Lethal selection, on the contrary, constantly a.s.serts its power to reduce the reproductive rate, because the reproductive demands on the parents reduce their chances of life by interference with their natural ability of self-protection. This is quite true, but the a.n.a.lysis is incomplete, for an increased number of progeny not only decreases the life chances of the parents, but also of the young, by reducing the amount of care they receive.
In short, lethal selection and reproductive selection accomplish the same end--a change in the const.i.tution of the species--by different means; but they are so closely linked together and balanced that any change in the operation of one is likely to cause a change in the operation of the other. This will be clearer when the effect of reproductive selection is studied in man.
Recalling the truism that most human characters have a hereditary basis, it is evident that the const.i.tution of society will remain stable from generation to generation, only if each section of society is reproducing at the same rate as every other (and a.s.suming, for the moment, that the death-rate remains constant). Then if the birth-rate of one part of the population is altered, if it is decreased, for example, the next generation will contain proportionately fewer representatives of this cla.s.s, the succeeding generation fewer still, and so on indefinitely--unless a selective death-rate is operating at the same time. It is well known not only that the death-rate varies widely in different parts of the population, as was pointed out in the earlier part of this chapter, but that the birth-rate is rarely the same in any two sections of the population. Evidently, therefore, the make-up of society must necessarily be changing from generation to generation. It will be the object of the rest of this chapter to investigate the ways in which it is changing, while in the latter half of the book we shall point out some of the ways in which it might be changed to better advantage than it is at present.
s.e.xual selection, or differential success in marrying, will be discussed at some length in Chapter XI; here it may be pointed out that the number who fail to marry is very much greater than one often realizes. It has already been noted that a large part of the population dies before it reaches the age of marriage. Of 1,000 babies born in the United States, only 750 will reach the average age of marriage; in some countries half of the thousand will have fallen by that time. These dead certainly will leave no descendants; but even of the survivors, part will fail to marry. The returns of the thirteenth U. S. census showed that of the males 45-64 years of age, 10% were single, while 11% of the females, 35-44 years old, were single. Few marriages will take place after those ages. Add the number who died unmarried previous to those ages, but after the age of 20, and it is safe to say that at least one-third of the persons born in the United States die (early or late) without having married.
The consideration of those who died before the age of marriage properly comes under the head of lethal selection, but if attention is confined to those who, though reaching the age of marriage, fail to marry, s.e.xual selection still has importance. For instance, it is generally known (and some statistical proof will be given in Chapter XI) that beauty is directly a.s.sociated with the chance of marriage. The pretty girls in general marry earlier as well in larger percentage; many of the ugly ones will never find mates. Herbert Spencer argued ingeniously that beauty is a.s.sociated with general mental and moral superiority, and the more exact studies of recent years have tended to confirm his generalization. A recent, but not conclusive, investigation[65] showed beauty to be correlated with intelligence to the extent of .34. If this is confirmed, it offers a good ill.u.s.tration of the action of s.e.xual selection in furthering the progressive evolution of the race. Miss Gilmore, studying a group of normal school graduates, found a direct correlation between intelligence (as judged by cla.s.s marks) and early marriage after graduation. Anyone who would take the trouble could easily investigate numerous cases of this sort, which would show the effect of s.e.xual selection in perpetuating desirable qualities.
But s.e.xual selection no longer has the importance that it once had, for nowadays the mere fact of marriage is not a measure of fecundity, to the extent that it once was. In the old days of unlimited fecundity, the early marriage of a beautiful, or intelligent, woman meant a probable perpetuation of her endowments; but at present, when artificial restraint of fertility is so widespread, the result does not follow as a matter of course: and it is evident that the race is little or not at all helped by the early marriage of an attractive woman, if she has too few or no children.
Fecundal selection, then, is becoming the important phase of reproductive selection, in the evolution of civilized races. The differential birth-rate is, as we have often insisted, the all-important factor of eugenics, and it merits careful consideration from all sides.
Such consideration is made difficult by the inadequate vital statistics of the United States (which ranks with Turkey and China in this respect); but there is no doubt that the birth-rate as a whole is low, as compared with that of other countries; although as a whole it is not dangerously low and there is, of course, no necessary evil in a low birth-rate, of itself, if the quality be satisfactory. The U. S. Census tabulation for 1915 gives the following comparison of the number of babies born alive each year, per 1,000 population, in various countries:
Russia in Europe (1909) 44.0 j.a.pan (1911) 34.1 Italy (1913) 31.7 Austria (1912) 31.3 Spain (1913) 30.4 Austria (1913) 28.3 German Empire (1912) 28.3 Holland (1913) 28.1 Denmark (1913) 25.6 Norway (1913) 25.3 United States (registration area only, 1915) 24.9 England and Wales (1913) 24.1 Sweden (1912) 23.8 Switzerland (1913) 23.1 Belgium (1912) 22.6 France (1912) 19.0
The United States birth-rate may, on its face, appear high enough; but its face does not show that this height is due largely to the fecundity of immigrant women. Statistics to prove this are given in Chapter XIII, but may be supplemented here by some figures from Pittsburgh.
Ward 7, in that city, contains the homes of many well-to-do, and contains more representatives of the old American stock than any other ward in the city, having 56.4% of residents who are native born of native parents while the majority of the residents in nearly all the other wards in the city are either themselves foreign-born, or the offspring of foreign-born parents.
Ward 7 has the lowest birth-rate and the lowest rate of net increase of any ward in the city.
With this may be contrasted the sixth ward, which runs along the south bank of the Allegheny river. It is one of the great factory districts of the city, but also contains a large number of homes. Nearly 3,000 of its 14,817 males of voting age are illiterate. Its death-rate is the highest in the city. Almost nine-tenths of its residents are either foreigners or the children of foreigners. Its birth-rate is three times that of the seventh ward.
Taking into account all the wards of the city, it is found that the birth-rate _rises_ as one considers the wards which are marked by a large foreign population, illiteracy, poverty and a high death-rate. On the other hand, the birth-rate _falls_ as one pa.s.ses to the wards that have most native-born residents, most education, most prosperity--and, to some extent, education and prosperity denote efficiency and eugenic value. For 27 wards there is a high negative correlation (-.673), between birth-rate and percentage of native-born of native parents in the population. The correlation between illiteracy and net increase[66]
is +.731.
The net increase of Pittsburgh"s population, therefore, is greatest where the percentage of foreign-born and of illiterates is greatest.
The significance of such figures in natural selection must be evident.
Pittsburgh, like probably all large cities in civilized countries, breeds from the bottom. The lower a cla.s.s is in the scale of intelligence, the greater is its reproductive contribution. Recalling that intelligence is inherited, that like begets like in this respect, one can hardly feel encouraged over the quality of the population of Pittsburgh, a few generations hence.
Of course these illiterate foreign laborers are, from a eugenic point of view, not wholly bad. The picture should not be painted any blacker than the original. Some of these ignorant stocks, in another generation and with decent surroundings, will furnish excellent citizens.
But taken as a whole, it can hardly be supposed that the fecund stocks of Pittsburgh, with their illiteracy, squalor and tuberculosis, their high death-rates, their economic straits, are as good eugenic material as the families that are dying out in the more substantial residence section which their fathers created in the eastern part of the city.
And it can hardly be supposed that the city, and the nation, of the future, would not benefit by a change in the distribution of births, whereby more would come from the seventh ward and its like, and fewer from the sixth and its like.
Evidently, there is no difficulty about seeing this form of natural selection at work, and at work in such a way as greatly to change the character of one section of the species. For comparison, some figures are presented from European sources. In the French war budget of 1911 it appears that from 1,000 women between the ages of 15 and 50, in different districts of Paris, the number of yearly births was as follows:
Very poor 108 Poor 99 Well-to-do 72 Very prosperous 65 Rich 53 Very rich 35
Disregarding the last cla.s.s altogether, it is yet evident that while the mother in a wealthy home bears two children, the mother in the slums bears four. It is evident then that in Paris at the present time reproductive selection is changing the mental and moral composition of the population at a rapid rate, which can not be very materially reduced even if it is found that the death-rate in the poorer districts is considerably greater than it is on the more fashionable boulevards.
J. Bertillon has brought together[67] in a similar way data from a number of cities, showing the following birth-rates:
_Berlin_ _Vienna_ _London_ Very poor quarters 157 200 147 Poor quarters 129 164 140 Comfortable quarters 114 155 107 Very comfortable 96 153 107 Rich 63 107 87 Very rich 47 81 63 --- --- --- Average 102 153 109
Obviously, in all these cases reproductive selection will soon bring about such a change in the character of the population, that a much larger part of it than at present will have the hereditary characteristics of the poorer cla.s.ses and a much smaller part of it than at present the hereditary characteristics of the well-to-do cla.s.ses.
David Heron and others have recently studied[68] the relation which the birth-rate in different boroughs of London bears to their social and economic conditions. Using the correlation method, they found "that in London the birth-rate per 1,000 married women, aged 15 to 54, is highest where the conditions show the greatest poverty--namely, in quarters where p.a.w.nbrokers abound, where unskilled labor is the princ.i.p.al source of income, where consumption is most common and most deadly, where pauperism is most rife, and, finally, where the greatest proportion of the children born die in infancy. The correlation coefficients show that the a.s.sociation of these evil conditions with the relative number of children born is a very close one; and if the question is put in another way, and the calculations are based on measures of prosperity instead of on measures of poverty, a high degree of correlation is found between prosperity and a low birth-rate.
"It must not be supposed that a high rate of infant mortality, which almost invariably accompanies a high birth-rate, either in London or elsewhere, goes far toward counteracting the effects of the differential birth-rate. Where infant mortality is highest the average number of children above the age of two for each married woman is highest also, and although the chances of death at all ages are greater among the inhabitants of the poorer quarters, their rate of natural increase remains considerably higher than that of the inhabitants of the richer.
"From the detailed study of the figures made by Newsholme and Stevenson, conclusions essentially the same as those of Heron can be drawn....
Their first step was to divide the London boroughs into six groups according to the average number of domestic servants for 100 families in each. This is probably as good a measure of prosperity as any other.
They then determined the total birth-rate of the population in each group, and arrived at the following figures:
_Group_
I. 10 domestic servants for 100 families 34.97 II. 10-20 38.32 III. 20-30 25.99 IV. 30-40 25.83 V. 40-60 25.11 VI. Over 60 18.24
"In order to find out how far the differences shown by these figures are due to differences in the percentage of women who marry in each group and the age at which they marry, they corrected the figures in such a way as to make them represent what the birth-rates would be in each group, if the proportion of wives of each age to the whole population comprising the group was the same as it is in the whole of England and Wales. The corrected birth-rates thus obtained were as follows:
_Group_
I 31.56 II 25.82 III 25.63 IV 25.50 V 25.56 VI 20.45
"It will readily be seen that the effect of the correction has been to reduce the difference between the two extreme groups by about one-third, showing that to this extent it is due to the way in which they differ as to the average age and number of the women who marry. Further, Groups II, III, IV and V have all been brought to about the same level, with a corrected birth-rate about halfway between the highest and the lowest.
This shows that there is no gradual decrease in fertility a.s.sociated with a gradually increasing grade of prosperity, but that three sharply divided cla.s.ses may be distinguished: a very poor cla.s.s with a high degree of fertility, to which about a quarter of the population of London belong, a rich cla.s.s with a low degree of fertility, and a cla.s.s intermediate in both respects."
"Eugenics is less directly concerned with this side of the question that with the relative rate of increase of the different cla.s.ses. This may be found for the six groups in the usual way by deducting the death-rate from the birth-rate. The following figures for the rate of natural increase are then obtained:
_Group_
I 16.56 II 13.89 III 11.43 IV 13.81 V 10.29 VI 5.79
"The figures show in a manner which hardly admits of any doubt that in London at any rate the inhabitants of the poorest quarters--over a million in number--are reproducing themselves at a much greater rate than the more well-to-do."
A research on similar lines by S. R. Steinmetz[69] in Holland shows that the average number of children in the lowest cla.s.s families is 5.44.
People in industry or small trade, skilled mechanics and professors of theology have five children to the family; in other cla.s.ses the number is as follows:
Artists 4.30 Well-to-do Commercial Cla.s.ses 4.27 High Officials 4.00 University Professors (excluding theological) 3.50 23 Scholars and Artists of the first rank 2.60
It is not hard to see that the next generation in Holland is likely to have proportionately fewer gifted individuals than has the present one.
Fortunately, it is very probable that the differential birth-rate is not of such ominous import in rural districts as it is in cities, although some of the tribes of degenerates which live in the country show birth-rates of four to six children per wife.[70] But in the more highly civilized nations now, something like a half of the population lives in urban districts, and the startling extent to which these urban populations breed from the bottom involves a disastrous change in the balance of population within a few generations, unless it is in some way checked.
Just how great the change may be, statistically, has been emphasized by Karl Pearson, who points out that "50% of the married population provide 75% of the next generation," owing to the number of deaths before maturity, the number of celibates and the number of childless marriages. "The same rule may be expressed in another way: 50% of the next generation is produced by 25% of the married population." At this rate in a few generations the less efficient and socially valuable, with their large families, will overwhelm the more efficient and socially valuable, and their small families.
Fecundal selection is at work to-day on a large scale, changing the character of the population, and from a eugenic point of view changing it for the worse. Fortunately, it is not impossible to arrest this change.
But, it may be objected, is not this change merely "the survival of the fittest?" In a sense, yes; and it is necessary that the more intelligent cla.s.ses should make themselves "fitter" to survive, by a change of att.i.tude toward reproduction. But the dying-out of the intellectually superior part of the population is a pathological condition, not a part of normal evolution; for barring artificial interference with the birth-rate, fertility has been found to go hand in hand with general superiority. This demonstration is due to F. A. Woods" study[71] of 608 members of the royal families of Europe, among whom, for reasons of state, large families are desired, and among whom there has probably been little restraint on the birth-rate. Averaging the ratings of his individuals from grade 1, the mentally and physically very inferior, to grade 10, the mentally and physically very superior, he found that the number of children produced and brought to maturity increased in a fairly direct ratio. His figures are as follows:
BOTH s.e.xES (AVERAGED)
Grades for virtues 1 2 3 4 5 6 7 8 9 10 Average number of adult children. 1.66 2.86 2.99 2.41 3.44 3.49 3.05 3.03 3.93 3.83