[R] 12th Census. U. S., 1900, iii. Vital Statistics, p. LXXIX.
[S] F. Prinzing Medizinische Statistik, Verlag von Gustav Fischer in Jena, 1906.
| Year | All Ages (Stand- ard- ized) |
Deaths per 1,000 Persons at Subjoined Ages | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0–5 | 5–10 | 10–15 | 15–20 | 20–25 | 25–30 | 35–45 | 45–55 | 55–65 | 65–75 | 75–85 | 85 and up- wards |
Deaths of Infants under 1 yr. of Age per 1,000 Births | ||
| 1841–45 | 20.6 | 63.7 | 8.7 | 5.0 | 7.2 | 8.8 | 9.7 | 12.1 | 16.1 | 28.7 | 62.0 | 137.1 | 295.3 | 148 |
| 1846–50 | 22.4 | 68.7 | 9.4 | 5.6 | 7.7 | 9.8 | 10.9 | 13.6 | 18.1 | 31.4 | 65.9 | 145.8 | 306.6 | 157 |
| 1851–55 | 21.7 | 68.9 | 8.6 | 5.2 | 7.4 | 9.0 | 10.1 | 12.7 | 17.2 | 29.6 | 62.9 | 143.2 | 299.5 | 156 |
| 1856–60 | 20.7 | 66.9 | 8.3 | 4.7 | 6.7 | 8.3 | 9.4 | 12.0 | 16.1 | 28.4 | 60.9 | 136.6 | 293.4 | 152 |
| 1861–65 | 21.4 | 69.1 | 8.4 | 4.7 | 6.6 | 8.4 | 9.8 | 12.6 | 17.1 | 30.2 | 62.4 | 139.1 | 298.8 | 151 |
| 1866–70 | 21.2 | 68.1 | 7.6 | 4.3 | 6.2 | 8.0 | 9.9 | 12.9 | 17.6 | 30.6 | 63.2 | 141.7 | 294.3 | 157 |
| 1871–75 | 20.9 | 64.9 | 6.9 | 4.0 | 5.8 | 7.7 | 9.6 | 13.1 | 18.0 | 31.6 | 65.3 | 141.6 | 305.2 | 153 |
| 1876–80 | 19.8 | 61.9 | 6.1 | 3.5 | 4.9 | 6.5 | 8.4 | 12.3 | 17.5 | 31.6 | 64.7 | 142.9 | 311.5 | 145 |
| 1881–85 | 18.7 | 56.6 | 5.7 | 3.2 | 4.6 | 6.0 | 8.0 | 11.8 | 17.2 | 31.0 | 63.5 | 136.1 | 277.7 | 139 |
| 1886–90 | 18.5 | 56.9 | 4.9 | 2.8 | 4.1 | 5.3 | 7.2 | 11.1 | 17.1 | 31.8 | 66.3 | 139.0 | 290.3 | 143 |
| 1891–95 | 18.5 | 57.8 | 4.6 | 2.6 | 4.0 | 5.0 | 6.8 | 11.0 | 17.3 | 32.5 | 67.3 | 140.8 | 274.1 | 151 |
| 1896–1900 | 17.6 | 57.6 | 4.1 | 2.4 | 3.5 | 4.5 | 6.0 | 10.1 | 16.2 | 30.5 | 64.1 | 133.6 | 267.5 | 156 |
| 1901–05 | 16.0 | 50.2 | 3.7 | 2.2 | 3.1 | 4.0 | 5.4 | 8.9 | 14.9 | 28.7 | 59.4 | 127.3 | 258.6 | 138 |
| 1906–10 | 14.4 | 41.7 | 3.4 | 2.0 | 2.9 | 3.6 | 4.8 | 7.8 | 13.7 | 27.5 | 58.1 | 127.0 | 262.4 | 117 |
Note improvement since 1890 in death rate at every age period of life.
[T] Seventy-fifth Annual Report of the Registrar General of the Births, Deaths, and Marriages in England and Wales, 1912, p. 28.
DEATH RATES CLASSIFIED BY SEX, AGE, AND GENERAL NATIVITY, NEW YORK STATE: 1900 AND 1910[U]
[U] Willcox, Walter F., Special Report on Vital Statistics, 33d annual report, State Department of Health, State of New York, 1912.
| Age Period. | Native White. | Foreign Born White. | Coloured. | |||
|---|---|---|---|---|---|---|
| 1900 Death Rate. | 1910 Death Rate. | 1900 Death Rate. | 1910 Death Rate. | 1900 Death Rate. | 1910 Death Rate. | |
| All ages | 18.6 | 17.3 | 20.6 | 17.0 | 27.9 | 26.5 |
| Under 1 | 180.3 | 154.9 | 166.6 | 104.6 | 410.5 | 313.2 |
| 1–4 | 23.0 | 17.5 | 31.6 | 21.7 | 57.0 | 46.6 |
| 5–9 | 5.0 | 4.0 | 5.3 | 3.4 | 11.0 | 7.4 |
| 10–14 | 3.0 | 2.3 | 2.5 | 2.5 | 8.1 | 7.1 |
| 15–19 | 4.6 | 3.9 | 4.9 | 4.3 | 10.2 | 11.3 |
| 20–24 | 7.4 | 5.9 | 6.8 | 5.2 | 13.8 | 11.2 |
| 25–29 | 9.4 | 7.5 | 7.9 | 5.6 | 14.0 | 11.8 |
| 30–34 | 11.3 | 9.6 | 9.3 | 6.9 | 15.5 | 19.6 |
| 35–39 | 12.4 | 12.3 | 12.2 | 9.8 | 15.1 | 19.8 |
| 40–44 | 13.6 | 13.7 | 15.0 | 13.2 | 19.3 | 23.9 |
| 45–49 | 14.7 | 16.6 | 19.8 | 17.7 | 30.9 | 28.7 |
| 50–54 | 17.2 | 19.6 | 26.0 | 23.6 | 32.0 | 32.4 |
| 55–59 | 22.3 | 27.0 | 34.3 | 35.4 | 43.8 | 45.3 |
| 60–64 | 31.0 | 37.4 | 43.4 | 46.9 | 40.5 | 57.4 |
| 65–69 | 46.3 | 53.5 | 61.9 | 65.6 | 72.4 | 76.5 |
| 70–74 | 67.5 | 72.3 | 82.2 | 85.2 | 90.2 | 77.5 |
| 75–79 | 109.4 | 118.1 | 119.4 | 115.7 | 125.0 | 130.6 |
| 80–84 | 156.1 | 163.9 | 182.4 | 190.7 | 163.1 | 163.5 |
| 85–89 | 243.8 | 246.0 | 239.0 | 243.3 | 122.8 | 183.7 |
| 90 &over | 366.7 | 394.9 | 351.0 | 367.6 | 280.0 | 263.2 |
The tables on this and the opposite page show the same general trend of mortality in New York State that is exhibited in the Registration States generally and wherever reliable statistics are obtainable. It will be noted, however, that there is little change in the mortality rate among women until age sixty, when a decidedly increased mortality rate is shown comparing 1910 with 1900. It will also be noted that this unfavorable trend in mortality in later life is manifested among native whites, foreign born and colored citizens alike.
| Ages | New York City[V] 1909–1911. |
England and Wales[W] 1910–1912. |
London[W] 1911–1912. |
|||
|---|---|---|---|---|---|---|
| Males | Females | Males | Females | Males | Females | |
| At birth | 44.55 | 48.8 | 51.50 | 55.35 | ... | ... |
| 10 | 46.95 | 50.4 | 53.08 | 55.91 | ... | ... |
| 20 | 38.26 | 41.7 | 44.21 | 47.10 | 42.35 | 46.71 |
| 30 | 30.34 | 33.6 | 35.81 | 38.54 | 33.87 | 37.94 |
| 40 | 23.34 | 26.2 | 27.74 | 30.30 | 26.03 | 29.67 |
| 50 | 17.11 | 19.1 | 20.29 | 22.51 | 19.09 | 22.17 |
| 60 | 11.71 | 12.9 | 13.78 | 15.48 | 13.09 | 15.39 |
| 70 | 7.66 | 8.2 | 8.53 | 9.58 | 8.17 | 9.57 |
| 80 | 4.66 | 4.9 | 4.90 | 5.49 | 4.79 | 5.39 |
| 90 | 2.24 | 2.8 | 2.87 | 3.16 | 2.75 | 3.10 |
The above tables show, both among males and females, that the expectation of life is greater at every ago period in England and Wales and in London than in New York.
[V] Annual Report, Department of Health, City of New York, 1912, pp. 176–177.
[W] Supplement to the Seventy-Fifth Annual Report of the Registrar-General of Births, Deaths and Marriages in England and Wales. Part I—Life Tables, pp. 56–85.
| Ages | 1875–1880.[X] | 1881–1890.[X] | 1891–1900.[X] | 1901–1910.[Y] | ||||
|---|---|---|---|---|---|---|---|---|
| Males | Females | Males | Females | Males | Females | Males | Females | |
| 1–2 | 71.8 | 69.1 | 70.2 | 68.0 | 58.0 | 55.5 | 45.3 | 43.1 |
| 2–3 | 37.1 | 36.1 | 36.3 | 34.6 | 24.7 | 23.8 | 16.5 | 16.0 |
| 3–5 | 22.2 | 21.7 | 20.8 | 20.7 | 14.2 | 13.9 | 8.9 | 8.8 |
| 5–10 | 9.3 | 9.2 | 8.8 | 9.0 | 5.9 | 6.1 | 4.2 | 4.4 |
| 10–15 | 3.9 | 4.3 | 3.8 | 4.3 | 2.9 | 3.3 | 2.4 | 2.7 |
| 15–20 | 5.1 | 4.6 | 4.8 | 4.5 | 4.3 | 3.8 | 4.0 | 3.6 |
| 20–25 | 7.7 | 6.3 | 7.0 | 5.8 | 6.0 | 5.1 | 5.2 | 4.6 |
| 25–30 | 8.6 | 8.2 | 7.6 | 7.5 | 6.1 | 6.1 | 5.3 | 5.5 |
| 30–40 | 10.9 | 10.3 | 10.6 | 9.7 | 8.3 | 7.9 | 7.0 | 6.7 |
| 40–50 | 16.7 | 12.3 | 16.3 | 11.7 | 14.3 | 10.0 | 12.5 | 8.6 |
| 50–60 | 27.6 | 20.7 | 26.9 | 19.8 | 24.2 | 17.5 | 23.5 | 16.0 |
| 60–70 | 53.0 | 46.3 | 51.4 | 44.8 | 48.7 | 42.0 | 45.5 | 37.4 |
| 70–80 | 113.3 | 106.2 | 110.2 | 113.9 | 102.5 | 97.1 | 100.6 | 102.0 |
| 80 & over | 236.4 | 227.2 | 238.2 | 229.0 | 233.1 | 223.3 | 214.4 | 202.6 |
Note that in both sexes there was a steady and substantial decline in the death rate at all age periods of life after 1875.
[X] Königlich Statistisches Bureau in Berlin Preussische Statistik. Hft. 184, p. iv. ff., Berlin.
[Y] Zeitschrift des Königlich Preussichen Statistichen Landesamts, Berlin, 1912, p. xvii.
| Ages | 1880–1889 | 1890–1900 | ||
|---|---|---|---|---|
| Males | Females | Males | Females | |
| 0–5 | 53.1 | 46.0 | 48.5 | 40.8 |
| 5–10 | 7.2 | 7.7 | 5.6 | 6.0 |
| 10–15 | 4.4 | 5.6 | 3.6 | 4.6 |
| 15–20 | 4.9 | 5.8 | 4.5 | 4.7 |
| 20–25 | 7.0 | 6.1 | 6.0 | 4.9 |
| 25–30 | 6.5 | 7.4 | 5.5 | 5.6 |
| 30–35 | 6.8 | 7.9 | 6.1 | 6.5 |
| 35–40 | 7.8 | 8.4 | 7.7 | 7.5 |
| 40–45 | 9.8 | 9.3 | 9.3 | 8.2 |
| 45–50 | 12.6 | 10.2 | 11.6 | 9.1 |
| 50–55 | 16.8 | 12.2 | 15.7 | 11.8 |
| 55–60 | 22.6 | 17.0 | 22.0 | 16.4 |
| 60–65 | 33.3 | 26.1 | 30.7 | 24.2 |
| 65–70 | 46.9 | 39.2 | 44.7 | 36.7 |
| 70–75 | 70.0 | 58.3 | 74.5 | 65.0 |
| 75–80 | 104.9 | 92.9 | 115.0 | 98.9 |
| 80–85 | 178.7 | 157.4 | 169.4 | 151.6 |
| 85–90 | 246.7 | 210.9 | 250.1 | 226.5 |
| 90-over | 392.3 | 350.1 | 425.6 | 373.2 |
Note the improvement in mortality at nearly every age period of life, in both sexes.
Befolkningsforholdene i. Denmark i. 19. Arrhundrede, p. 125. Denmark Statistiske Tabelvaerk, Ser. 5, Litra A. no. 5.
| Ages | 0–5 | 5–10 | 10–15 | 15–25 | 25–35 | 35–45 | 45–55 | 55–65 | 65 over |
|---|---|---|---|---|---|---|---|---|---|
| Years | |||||||||
| 1801–10 | 79.0 | 12.1 | 7.2 | 8.5 | 11.0 | 14.9 | 22.7 | 40.8 | 111.4 |
| 1811–20 | 76.0 | 9.7 | 5.6 | 7.2 | 9.9 | 14.3 | 21.0 | 37.6 | 102.9 |
| 1821–30 | 63.1 | 7.6 | 4.5 | 6.1 | 9.4 | 13.6 | 20.1 | 35.4 | 96.9 |
| 1831–40 | 60.3 | 7.5 | 4.7 | 6.0 | 9.8 | 14.3 | 20.8 | 35.6 | 102.1 |
| 1841–50 | 56.8 | 7.8 | 4.4 | 5.5 | 8.0 | 12.2 | 18.1 | 31.8 | 97.1 |
| 1851–60 | 60.5 | 10.9 | 5.5 | 6.1 | 8.4 | 11.9 | 17.9 | 32.1 | 91.6 |
| 1861–70 | 57.3 | 9.1 | 4.4 | 5.4 | 7.2 | 10.1 | 15.1 | 28.7 | 87.2 |
| 1871–80 | 52.3 | 8.5 | 4.2 | 5.3 | 7.4 | 9.3 | 13.1 | 23.6 | 79.4 |
| 1881–90 | 43.6 | 7.7 | 4.0 | 5.2 | 6.6 | 8.2 | 11.5 | 21.1 | 71.4 |
| 1891–00 | 36.9 | 6.0 | 3.6 | 5.4 | 6.5 | 7.8 | 10.9 | 19.7 | 71.3 |
Note the pronounced fall in the death rate at every age period during the past century.
[Z] F. Prinzing Medizinische Statistik, Verlag von Gustav Fischer in Jena, 1906.
The remedies, however, are plainly indicated:
- Eugenics, to improve the stock.
- Periodic physical examinations to detect the earliest signs of disease, and especially infective foci in the head, such as diseased gums, tooth sockets, tonsils, nasal cavities, etc.
- The practice of personal hygiene along the lines of ascertained individual needs.
Cancer, another disease heavily on the increase in all civilized countries, may be combated by similar measures.
SECTION IX
EUGENICS
“How to Live” deals mainly with personal hygiene, that is, the proper care of the individual. Hygienic improvement is limited, however, to the attainment of the best of which an individual is capable. Eugenics deals with the even more vital subject of improving the inherent type and capacities of the individuals of the future. It has been but briefly touched upon in this volume.
Eugenic improvement is attainable through the control of heredity. By heredity is meant the action of elements which control the development of the individual, and determine his constitution or makeup. The laws of Nature governing this action are now known in part, so that advantage can be taken of them to bring about the hereditary improvement of the race, generation by generation.
Eugenics is not simply sex hygiene, as many have come to consider it, owing to the liberal use of the word Eugenics by the sex hygienists. Sex hygiene is, of course, one of the considerations in eugenic improvement.
Eugenics is not, furthermore, the science of improving the physical organism only, as has been erroneously assumed by certain uninformed publicists, a point of view which has been promoted by cartoonists, who find it good sport for their pens.
Eugenics does not require the old Spartan practise of infanticide, nor does Eugenics propose to do violence in any other way to humanitarian or religious feeling.
Eugenics does not mean, as some have imagined, compulsory or government-made marriages.
Nor is Eugenics the science of improving the human stock by matings that are academically ideal, but which lack the element of individual attraction and instinctive love.
There was a time when the inherent personality of a man, the color of his eyes, the capacity of his mind, the quality of his character, seemed clearly subject to the caprice of forces beyond the reach of mortal perception. In attempting to trace the source of a personality, hereditarily, no constancy could be detected in its relation to the lives from which it arose. A child was never absolutely like brother, sister, mother, father or grandparent.
An epoch-making discovery in 1865 by an Austrian monk named Mendel,[57] and later discoveries by a number of other scientists, revealed the subdivisibility of each individual into many distinct units or traits, the hereditary sources of which were clearly traceable, leading to various individuals of the family line, and not to one individual alone. Furthermore, it was found that the lack of a certain trait sometimes appears as a trait in itself, just as darkness seems like a condition in itself rather than as an absence of light.
These discoveries changed the whole current of thought regarding heredity, and the constancy of its action, as well as its controllability. It also emphasized the fact that it does make a difference whom one marries as to the character of the resulting offspring. Their makeup is not subject to the caprice of forces beyond human perception, but is in some degree subject to control.
Out of these discoveries has arisen the science of Eugenics. Sir Francis Galton, of England, was the first to start a world movement for its application toward conscious betterment of the human stock.
From the known laws governing the inheritability of unit-traits, it is apparently necessary, in the betterment of the race, to follow a few important rules:
- Learn to analyze individuals into their inheritable traits—physical, mental and moral.
- Differentiate between socially noble and ignoble traits, between social and educational veneer and sterling inherent capacity.
- Do not expect physical, mental and moral perfection in any one individual, but look for a majority of sterling traits.
- Observe the presence or absence of specific traits in individuals at all ages of successive generations and fraternities of a family line.
- Learn how to estimate the inheritability of such traits in a family line, upon specific mating with another family line.
- Join your family line to one which is strong in respect to the traits in which yours is weak.
- But remember also that injuries can be inflicted on offspring by unhygienic living.
Some of the characteristics in Man’s complex known to act hereditarily and to be traceable to distinct sources on family lines are as follows:[58]
Physical Traits.—Character of the facial features, color of the eyes, hair and skin, stature, weight, energy, strength, endurance, quickness, commanding presence, vivacity of manner, general bodily soundness; also defects of many kinds, such as those of the nervous system, of the speech, eyes, ears, skin, also baldness, defects of the muscular system, blood, thyroid glands, vascular system, respiratory system, digestive system, reproductive organs; also defects and peculiarities of the skeleton, etc. This does not mean that all shortcomings are inherited. It does mean, however, that the type of organism is inheritable which lacks resistance to the germs and other precipitating factors in bringing about the disease.
Mental Traits.—Among the mental characteristics known to arise from traceable hereditary sources may be mentioned factors in musical ability, artistic composition, literary ability, mechanical skill, calculating ability, inventive ability, memory, ability to spell, fluency in conversation, aptness in languages, military talent, acquisitiveness, attention, story-telling, poetic ability; and, on the other hand, insanity, feeble-mindedness of many types, epilepsy. These are suggestive of the inheritability of many other mental traits not yet studied.
Moral Traits.—Among the moral traits known to possess inheritable elements are generosity, piousness, independence, industry, will-power, faithfulness, fairness, sociability, reliability, self-reliance, tendency to work hard, perseverance, carefulness, impulsiveness, temperance, high-spiritedness, joviality, benignity, quietness, cheerfulness, hospitality, sympathy, humorousness, love of fun, neighborliness, love of frontier life, love of travel and of adventure. The same may be said of immoral traits, such as criminality, pauperism, delinquency, irascibility, lying, truancy, superstition, clannishness, secretiveness, despondency, slyness, exclusiveness, vanity, cunning, cruelty, quickness to anger, revengefulness, etc.
These physical, mental and moral peculiarities are not scattered evenly through the population, but exist on certain family lines only.
For instance, one-tenth of the deaths that occur in the United States are from tuberculosis. But this does not mean that one-tenth of all families die of the disease. On the contrary, some families lose more than half their numbers from it, while other families lose almost none at all. The 10 per cent. is simply the average of all. The percentage is high among the Irish, and low among the Jews. Life insurance companies take consideration of this fact in examining applicants for insurance. A family history of tuberculosis counts against even a healthy applicant, not because of a belief that tuberculosis is directly inheritable, but because non-resistant types, especially light-weights, are known to be transmitted. A profound influence toward checking this malady would evidently be exerted if the matings on the family lines exhibiting the characteristic of susceptibility were to cease, and thus the perpetuation of susceptible types checked.
The same is true of crime. The 80,000 prisoners constantly supported in the United States are recruited not evenly from the general population, but mainly from certain family breeds.[59] Criminality among “The Jukes” is a rule, among Jonathan Edwards’ descendants, the exception. The same is true of mental abilities of different kinds. Galton showed that the prominent English judges, statesmen, chancellors, etc., were furnished by certain family lines only, and were not drawn evenly from all families.[60] The same is true of feeble-mindedness.[61]
The question of what traits are desirable and what traits are undesirable might seem, on first thought, rather a difficult matter to determine. Few of us would like to have our neighbor’s taste in the matter constituted as a standard of judgment upon our own traits. There is one standard of judgment, however, that is so broad and impersonal and so founded on the elements in society to which all individuals are subject, that it can justly serve as a line of division between the desirability and undesirability, broadly speaking, of individual traits for perpetuation. This is the measurement by the standard of social worth and service commonly designated as “fitness.”[62] Above this dividing line may be roughly grouped the genius, the specially skilled, the mediocre, who are a service to society, or at least not a burden. Below this line may be grouped those feeble-minded, paupers, criminals, insane, weak and sick, who are a burden, economically and socially. That is, a person’s traits are desirable of perpetuation if so balanced as to render the individual not a burden to others.
It must undoubtedly be true that many families possess, inherently, traits of ability which have never had an opportunity to exhibit themselves. This may account for the apparently sudden appearance of great men and women without obvious hereditary background. It is plainly possible, furthermore, to bring about a special combination of two family lines, the mental traits on neither of which exhibit remarkableness, but which, when combined, bring an extremely happy result.
Mental ability does not depend upon education. Education can only enable an individual to utilize more fully his inherent ability; it cannot increase capacity.
The same is true, of course, of physical capacity. Sandow has an extraordinary muscular ability, developed by certain exercises. Similar exercises will not, however, develop all men into Sandows, no matter how constant their faith and persistent their efforts. Sandow was, we may assume, hereditarily gifted with a superior muscular capacity, which his exercises have enabled him to fully develop. It is true, however, that few people ever realize their full physical and mental capacities, owing to lack of opportunity, inclination, etc., and that there generally exist untold possibilities for improvement for those who wish to get the most out of themselves.
It is apparent that the make-up of an individual is the result of a very complex combination of traits. For this reason, the makeup is not likely to fall heir to all “bad” traits, any more than it is to all “good” traits. Even the feeble-minded, who have fallen heir to such an intensely undesirable trait—or rather, to the lack of intensely desirable traits—in many instances have simultaneously inherited many desirable traits, such as kindness, gentleness and generosity, often lacking in those possessed of scholarly capacities. Many women of the border-line type of feeble-mindedness, where mental incapacity often passes for innocence, possess the qualities of charm felt in children, and are consequently quickly selected in marriage. If a mentally able man possess as an ideal of womanhood other traits than mental capacity, no amount of schooling for his child can make up for the difference between the mental capacity of the offspring of such a mating, and the offspring of a mating with an able-minded woman. Although the trait of able-mindedness is dominant, so that the mating of an able and a feeble mind will result in fairly able-minded offspring, who may even be above the average, mentally, such offspring carry in their own germ plasm the defect derived from their feeble-minded parent, which defect may then be passed on to future generations through the germ plasm from which their children get their inheritance. A mother’s hereditary influence on the child is just as important a factor as the father’s, generally speaking. Where feeble-mindedness exists on a family line, care should be exercised by the able-minded members of that line not to mate with another line possessing cases of feeble-mindedness, lest the offspring then fall heir to feeble-mindedness, which can skip a generation. An appreciation of what is feeble-minded, and a realization of its inheritability can not help but modify a man or a woman’s admiration for the traits or lack of traits which it embraces.
Persons possessing weak physical makeups may possess strong mental capacities, and vice-versa. Persons of superior mental capacities may lack loftiness of character. It might happen that in so mating as to prevent the perpetuation of an undesirable trait, physical, mental or moral, a desirable trait would be lost along with it. In any mating transaction, therefore, choice must necessarily compromise upon the favorable hereditary action of a majority of the traits on the two family lines. One must relinquish any quest for perfection. After eliminating the individuals possessing the grossly unsocial traits below the dividing line of social fitness, one must choose with respect to a majority of socially fit traits, in addition to the elements of personal congeniality and affinity. The two last-named elements, however, generally serve as useful narcotics in blinding the mating individuals to the existence of the compromise, and the real becomes the ideal.
Each trait in the mosaic of one person is transmitted or not transmitted to a child according to the mating of that particular trait—mating with trait or lack of trait—rather than according to the mating of the two persons as a whole. That is, when a man and woman marry and bear offspring, it is not the mating of two units, but it is the mating of myriads of pairs of units—the units being the constituent traits and lack of traits (contained in some mysterious way in the germ plasm), each trait-mating producing its own trait-offspring. The collection of these trait-offspring makes up the child.
It has been observed that traits differ with respect to their action in mating. Given a specific type of trait-mating, say of a trait with like trait, or trait with the lack of that trait, some types always reappear in the next generation or else are lost entirely from the family line unless reinfused, whereas other types of traits may not reappear in the next generation, but still appear in a generation further removed. Another type of trait is transmissible only by one sex of a family line, and can not be transmitted by the other sex.
From these facts, it is readily understandable how important becomes the consideration of the marriage of relatives, such as cousins,[63] who are, of course, individuals of the same family line, whose mating brings together like groups of traits, thus strengthening the existence of these traits, whether desirable or undesirable. Cousin marriages, when the family possess traits of mental ability, may result in children who are geniuses; but cousin marriages, when the family line possesses traits of mental inability, may result disastrously with respect to offspring. Family lines possessing traits of mental weakness should most assuredly join only to family lines possessing traits of strength in those regards.
In calculating the inheritability of traits, it is also necessary to consider that certain physical, mental and moral traits flower at the arrival of certain ages only. It is necessary to look along the whole line of a life, as traits may exist at one age and not at another. A boy’s beard does not appear until puberty. Likewise, other physical and mental and moral traits sometimes do not manifest themselves until specific ages, according to the type of the family breed. Because a parent dies before the development of the trait does not preclude its transmissibility to his offspring. Huntington’s chorea, an extremely undesirable trait, does not develop until middle life, but is transmissible to offspring even though the father dies from some other cause before the period when the disease in his own person would be expected to appear.
We can best understand the laws governing the inheritance of traits by taking a few concrete cases. The first case is that of an Andalusian fowl. We shall consider the two species, pure bred black and pure bred white, and confine ourselves to observing the inheritance of the single characteristic, plumage color. Of course, as long as the black mate only with the black their children will be black, and as long as the white mate with white the children will be white. But if a white mates with a black, the children will not be either black or white, but blue. All will be blue. But the most interesting facts appear in the next generation, when these hybrid blue fowls mate with black or white, or with each other. The original of the cross between the white and the black is an entirely new color blue, which may be considered a sort of amalgam of black and white. But a cross between the blue and the black will not be any new color, but will be either black or blue—and the chances are even. That is, in the long run about half of the children of the blue and black parents will be blue and half will be black. None of the children will be white. So also crossing the blue with the white will result in half of the children being blue and half, white. Still more curious is the result of mating blue with blue. One might imagine that in this case all the children would be blue, but only half will be blue, while a quarter will be black and a quarter white.
These laws are a curious mixture of chance and certainty. In certain circumstances, as we have seen, we can predict with certainty that the offspring will be black, white, blue, or whatever the case may be. In other circumstances we can only state what the chances are. But these chances can be definitely stated as one in two, one in four or whatever it may be, and where there are large numbers of offspring this amounts to a practical certainty that definite proportions will have this or that color, or other characteristics.
Two parents are like two baskets or bundles of traits from which the child takes its traits at random. In the wonderful play of Maeterlinck’s, called the “Bluebird,” we are taken to the “land before birth,” where the children are waiting to be born, having selected their parents to be. Of course, this is only a pleasant fancy, like the advice of Oliver Wendell Holmes to children to choose good grandparents, but it is a useful fancy which will help us to understand the laws of heredity. The child of the Andalusian fowl takes its color from its two parents on the same principle as a lottery in which it would take two beans, white or black as the case might be, from each of two baskets. Every individual is a sort of basket containing two beans, as it were. It took one of these two beans from each parent and will give one to each child.
With this picture of a bean lottery before us it is very easy to understand how the colors of Andalusian fowls are inherited. When two black fowls mate, the offspring must be black, because in this case each parent basket contains a pair of black beans, so to speak, so that the child taking one black bean from each basket will necessarily have a black pair. For the same reason the child of two white fowls must be white, but when a black and white fowl mate, the child takes a white bean from one parent and a black from the other, its own color being resultant or amalgam of the two, which in the case of the Andalusian fowl is blue. Since every such hybrid child has this same combination of a white and a black bean, all these hybrids are alike. All are blue. It is important to remember that this hybrid blue is only a sort of mechanical mixture of black and white, and that the black and white are still separate beans, as it were.
But now suppose a hybrid or blue fowl to mate with a white. This means that the child takes from the white parent or basket one of the two white beans and from the blue parent or basket, one of the two beans, of which one is white and the other, black; the bean taken from the first or white basket must be white, but that taken from the second or blue or hybrid basket may be either white or black. It is a lottery with an even chance of drawing white or black. In the long run, half of the children will draw white and half, black. Those which draw the white will, since they also drew white from the other parent, be wholly white, but those which drew the black will be blue, since they will have one black and one white bean. We see, too, that the white child is just as truly white as though it had not had a hybrid parent; for of the two elements or beans which the hybrid carried, the black one was left behind untaken. We see that the blue child is a hybrid exactly like its hybrid parent, and not any new kind of cross between the blue and the white. In short, the children of a blue and white are either the one or the other and not a mixture. In the same way if a blue mates with a black, half of the children will be black and half blue.
Finally we come to the mating of a blue with a blue. Here the lottery is to pick a bean from two baskets, each basket containing both white and black beans in equal numbers. When at random one is taken from either of these two baskets there is an even chance that the bean from the father is white or black and an even chance that the bean from the mother is white or black.
Now, what is the chance that the child draws a white bean from both baskets? Evidently it is one chance in four; for there are four ways equally probable in which you can take these beans, viz.: (1) black from the father basket and black from the mother, (2) white from the father and white from the mother, (3) white from the father and black from the mother, (4) black from the father and white from the mother. So the children could draw both white once in four times, both black once in four, and a white and a black in the other two cases. And that is why from two blue Andalusian fowls, on the average you will have one-quarter of the children black, one-quarter white, and the other two-quarters, blue. Again let us stop to emphasize the fact that the black children of these hybrids are just as pure blooded as their black grandparent, and will mate with other pure-blooded black in exactly the same way as though there had never been any white in their ancestry. The white strain has been left behind, or been “bred out.”
We have spoken of one character or characteristic—color. The same laws apply to other characters. Often different characters are inherited quite independently of one another. Each of us is a basket or bundle of very many qualities, each quality being a little compartment of the basket with two beans in it. There is, as it were, a pair of beans for every unit trait, whether that trait relates to color, to musical ability, or to any one of hundreds of other kinds.
To summarize the laws of inheritance of the unit character called color, in Andalusian fowl, we have really six ways in which we can consider mating of the three colored fowls (black, white, blue): (1) black may mate with black, in which case all the offspring will be black, (2) white may mate with white, in which case all the offspring will be white, (3) a black may mate with a white, in which case the offspring will all be blue—a hybrid containing both black and blue elements, (4) blue may mate with a black, in which case half the offspring will be pure bred black, and half hybrid blue, (5) a blue may mate with a white, in which case half the offspring will be white and half blue, (6) blue may mate with blue in which case a quarter of the offspring will be white, a quarter black and a half blue.