin recorded the results of his epoch-making work the known facts supporting the theory of evolution were few and unorganized. It is to the everlasting credit of Darwin that he amassed and organized so large and conclusive a body of evidence of evolution that he practically established the validity of the theory single handed.
The real test of the value of a theory, however, is not that it explains and rationalizes only the particular body of data it was devised to explain. It would be a poor theory that ​did not agree with the facts upon which it was based. A good theory must meet and explain all new facts within the scope of its applicability that come to light subsequent to its proposal. Since Darwin's Origin of Species was published ten times as many new facts about organic nature have been discovered as were known to Darwin. One after another new and radical discoveries that involve profound alterations in our fundamental views of life have been made, but none of them have in any way shaken our confidence in the theory of evolution. Had any new discovery in the least weakened or run counter to that theory its ever-watchful enemies would have pounced upon the discovery and exploited it to the fullest extent. But no discovery since Darwin's time has done other than strengthen and confirm the theory. The more specialized a branch of biology becomes, the more useful and necessary is the concept of evolution. Those that are most expert in the advanced and technical branches of biology are the most ardent advocates of evolution, for their data demand an evolutionary interpretation.
The evidences of evolution have been piled up year after year until their sheer mass now overwhelms all intelligent opposition. One who exposes himself open-mindedly to the evidences can no longer believe in a static world inhabited by fixed and unchanging species.
If evolution were a false doctrine, it should be easy to refute it by bringing forward facts that would contradict it. From time to time facts or alleged facts supposed to conflict with the principle of evolution have been brought forward by those who sought to overthrow it. Invariably, however, a more exhaustive study by trained scientists has shown that not only are the facts cited not contrary to evolution, but that they tend strongly to confirm it. To-day no adequately ​studied facts are out of accord with the theory of evolution, and thousands upon thousands proclaim its truth. What more cogent proof of a theory can one ask?
An excellent example of the way in which unexpected discoveries in a new field have supported and confirmed the theory of evolution is seen in the new science of serology, or blood tests. Before anything was known about the specific chemical constitution of the blood, animals had been classified into phyla, classes, orders, families, genera, and species. The method used was the method of homology—that is, groups of animals that were most nearly similar in structural pattern, not only in the adult form but throughout the course of embryonic development, were believed to be most closely related and were placed in the same species. Animals differing in details but having the same general features were placed in the same genus, family, order, class, phylum, according to the degrees of their structural resemblance. A comprehensive system of classification has thus been built up that is believed to constitute a sort of pedigree, or ancestral tree, of animal life.
A decade or so ago an entirely new and highly refined method, quite unrelated to the method of homology, was devised for testing animal relationships. This is the so-called blood precipitation method, which depends upon the fact that the blood of an animal is a sort of quintessence of its chemical composition. Thus the blood of all human beings has a highly specific chemical constitution differing from that of all other species. The same is true of the blood of the dog, the horse, or any other animal. The degree of chemical resemblance and difference in the blood of different animals may be measured quantitatively with the greatest accuracy. Assuming, then, that the degree of chemical resemblance ​in the blood of different animals will indicate the closeness of their genetic relationship, we should be able to classify the whole animal kingdom by means of resemblance in blood.
The technique involved may be elucidated by a single example. If we wish to find out the degree of kinship of man to any kind of lower animal, we proceed as follows: From a quantity of human blood we draw off only the clear, colorless serum. This we inject at intervals into the veins of a rabbit, for example. In time the rabbit’s blood becomes charged with a specific antibody for human blood and the serum from the blood is known as anti-human serum. This rabbit serum thus produced can now be used as a chemical reagent for testing the affinities of any other blood to human blood. If a few drops of it are placed in a test tube full of human serum a heavy white precipitate is immediately formed. If placed in the serum of a gorilla or of a chimpanzee a definite precipitate is formed, but it is less abundant and it forms more slowly than if human serum is used. No other species tried gives so positive a reaction with anti-human serum; but the baboons, the New World monkeys, the marmosets, and the lemurs (all Primates) react less and less readily in the order mentioned. All Primates show a stronger affinity than any other mammals for human blood, but if larger amounts of the reagent are used and more time is allowed from the reaction, the degree of affinity between man and all other mammals may be shown. Moreover, the order of closeness of relationship corresponds to that already worked out by the method of homology.
Most of the larger groups of animals have been investigated by this method and the most significant relationships determined are the following:
1. The birds show close relationship to the reptiles.
​2. The king crab, Limulus, is more closely related to scorpions and spiders than to any true crabs.
3. The whales, whose affinities among mammals have long been a problem, show an unmistakable affinity to the hoofed mammals, especially to the swine.
4. All Primates show closer affinity to one another than to any other mammals.
5. Similarly, all Carnivora are more like one another in blood than they are like other mammals.
When the system of classification based upon blood tests is compared with that based upon homologies it is found that the two corroborate each other in all essential respects. Where the method of homology had left the affinities of an animal somewhat doubtful, the blood test has been a valuable check upon earlier findings. Some relationships that were only doubtfully hinted at by homology have been definitely confirmed by blood tests.
One of the most conclusive evidences of the essential truth of the concept of evolution is that two utterly different methods of testing the relationships of animals should thus be in close agreement. If the blood-test method had given a different set of relationships than those indicated by homology we should doubtless have lost confidence in the validity of one or both methods, and our confidence in the principle of evolution would be to some extent shaken. To the same degree, then, that a disagreement in the results of the two methods would have weakened our confidence in evolution should not the close agreement of the two methods strengthen our confidence in it?
Another example of the way in which the evidences from diverse fields of science converge upon one conclusion, and only one, is to be found in the relationship of birds and reptiles. Studies of the comparative anatomy of adult birds ​long ago led to the belief that birds and reptiles have more in common than any other two classes of vertebrates. A study of comparative anatomy alone shows that birds are, as has been said, little more than “glorified reptiles,” differing from other reptiles mainly in the possession of feathers and wings. Blood precipitation tests support this conclusion; the blood chemistry of the two classes indicates that they are closely related. Embryology reveals the fact that birds, long before they are hatched, have the beginnings of typically reptilian teeth, which never reach maturity. The eggs, embryonic membranes, and indeed the whole course of the embryonic history of birds, is strikingly reptilian. In fact, it is only in later stages of embryonic development that the true avian characters begin to appear. The most characteristically avian feature of a bird consists of its feathers; but even these show by their development that they are no more than finely subdivided reptilian scales.
If, then, birds are specialized descendants of reptiles, it is obvious that there must have been transitional stages leading from reptiles to birds; and it is just here that palaeontology furnishes the evidence that settles the question. In a deposit of Bavarian shale there have been found two nearly complete and well-preserved fossil specimens of a kind of animal that is hard to classify as either reptile or bird, for it obviously possesses some of the features of both. This extinct animal, which is known as Archaeopteryx, is an animal half-way between a reptile and a bird. It had true feathers and it had fore limbs that are half wings and half fore legs, each having three long, prehensile fingers. It had a long, slender lizard-like tail, on which there was a lateral fringe of large feathers. The head was essentially reptilian, having no horny beak but a full set of reptilian teeth. What better evidence could one wish that the birds have been derived from ​reptilian ancestors? Is it even remotely probable that the story of evolution told independently by all these natural records is false? Nature does not lie. Here, as elsewhere, several of nature’s witnesses tell the same consistent, straight story, presenting cumulative evidence that cannot be refuted.
Biology furnishes many examples of the convergence of evidence upon a common conclusion. Only a sample or two have been offered to illustrate the fact that the proof of evolution, though somewhat indirect, is conclusive. It is the sheer mass of converging and cumulative evidence that in the end wins the day for evolution.
Though most of the evidences may be called indirect, this word cannot be applied to the evidence derived from genetics in the study of evolution going on to-day. The modern geneticist breeds under observation and control huge populations of rapidly breeding animals and plants. Under his very eyes there come into being scores and hundreds of new or changed types of individuals that pass their peculiarities on to their progeny according to definite laws of inheritance. Most of the changed types (mutants) are inferior in various ways to the typical individuals of the species. Some mutants are so weak or defective that they die young and leave no offspring. Occasionally, however, a mutant appears that possesses a new character or set of characters that constitutes an improvement. Such a new character persists and becomes incorporated in the hereditary complex of the species. Evolution can thus be seen to proceed by the production of large and small hereditary variations and the persistence through heredity of the good or relatively harmless mutations.
If a species becomes geographically separated into two groups, these groups tend gradually to diverge more and more. There are at least two reasons for this divergence: first, a group of individuals that becomes isolated from the ​main body of its species will tend to form a local race characterized by racial differences; second, if the environments of two groups thus separated are different, the standard of survival will be different, not only for the older characters but for the ever-recurring mutations as well. In the course of time these divergent forces inevitably create distinct species.
In his studies of contemporary life the geneticist has actually observed the process of evolution in operation. The processes observable to-day, if projected into the past, would be adequate to account for the evolution that has taken place in the past. Science had taught us that the present and the past are one; if we can analyze the present we have the key to the past and to the future. Evolution is obviously going on to-day. What better proof than this do we need for our belief that evolution has gone on in the past?
In conclusion let us say that the principle of evolution is so well established by the amassed evidence derived from every field of science that it has come to be regarded in scientific circles as one of the great laws of nature, ranking with the law of gravitation in scope and validity. And now a word for the theologian: Evolution no more takes God out of the universe than does gravitation. Both these great principles are mere manifestations of the grand strategy of Nature. They indicate the methods used by the ruling power back of the universe. The theory of evolution, as has often been said, does not deny creation; it merely explains the method of creation.
REFERENCES
* Lull, R. S. Organic Evolution. The Macmillan Co., 1917.
* Lull, R. S. and others. The Evolution of the Earth and its Inhabitants. Yale Univ. Press, 1918.
* Newman, H. H. Evolution, Genetics, and Eugenics (2nd ed.). The University of Chicago Press, 1925. ​
* Newman, H. H. The Gist of Evolution. The Macmillan Co., 1926.
* Newman, H. H. and others. The Nature of the World and of Man. The University of Chicago Press, 1926.
* Scott, W. B. The Theory of Organic Evolution. The Macmillan Co., 1917.
“The purpose of science is to develop, without prejudice or preconception of any kind, a knowledge of the facts, the laws and the processes of nature. The even more important task of religion, on the other hand, is to develop the consciences, the ideals and the aspirations of mankind. Each of these two activities represents a deep and vital function of the soul of man, and both are necessary for the life, the progress and the happiness of the human race.
“It is a sublime conception of God which is furnished by science, and one wholly consonant with the highest ideals of religion, when it represents Him as revealing Himself through countless ages in the development of the earth as an abode for man and in the age-long inbreathing of life into its constituent matter, culminating in man with his spiritual nature and all his Godlike powers.”—Dr. Robert A. Milliken, in Science.