Part 1

POCKET SERIES NO. 467 Edited by E. Haldeman-Julius

Evolution Made Plain

John Mason

HALDEMAN-JULIUS COMPANY GIRARD, KANSAS

Copyright, 1923, Haldeman-Julius Company.

EVOLUTION MADE PLAIN

_The time has come when scientific truth must cease to be the property of the few--when it must be woven into the common life of the world.--Agassiz._

_Read not to contradict and confute, nor to believe and take for granted, * * * but to weigh and consider.--Bacon._

_The man who will not investigate both sides of a question is dishonest.--Abraham Lincoln._

_Intolerance is the product of an ignorant, primitive mind. We should tolerate anything of an intellectual nature except intolerance. Freedom of opinion is the root, flower and fruit of liberty--its very essence.--Anonymous._

WHAT EVOLUTION IS AND IS NOT

Addison said, “The real substance of a bulky volume can be condensed into a small pamphlet.”; and it is believed that the fundamental principles of a great scientific discovery like evolution can be outlined in a few pages, and in a way so plain and in words so simple that any one who is at all interested can get a fairly good understanding of its scope. With this idea in mind an attempt is here made to explain evolution, to tell what some of its laws are and how they work, and to present briefly some of the evidences that support the doctrine.

Contrary to popular belief evolution is not confined to the origin of man, but it explains how all living things have become as we now see them, and how and why the most of them are being changed. It teaches that all living species of plants and animals, including man, also the thousands of extinct species which have left their fossil records in stratified rocks, have been developed from a few small and simple forms--probably one, and that a mere cell. And it shows, too, that this has been done by the operation of natural laws, the same laws we see in operation today.

Evolution does not teach that every living thing is “day by day, in every way, growing better and better.” On the contrary, it shows that many species deteriorate, are driven to the wall and become extinct, while only the best fitted survive. For instance, of the twenty-five orders of reptiles in the Jurassic period--known to the geologists by their fossils--only five have come down to our times. But out of the reptilian orders, then the highest forms of living things, have come the superior orders of later times--birds and mammals. And this is evolution.

We sometimes hear the statement that scientists are not in agreement in regard to evolution. The point of disagreement is in respect to the part played by natural selection in the development of species, and not as to whether or not evolution is a fact. The discussion is in regard to the _how_ of the fact and not the fact itself. No great scientist since Agassiz, who died in 1873, has opposed evolution.

Neither does evolution teach that one species may develop into another, as that the goat may develop into the deer, or that the ape may evolve into man. For one species to become another existing species it would have to take the back track to the point where the two species began to diverge and travel the other route--which of course would be impossible. This may help in getting the idea: the larger divisions and groups of animals (fishes, reptiles, mammals, etc.) may be compared to the main or primary branches of a tree, the families and orders (as the deer, the cat, and the dog) to the secondary branches growing from the primary ones, and the species to the further divisions of the secondary branches. Now we can see that one species can no more become another--that is, any now existing--than one branch of a tree can become another. A species can, in time, if subject to the proper conditions, split into varieties which, if developed far enough, may become distinct species. But no one of these species can be said to have been evolved from a contemporary species, for all have been changed, and the stock from which they came has ceased to exist as such. Each of the existing species would have a distinct name such as, for instance, cow, bison, Cape buffalo, yak. Now suppose the fossil remains of the common ancestor of the above-named species were found--what should it be called, cow, bison, Cape buffalo, or yak? It would be neither, for it would probably differ as much or more from them as they differ among themselves. Thus is laid to rest the idea that evolution is a theory that man was evolved from, or by way of, the monkey or the ape. They are as distinct species as is man himself.

GEOLOGICAL EVIDENCES OF PROGRESSIVE DEVELOPMENT

All life on this globe is divided into two great classes, vegetable and animal. All animals belong to one or the other of two grand divisions: invertebrates (those without backbones) and vertebrates (the backboned). The latter class, comprising more than 30,000 known species, is subdivided into five great groups: fishes, frogs, reptiles, birds and mammals. At the top of the highest group, mammals (those which bring forth their young alive), is man. Birds and mammals were evolved from the reptiles--both offshoots of the same stock--and are contemporaneous in development and descent.

The various classes and groups of animals, both in the order of development from the simple to the complex and in the time of their arrival, are in the order named: first the small, one-celled animals (many species of which are found today) then more complex organisms of the invertebrate division, later the fishes, amphibians, reptiles, and mammals, including man.

The story told by the geologist is in perfect agreement with those laws of development which we call evolution. The lowest, simplest forms of life are the oldest as is shown by their fossil remains (bones, shells, etc.) found in stratified or water-laid rock. These fossils were deposited in sediment as it formed in sea and lake thousands and millions of years ago. In the movements of the earth’s crust the sediment of ancient sea and lake bottoms was raised above the water and became land, the sediment hardening into rock. All sediment is formed on a level, but in its up-heaval--generally slow, sometimes violent--it is often tilted at various angles exposing its edges. It is from this out-cropping, stratified rock (the sum of which is often several miles in depth) that forms the outer part of the earth’s crust that the geologist reads the story of creation.

The oldest or lowest water-laid rock is the archaean in which there are no fossils. Above this, in the stratum formed in a later period are found evidences of the beginnings of life. After millions of years of growth and development the shell fish, at the top of the invertebrate group, is produced. Then comes a period of uncounted millions of years in which the fishes, the lowest of the vertebrates, are being developed--millions of years to bridge the chasm between the two main divisions of the animal kingdom; millions of years to produce a backbone! Other long periods of time, filled with change and development, come and go--the age of the coal plant and of the frogs, succeeded by the age of reptiles, giant monsters, cold-blooded and of small brain, swarming sea and land. Long ages pass; the reptilian monsters have become extinct, leaving as their representatives only a few dwarfed species--the crocodile, the lizard, the snake, the turtle. Of mammals the lowest orders arrive first, followed by the more highly developed until finally man appears.

Naturally, fossils of land animals are few compared with those of marine animals. Practically all the remains of the latter sank and were covered with the slowly accumulating sediment, while the bones of the former only rarely were swept out to sea and lake. Rarest of all fossils are those of man. A few have been found antedating history by several thousand years, but we get a far more complete knowledge of our primitive ancestors from the tools and weapons that they left in sediment and drift before the dawn of the present era. We can trace his progress upward through all degrees of culture from the rude old stone age of a hundred thousand years ago, through the new stone age, the copper and bronze age, and the iron age to the beginning of written records.

Yet, so old is our planet and so long ago since life dawned on it--so long even since the first mammals appeared--that man’s arrival a hundred-or-so thousand years ago is but as yesterday. To paraphrase an illustration by Slade and Ferguson: “Suppose we take the earth as 365 million years old, and consider this period as a year, one million years being taken as a day.” Then, on this scale the vertebrates came into existence late in the summer or early fall, the mammals not earlier than the end of November, and “the whole period of man is not likely to have been further back than the evening of December 31st, and the earliest historic evidence (in Egypt) is not more than ten minutes before the last midnight.”--“the last midnight,” of course, being the present.

EVIDENCES OF EVOLUTION

Of the many evidences of the kinship of all animals including man only a few can be mentioned in this book. All animals, man included, are constructed on the same general plan. They have the same organs--brain, heart, lungs, digestive tract, nerves, skin--performing the same functions for the same purposes. The skeleton of man can be compared, bone for bone, with that of a monkey, bat or seal. The bat’s membranous wing is ribbed with bones corresponding to the bones of a monkey’s or a man’s hand. The wing of both the bat and the bird has one bone from the shoulder to the first joint, and two bones from the first to the second joint, like the fore leg of quadrupeds and the arm of man--thus proving that the fore leg, the arm and the wing are only modifications of the same limb. The biped bird and biped man are modified quadrupeds.

All the five hundred muscles of the human body correspond with the muscles of other mammals. Even the brain, wherein man differs most from the lower animals, has the same chief fissures and folds in both man and the animal nearest man, the orang-outang. Man and the other animals have the same five senses and the same sense organs. They in common have the same basic emotions, such as surprise, jealousy, pride, hatred, shame, anger, grief, affection, and a sense of the ludicrous. Bucks says, “So is man’s so-called human mind rooted in the senses and the instincts of all his ancestral species; and not only so, but these senses and instincts still live in him, making up, indeed, far the larger part of his current everyday life; while his higher psychical life is merely the outgrowth and flower of them.”

The old formula was: “Man is governed by reason; brutes by instinct.” But science has proved that lower animals are not guided altogether by instinct, that many of their actions are the results of mental activities remarkably similar to reasoning. On the other hand man himself has instinct--and well for him that he has, for his reason, as yet, is only partially developed. If we will but subtract from the sum of man’s actions, not only those prompted by instinct, but those also that result from habit, custom, prejudice, and the emotions of anger, revenge, vanity, and other elemental passions, we will not feel like crying from the housetops that “man is governed by reason.”

Man and the lower animals have similar diseases. He is liable to contract from, or communicate to them, such diseases as glanders, hydrophobia, cholera, tuberculosis. Drugs, tobacco and alcohol have the same effects on animals as on us.

Of course the dog, the ape, the horse and man do not perfectly agree in their corresponding parts and in their natures--if they did they would belong to the same species--but their similarities are so remarkable that they have a profound meaning for the thoughtful, however meaningless they may be to the thoughtless and the prejudiced.

In embryonic development are found evidences not only of man’s close relationship with all animals but of the long, long route he and they have travelled in their common descent from the simpler forms of life. Darwin says that the whole process of reproduction, from the first act of courtship by the male to the birth and nurturing of the young, is very much the same in all mammals.

The lowest forms of animal life, the one-celled animals, are without sex, and multiply by dividing into half, each half developing into a complete cell, which in turn is subjected to the same dividing process. Many species of these lowly organisms still exist, never having developed further than the unicellular stage. All higher forms, as of fishes, reptiles, birds, mammals, begin life at this point--as a single cell. The cell, germ, or ovum of an embryo (the young of a mammal before birth) when fertilized divides, forming two cells, the two divide into four, the four into eight, and so on, until there is a colony of similar cells enmassed, and with a little rod of tissue--the beginnings of the spinal column--running through. The embryo at this stage is passing beyond the lowest grand division, the invertebrates. Entering the vertebrate division the embryo passes into the fish group. Deep grooves, gill slits, appear on the side of the neck of the embryo and six pairs of arched branches of arteries arise, just as in fishes, as if to give blood to the gills. Later all but one of these pairs disappear. The arms and legs of the child, like the legs of all other embryos, begin to develop, and continue to do so for some time, on the same plan as the fins of fishes.

Further along in its development the embryo assumes all the characteristics of the quadruped even to the tail which in the human embryo at this stage is longer than its legs. During the sixth month the entire body of the human foetus, except the palms and soles, is covered with fine, woolly hair.

Thus far the human embryo has developed in the same way, has undergone the same changes, has passed through precisely the same stages as the embryo of other animals. In its further development it leaves them all behind except those nearest man. Its tail disappears, and it now has an opposable or thumb-like great toe which with the monkey and the ape is a permanent characteristic. It is only in the latest stages of development that the human embryo presents marked differences from the embryonic ape.

Of the fact that the embryo in its development from a single fertilized cell passes through all the stages representative of the principal animal divisions, and in a progressive order from the simple to the complex and highly developed, there is no explanation but that of heredity and descent--of descent of the higher animals from the lower with heredity transmitting the records of the remote ancestral stages. Each stage, as of the fish, the quadruped, the ape, is a sign board along the route of man’s descent. The nine months’ embryonic period of each of us is an epitome of the history of the race down to the human period.

Nor do the evidences of race-history as revealed by the child cease with its birth. The babe is nearer the lower mammals than is the adult man. When it acquires the use of its limbs it begins life as a quadruped. Its blundering attempts in learning to stand erect and walk is evidence of the fact that man’s peculiar mode of locomotion is a late acquirement. Like the lower animals the babe makes known its wants by means of natural language; it later acquires artificial or spoken language in the same slow, laborious way that it was acquired by the race. At the average age of three years the child has become self-conscious; his mind has passed the mental stage of all animals below man. Psychically he has become man.

In certain periods of youth the child is a tree-climber, a cave-digger, childish sports that hark back to periods passed through hundreds of thousands of years ago in the childhood of the race. At a certain stage his emotional nature has developed to the point that he is conscious of wrong-doing. This is what the old theologians called “the age of accountability.” If there is a grain of truth in the chaff-heap of Mosaic mythology the fall of Adam indicates the point in the development of the race when conscience had dawned and feelings of remorse had begun to stir within. Man had reached the age of accountability. But prior to the “fall” there was a rise.

Rudiments or vestiges are also evidences of the descent (or ascent) of the higher forms of life from the lower. Rudiments are incomplete parts of the body which have become arrested in their development, and which are now of no use, nor would now be of use if fully developed. They are relics handed down to us by the laws of heredity from a long-past age when they were well developed and useful to our lowly ancestors. Though we outgrow primitive conditions and stages of development we can not get rid of the past, but must drag it around with us as the snail drags its shell.

All the higher animals bear within their bodies the reminders of a humble origin, some of which are: The incisor teeth of certain grass-eating animals, so rudimentary as never to cut through; the small hoof points of the cow which do not touch the ground, and the rudimentary fifth and sixth teats on the hinder part of her udder; the splint bones in the horse’s leg--vestiges of toes when he was a three-toed animal; the scanty, downy hair that covers the human body.

Certain muscles by which animals can twitch the skin are inherited by some persons who can move the scalp and the ears. The sense of smell in civilized man has become almost rudimentary. The vermiform appendix is not only useless but often injurious. It points back to the time when our ancestors were strict vegetarians--grass-eaters. In the _os coccyx_ man carries about with him the rudimentary bones of a tail. This, with the fact that the human embryo at one stage has a tail longer than its legs, is Nature’s everlasting reminder that proud man’s remote ancestor was adorned with a tail.

In order to get as clear an idea as possible of man’s exact place in the animal scale we should note the points wherein man differs from his nearest relatives--the orang, the gorilla, the chimpanzee, the gibbon--as well as the points wherein he agrees with them. Here are the most obvious points of dissimilarity. Man walks erect, though in his first year he goes on all fours, while apes only occasionally walk, and that in a semi-erect position, their arms, longer than their legs, reaching the ground, knuckles touching. The nose of the ape is small, undeveloped; the canine teeth are very large; the mouth projects, and there is no chin. The entire body except the palms and soles is covered with hair. The brain capacity of the ape is less than half that of man.

On the other hand there are more points of similarity than of dissimilarity between man and the apes; and if the points wherein they differ be examined they will be found to be differences in degree rather than in kind. The higher apes are entirely without tails; the embryo of the ape, like the human foetus, loses its tail sometime before birth. The young ape (monkey also) is born in almost as helpless a condition as is the human babe. The female ape has two mammary glands (udders) and they are always on the chest. Adult apes have the same teeth as man--thirty-two in number, incisors, canines, premolars, molars. They have the same 200 bones, the same 500 muscles, the same organs and glands. On their toes and fingers they have flat nails, like man, instead of claws. On account of the ape’s opposable great toe they were formerly classed as four-handed; but this was an error. In all essential respects their legs terminate in feet. Like man they are bipeds, and like man they have two hands. The brain of the ape, though much smaller than man’s, as we would expect it to be, is constructed on the same general plan as his with the same main fissures and the same groups of cells. There is no “missing link” in the plan and structure of man’s brain, whatever difference there may be between his and the ape’s in capacity.

No scientist has ever been so foolish as to say that man and the apes belong to the same species. There are four species of the higher apes and one of man, though the one species of man is divided into five varieties, called “races.” Varieties differ less widely than species. Individuals within a variety also differ. Differences are no bar to unity if they are nullified and outweighed by similarities.

Finally, let us keep in mind that while man has departed from the ancestral type, developing in one direction, the apes have gone off in another and have acquired characteristics peculiarly their own. Resemblance in a babe and a young ape is far greater than in a man and an adult ape. The same is true of the young of all allied species. This divergence from birth of the adults of different species is strong evidence of a common origin.

These are only a few of the hundreds of evidences proving that man fits into the same creative scheme with the lower animals--proving that he, in common with them, has developed from still lower forms, and that, as a product of the creative forces of Nature, he is wholly subject to her laws.

CONNECTING LINKS

There is a greater unity of all life than the many divisions and sub-divisions of the analyst would seem to warrant. The dividing lines between the different classes, orders, families and species are more apparent than real, the barriers of separation not so impassable as appear at first sight.

To begin at the bottom, there is no hard and fast line drawn between living and non-living matter--or at least it is not always easy to say where the line should be drawn. Tyndall says, “The tendency of modern science is to break down the wall of partition between the organic and the inorganic, and to reduce both to the operation of forces which are the same in kind, but which are differently compounded.”

Passing on to the first grand division of life, it would seem that nothing could be plainer than the line of cleavage between vegetable and animal life. Yet there is a twilight zone between the two where each shades off toward the other, and which is inhabited by several living species of so doubtful a nature that scientists cannot agree as to which of the two great kingdoms they belong. These doubtful organisms are claimed by both the botanist and the geologist and are described in the textbooks of both. Really they do not belong to either division, but are simply organisms that have not risen in the scale of life to the diverging point of the animal and vegetable kingdoms.