The Science of Human Nature. William Henry Pyle
feeble-minded parents will have only feeble-minded children. Feeble-mindedness acts in heredity as does the white corn in the example given above. If one parent only is feeble-minded, the other being normal, all of the children will be normal, just as all of the corn, in the first generation after the crossing, was yellow. But these children whose parents are the one normal and the other feeble-minded, while themselves normal, transmit feeble-mindedness in equal ratio with normality. It works out as follows: If a feeble-minded person marry a person of sound mind and sound stock, the children will all be of sound, normal mind. If these children take as husbands and wives men and women who had for parents one normal and one feeble-minded person, their children will be one fourth feeble-minded and three fourths of them normal.
To summarize the various conditions: If a feeble-minded person marry a feeble-minded person, all the children will be feeble-minded. If a feeble-minded person marry a sound, normal person (pure stock), all the children will be normal. If the children, in the last case, marry others like themselves as to origin, one fourth of their offspring will be feeble-minded. If such hybrid children marry feeble-minded persons, one half of the offspring will be feeble-minded. It is rash to prophesy, but future studies of heredity may show that Mendelism, or some modification of the principle, always holds true of mind as well as of body.
Little can be said about the transmission of particular definite mental traits, such as the various aspects of memory, association, attention, temperament, etc. Before we can speak with any certainty here, we must make very careful experimental studies of these mental traits in parents and offspring. No such work has been done. All we have at the present time is the result of general observation.
Improvement of the Race. Eugenics is the science of improvement of the human race by breeding. While we can train children and thereby make them much better than they would be without such training, this training does not improve the stock. The improvement of the stock can be accomplished only through breeding from the best and preventing the poor stock from leaving offspring. This is a well-known principle in the breeding of domestic animals.
It is doubtless just as true in the case of human beings. The hygienic and scientific rearing of children is good for the children and makes their lives better, but probably does not affect their offspring. We should not forget that all the social and educational influences die with the generation that receives them. They must be impressed by training on the next generation or that generation will receive no influence from them. The characters which we acquire in our lifetime seem not to be transmitted to our children, except through what is known as social heredity, which is merely the taking on of characteristics through imitation. Our children must go through all the labor of learning to read, write, spell, add, multiply, subtract, and divide, which we went through. Moral traits, manners and customs, and other habits and ideals of social importance must be acquired by each successive generation.
Heredity versus Environment. The question is often asked whether heredity or the influence of environment has the most to do with the final outcome of one’s life. It is a rather useless question to ask, for what a human being or anything else in the world does depends upon what it is itself and what the things and forces are that act upon it. Heredity sets a limitation for us, fixes the possibilities. The circumstances of life determine what we will do with our inherited abilities and characteristics. Hereditary influences incline us to be tall or short, fat or lean, light or dark. The characteristics of our memory, association, imagination, our learning capacity, etc., are determined by heredity. Of course, how far these various aspects develop is to some extent dependent upon the favorable or unfavorable influences of the environment. What is possible for us to do is settled by heredity; what we may actually do, what we may have the opportunity to do, is largely a matter of the circumstances of life.
In certain parts of New England, the number of men who become famous in art, science, or literature is very great compared to the number in some other parts of our country. As far as we have any evidence, the native stocks are the same in the two cases, but in New England the influences turn men into the direction of science, art, and literature. Everything there is favorable. In other parts of the country, the influences turn men into other spheres of activity. They become large landowners, men of business and affairs.
The question may be asked whether genius makes its way to the front in spite of unfavorable circumstances. Sometimes it doubtless does. But pugnacity and perseverance are not necessarily connected with intellectual genius. Genius may be as likely to be timid as belligerent. Therefore unfavorable circumstances may crush many a genius.
The public schools ought to be on the watch for genius in any and all kinds of work. When a genius is found, proper training ought to be provided to develop this genius for the good of society as well as for the good of the individual himself. A few children show ability in drawing and painting, others in music, others in mechanical invention, some in literary construction. When it is found that this ability is undoubtedly a native gift and not a passing whim, special opportunity should be provided for its development and training. It will be better for the general welfare, as well as for individual happiness, if each does in life that for which he is by nature best fitted. For most of us, however, there is not much difference in our abilities. We can do one thing as well as we can many other things. But in a few there are undoubted special native gifts.
Summary. This is an orderly world, in which everything has a cause. All events are connected in a chain of causes and effects. Human beings live in this world of natural law and are subject to it. Human life is completely within this world of law and order and is a part of it. Education is possible only because we can change human beings by having influences act upon them.
Individuals receive their original traits from their ancestors, probably as parts or units. Mendelism is the doctrine of the pure transmission of unit characters. Eugenics is the science of improving the human race by selective breeding. An individual’s life is the result of the interaction of his hereditary characteristics and his environment.
CLASS EXERCISES
1 Try to find rock containing the remains of animals. You can get information on such matters from a textbook on geology.
2 Read in a geology about the different geological epochs in the history of the earth.
3 Make a comparison of the length of infancy in the lower animals and in man. What is the significance of what you find? What advantage does it give man?
4 What is natural selection? How does it lead to change in animals? Does natural selection still operate among human beings? (See a modern textbook on zoölogy.)
5 By observation and from consulting a zoölogy, learn about the different classes of animal forms, from low forms to high forms.
6 By studying domestic animals, see what you can learn about heredity. Enumerate all the points that you find bearing upon heredity.
7 In a similar way, make a study of heredity in your family. Consider such characteristics as height, weight, shape of head, shape of nose, hair and eye color. Can you find any evidence of the inheritance of mental traits?
8 Make a complete outline of Chapter II.
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