The following lessons, while they do not treat directly of either the chemistry of food or the chemistry of the body, are so closely allied to these subjects that this work would not be complete without them.

What Is Evolution?

If a resident of a city, who is not familiar with modern farm machinery, should see a grain-binder at work, he would be impressed with the skill and the ingenuity of man. In all probability he would think that the machine was the product of one inventive mind. In this, however, he would be mistaken. The reaper in its modern form is the result of gradual development or growth.

The earliest method of gathering grain was pulling it up by the roots. Later, as cutting tools were invented, a rough knife was used to sever the stalks just above the ground. An improvement upon this method was the cycle; then came the scythe, then the cradle; and next came the mower which was operated by horse-power. From the mower was developed the self rake, which bunched the grain so that the hand-binders could work with greater facility. The next improvement was a self-binding machine. In the present machine we have all of these and many other improvements, which give greater speed with less waste of labor and time.

This development of the grain-binder is a process of evolution. In order to understand a machine so as to use it intelligently, or to make improvements upon it, it is necessary not only to know the machine as it actually is, but also to know the history of its development up to its present form.

The story of the evolution of a machine is, at best, but a crude illustration of the evolution of man. Nevertheless, the conclusion is the same. If we are to understand man, we must study not only his present physical and menial state, but also the history of his development. Yet those whose work is concerned directly with man - whether they be teachers, guiding the growth of the child; statesmen, formulating the laws and regulations by which men are to be controlled in their public actions; or physicians, who are supposed to instruct and to guide men in the care of their physical well-being - are often densely ignorant of the most rudimentary knowledge of the evolution of man as it is now known and understood by the leading scientists of the world.

To Know Man Is To Know Evolution

Our entire system of education, our ideas of health and disease, our social customs, the principles of our form of government; our ideas of right and wrong, of rewards and punishments, are all fundamentally concerned with the evolution of man, and when this knowledge is studied with as much application as are the ancient languages, we may expect to see humanity progress at a rate hitherto unknown.

The evolution of man has been very much misunderstood. The term "evolution" is a broad one. It may refer to the growth of the individual, or to the race. It may mean the development of strictly physical organs, or of mental habits, of social customs, or of material products of man's genius, as the great works of civilization in the form of recorded learning, and the wonderful products of man's building ingenuity as seen in modern cities.

Significance Of The Term "Evolution"

The subject of the evolution of the human race may be grouped into three general kinds of development or growth:

1 The development of the physical man.

2 The development of the mind.

3 The development of custom and of external civilization.

Evolution in these three directions has taken place simultaneously. The mind and the body depend upon each other for their life and actions; while customs are merely the product of many minds working together and communicating their ideas to each other.

The human race is but the sum of the individuals composing it. We cannot consider the development of the individual without considering him in his relation to the race, neither can we understand the development of the race without understanding the growth of the individual.

One distinction too often overlooked by those who are not familiar with physiological science is the difference between actual physical inheritance and external customs. I wish to dwell at length upon this distinction, because a lack of understanding upon this point has been the source of many errors of judgment on the part of those who have been interested in the subject of physical training and food science.

Difference between inherited and acquired characteristics

At birth the individual inherits an organism with certain tendencies, both physical and mental, but this inheritance should not be confused with the physical habits which the child acquires by training from its parents and its associates. Thus, the child may inherit a brilliant mind, a weak stomach, or a sixth finger, but the child does not inherit a liking for broiled lobster, or a fondness for golf, or for driving an aeroplane. These are acquired and developed as habits, the same as the child would learn English or French, or would cultivate a fancy for parting his hair in the middle, or on the left side.

The Three Great Proofs Of The Evolution Of Animal Life

At the present time scientists are agreed upon the general theory of the evolution of man. The discussions pro and con regarding this, which exist today, are either discussions of minor points which have not yet been clearly worked out, or are the discussions of people who have grasped only a portion of the idea of evolution, and who are ignorant of its broader conception and of the facts which science has brought to the light of day.

The three great proofs of evolution are:

1 The actual history of the past recorded as fossils in the rocks and in the relics of pre-historic races.

2 The existence in the world today of a range of animals and plants which shows living examples of earlier types.

3 The repetition of the development of man as found in the growth of the individual

These three separate records of the development of living beings are considered by scientists as a most conclusive proof of the truth of evolution. Recorded as fossils in the rocks, we find the story of the development of all life upon the earth, from its simplest to its highest forms of plants and animals that live today, among which is man.

The first forms of animal life were, in all probability, minute one-celled organisms; these left no visible fossil remains. As soon as animals developed hard parts in their bodies, such as shells and bones, we find a record of their existence as fossils. The earliest recorded forms of life were various kinds of sea-creatures, of which the modern Crustacea (lobsters, etc.), snails, clams, and various shellfishes are types. Later were developed boneless fishes, on the order of skates. After these came true fishes; then amphibia (frogs, etc.); then reptiles, birds, and, last of all, mammals, including man. The facts are the same, whether we take the history of the successive forms as recorded as fossils in the rocks, or the living representatives that remain to tell the story in another form.

The Earliest Forms Of Animal Life

The third proof, which is the story of evolution recorded in the growth and development of the individual, is yet more interesting. As life developed from simpler forms, each individual animal or plant became more complex, or carried a little further the process of growth. But the method of reproduction of new individuals remained fundamentally the same. Each individual began, like its ancestors, as a single-cell being. By the process of nutrition these single cells in each case would grow, divide, and produce various tissues and organs, but always repeating the general story of the development of the race.

The Single Cell Is The Nucleus

The growth of the human embryo offers many proofs of evolution, which are wholly unexplainable upon any other theory of the origin of man, and would in themselves prove the truth of this view of man's creation were the proofs of geology entirely lacking. A single example will serve as an illustration. The human embryo at a certain period develops gill slits in the neck, the same as the embryo of a fish. This formation of unused or rudimentary organs which are afterwards outgrown, is very common throughout the animal world. In the upper jaw of a calf there are formed at a certain period incisor teeth, which never grow through the gums, but are reabsorbed and disappear as the calf develops.

Gills In The Human Embryo

I will not go further into the proofs and facts of the general theory of the evolution of animal life, but will now consider the later period of the development of man, which will show us his relation to other animals, and from which we can derive much valuable information regarding his natural physiological requirements.

Man's Animal Kinship

The conception of man being descended from a monkey has been the subject of much wit and mirth.

The scientist is not concerned with this theory; he only claims that man is very closely related to certain monkey-like forms known as anthropoid apes. The proofs of this assertion are abundant and conclusive. In fact, anthropoid apes, such as gorillas, chimpanzees and orang-outangs, are much more closely related to man than they are to other kinds of monkeys. This relation is shown by very close resemblance between the anatomy of man and apes, especially as to the teeth and digestive organs. Other facts are now known, of which Darwin and early investigators were ignorant, which prove this relation in a much more striking manner.

Man's Relation To Anthropoid Apes

Late studies upon the growth of the embryo of anthropoid apes have shown that they were at certain periods almost indistinguishable from human embryos. Another proof, quite striking and interesting, is in the similarity of the parasites and diseases of men and apes. Scientists have, within the past few years, made a series of comparative investigations upon the blood and serum of men and apes, which have resulted in most remarkable discoveries. There are certain accurate tests known to the physiological chemist by which human blood may be distinguished from the blood of all other animals, but the blood of these man-like apes is an exception to this, and cannot be distinguished from human blood.