R. A. Fisher: The Social Selection of Fertility (1930)

Chapter 11 of The Genetical Theory Of Natural Selection:

XI

THE SOCIAL SELECTION OF FERTILITY

History of the theory. Infertility in all classes, irrespective of its cause, gains social promotion. Selection the predominant cause of the inverted birth-rate. The decay of ruling classes. Contrast with barbarian societies. Heroism and the higher human faculties. The place of social class in human evolution. Analogy of parasitism among ants. Summary.

May it befall that an only begotten son maintain the ancestral home, for thus wealth is increased in a house. HESIOD, eighth century B.C.

History of the theory

WE have seen in the last chapter that among civilized peoples, both in modern and ancient times, an anomalous condition has come into existence, in which the more prosperous social classes, whom we would naturally compare to the successful and well-adapted of an animal species, reproduce their kind considerably more slowly than the socially lower classes. In the ninth chapter we had seen reason to conclude that the innate and heritable disposition has in civilized man a powerful influence upon the rate of reproduction. It is now proposed to show that a logical connexion exists between these two conclusions. It is not denied that what may be called the accidents of history have from time to time determined the social position of various types of men, and have influenced the fertility of various classes. The widespread nature of the phenomenon of the differential birth-rate, existing in great bodies of people, in different nations, and reappearing after long intervals of time in entirely different civiliza- tions, is not, however, to be explained by historical accidents. No explanation of it can be accepted, which does not flow from agencies in almost universal operation, among civilized societies of the most various types.

The theory to be here developed may be found in germ in an interesting observation noted by Francis Galton in the course of his genealogical researches; it has since been extended by several writers, step by step with the advance of our knowledge of the sociological phenomena, but neither its logical cogency, nor its im- portance to sociological theory, seem to have been ever widely grasped, and apart from a few ephemeral papers of my own, and a brief discussion in Major Darwin's recent book The Need for Eugenic Reform, it might be said to have been totally neglected.

In his book on Hereditary Genius, published in 1869, Galton considers the problem presented by the generally acknowledged fact that the families of great men tend, with unusual frequency, to die out. Of thirty-one peerages received by the judges of England, twelve were already extinct. Galton examined the family history of these thirty- one peerages, and lit upon an explanation which he rightly describes as 'Simple, adequate and novel'. A considerable proportion of the new peers and of their sons had married heiresses.

But my statistical lists showed, with unmistakable emphasis, that these marriages are peculiarly unprolific. We might have expected that an heiress, who is the sole issue of a marriage, would not be so fertile as a woman who has many brothers and sisters. Comparative infertility must be hereditary in the same way as other physical attributes and I am assured that it is so in the case of domestic animals. Consequently the issue of a peer's marriage with an heiress frequently fails and his title is brought to an end.

After giving the individual histories of these families he arrived at the following results.

(i) That out of 31 peerages there were no less than 17 in which the hereditary influence of an heiress or coheiress affected the first or second generation. That this influence was sensibly an agent producing sterility in 16 out of these 17 peerages, and the influence was sometimes shown in two, three or more cases in one peerage.

(ii) That the direct male lines in no less than 8 peerages (Galton gives the names in full) were actually extinguished through the influence of the heiresses, and that 6 others had very narrow escapes from extinction, owing to the same cause. I literally have only one case, where the race destroying influence of heiress blood was not felt.

(iii) That out of the 12 peerages that have failed in the direct male line, no less than 8 failures are accounted for by heiress marriages.

Now what of the four that remain. Lords Somers and Thurlow both died unmarried. Lord Alvanley had only two sons of whom one died unmarried. There is only his case and that of the Earl of Mansfield, out of the ten who married and whose titles have since become extinct, where the extinction may not be accounted for by heiress marriages. No one can therefore maintain, with any show of reason, that there are grounds for imputing exceptional sterility to the race of judges. The facts when carefully analysed, point very strongly in the opposite direction.

After drawing similar conclusions from other groups of peers Galton continues :

I tried the question from another side, by taking the marriages of the last peers, and comparing the numbers of the children when the mother was an heiress with those when she was not. I took precautions to exclude from the latter all cases where the mother was a coheiress, or the father an only son. Also since heiresses are not so very common, I sometimes went back two or three generations for an instance of an heiress marriage. In this way I took fifty cases of each. I give them below, having first doubled the actual results, in order to turn them into percentages.

TABLE 11.

Number of sons to each marriage.	Number of cases in which the mother was an heiress.	Number of cases in which the mother was not an heiress.
0	22	2
1	16	10
2	22	14
3	22	34
4	10	20
5	6	8
6	2	8
7	0	4

I find that among the wives of peers 100 who are heiresses have 208 sons and 206 daughters, 100 who are not heiresses have 336 sons and 284 daughters.

The following important paragraphs may also be quoted as showing the weight which Galton attached to this principle.

Every advancement in dignity is a fresh inducement to the intro- duction of another heiress into the family. Consequently, Dukes have a greater impregnation of heiress blood than Earls, and Dukedoms might be expected to be more frequently extinguished than Earldoms, and Earldoms to be more apt to go than Baronies. Experience shows this to be most decidedly the case. Sir Bernard Burke in his preface to the Extinct Peerages states that all the English Dukedoms created from the commencement of the reign of Charles II are gone, excepting 3 that are merged in Royalty, and that only 11 Earldoms remain out of the many created by the Normans, Plantagenets and Tudors. It is with much satisfaction that I have traced and, I hope finally disposed of, the cause why families are apt to become extinct in propor- tion to their dignity chiefly so, on account of my desire to show that able races are not necessarily sterile, and secondly because it may put an end to the wild and ludicrous hypotheses that are frequently started to account for their extinction.

Alphonse de Candolle after noting these remarkable researches, and properly distinguishing between the extinction of the family and that of the male line, reasonably observes that similar conclusions must apply to the rich and affluent classes in general.

La difference do fecondite des heritiercs et non heritieres anglaises est si grande qu'elle avertit d'une cause, jusqu'a present inconnue, du petit nombre des naissances dans les families aisees ou riches, de la noblesse et de la bourgeoisie. En general, les filles riches so marient aisement et selon toutes les probabilites physiologiques, confirmees par les faits que Monsieur Galton a decouverts, ce sont elles qui ont la plus petite chance de laisser des descendants. Leur proportion doit done diminuer Faugmentation de population des classes qui vivent dans Faisance.

Unfortunately M. de Candolle associates this rational explanation of the relative infertility of the upper classes with others such as that of Herbert Spencer, which evidently belong to the category to which Galton had hoped to put an end. Nor is it quite clear that he grasped the point of Galton' s argument, which is not so much that heiresses can marry more easily than other girls, but that they may more reason- ably aim at a marriage which is socially advantageous, and so are liable to mingle their tendencies to sterility with the natural abilities of exceptionally able men.

In a brief but important note contributed in 1913 to the Eugenics Review, J. A. Cobb has given reasons for believing that the case of heiresses, observed by Galton, is but a particular instance of a far more general tendency. Restricting himself to the unconscious causes of relative infertility, Mr. Cobb points out that, just as the fortune of an heiress enables her to make a socially advantageous marriage, so among the children of parents of any class, members of the smaller families will on the average commence life at a social advantage com- pared to members of larger families. Alongside the many excellent qualities which enable a family to improve its social position, relative infertility also plays its part. In this way the less fertile stocks, having the social advantage, will gradually permeate the upper classes of society, and there cause the peculiar situation in which the more fortunate and successful of mankind have the smallest birth-rate.

A quotation from Mr. Cobb's paper will enable the reader to appreciate the point of view from which this important conclusion was reached.

Eugenists agree that the rising generation is largely recruited from the less fit. This is attributed partly to the fact that the upper classes marry later and partly to the fact that apart from the question of post- ponement of marriage the upper classes are less prolific than the lower.

There can be no doubt that at the present time the smaller fertility of the upper classes is almost entirely due to artificial limitation, but there is another cause of their smaller fertility, and it is to this that I wish to direct attention. It is important for the Eugenist to know to what cause he is to attribute this smaller fertility of the upper classes ; if it is entirely due to artificial limitation, which is merely a temporary fashion, the consequences are not likely to be very serious, since the fashion for limiting the family is likely to take the usual course and spread downwards in the community, eventually equalizing the fertility in all ranks of society ; or the fashion may die out altogether when its disastrous effect on the future of the race is perceived. It seems also possible that the advantage of limiting the family will appeal more to the poor than to the rich, for an additional child is a greater burden to the poor, and perhaps eventually the artificial limitation of families will have a beneficial effect on the race by reducing the size of the families of the less efficient.

If, however, as I shall try to show, there is a natural tendency under modern conditions for the more intelligent to become less fertile, the problem is a more serious one.

If variations in fertility are inherited and the wealthier classes have for generations been put through a process of selection by which members of small families have been given an advantage over members of large families, we should expect that the wealthier classes would, as a whole, be less fertile than the poorer classes.

There must be some general cause which prevents the average intelligence in a civilized community from advancing beyond a certain point. That cause seems to me to be the grading of society according to a standard of wealth. This puts in the same class the children of comparatively infertile parents and the men of ability, and their inter- marriage has the result of uniting sterility and ability.

Infertility in all classes, irrespective of its cause, gains social promotion

In the development of the theory by the three writers quoted, it is evident that the progress made has consisted almost entirely in the extension of the application of the principle to a wider and wider range of social classes. This evidently followed merely from the extension of our knowledge of the classes in which an inverted birth- rate manifested itself. Galton was thinking principally of titled families, because he was aware that among these the extinction of the title took place with surprising frequency; De Candolle was aware that a low birth-rate also characterized the rich bourgeois class, and perceived immediately that the principle which Galton had discovered, in the genealogies of titled families, must apply with equal force wherever social position was greatly influenced by inherited capital. It is probable that Cobb was not aware, in 1913, that the results of the census in 1911, in Great Britain, showed that the inversion was strongly developed, even in the poorest class ; but he evidently has no hesitation in believing that it characterized the great mass of the population, and his note has the great merit of applying the principle to classes in which inherited wealth is relatively unimportant. That the economic situation in all grades of modern societies is such as favours the social promotion of the less fertile is clear, from a number of familiar considerations. In the wealthiest class, the inherited property is for the most part divided among the natural heirs, and the wealth of the child is inversely proportioned to the number of the family to which he belongs. In the middle class the effect of the direct inheritance of wealth is also important ; but the anxiety of the parent of a large family is increased by the expense of a first-class education, besides that of professional training, and by the need for capital in entering the professions to the best advantage. At a lower economic level social status depends less upon actually inherited capital than upon expenditure on housing, education, amusements, and dress ; while the savings of the poor are depleted or exhausted, and their prospects of economic progress often crippled, by the necessity of sufficient food and clothing for their children. These obvious facts are corroborated by the arguments upon which the limitation of families is advocated ; of these by far the most weighty is the parent's duty of giving to his children the best possible start in life, and the consequent necessity both of savings, and of expendi- ture an argument at least as forcible for the poor as for the rich.

Selection the predominant cause of the inverted birth-rate

It has been shown in Chapter IX that not merely physiological infertility, but also the causes of low reproduction dependent upon voluntary choice, such as celibacy, postponement of marriage, and birth limitation by married couples, are also strongly influenced by hereditary factors. The inclusion of the hereditary elements responsible for these, to which are certainly due the greater part of the variance in reproduction among civilized men, multiplies many-fold the efficacy of the selective principle at work. We have seen in particular that hereditary differences in the mental and moral quali- ties affecting reproduction, must be of such a magnitude as to produce considerable evolutionary changes, in the course of relatively short historical periods, and that such changes have in fact taken place in the moral temperament of peoples known to have been exposed to the selective action of voluntary family limitation. Consequently it is impossible to avoid the conclusion that, in a society in which members of small families are on the average at a social advantage compared to members of large families, the parents being in other respects equivalent, society will become graded, not only in respect of physiological infertility, but much more rapidly and more steeply graded in respect of those temperamental differences which conduce to celibacy, postponement of marriage and birth limitation.

This inclusive character of the theory when fully developed serves to explain a characteristic of differential reproduction, which would otherwise be quite unintelligible, namely that all the sociological factors into which differential reproduction can be analysed, alike exert their influence in the same direction. If any single sociological cause favoured contraceptive practices in the upper classes, as, for example, freer access to medical knowledge might be supposed to do, the effect to be expected would be a lower birth-rate to parents of a given age, partially compensated in the statistical aggregate by greater readiness to marry. -Equally, if something inherent in the occupational conditions of the better-paid classes were supposed to induce more frequent postponement of marriage, this cause, acting alone, would be naturally accompanied by an increased birth-rate of those married in the higher age groups. What is actually observed, however, is the concurrence in the more prosperous classes, of in- creased celibacy, of higher age at marriage, and of a lower birth-rate of married persons of a given age ; and this we should expect if the effective cause of the phenomenon were the selective promotion into higher social strata of net infertility as such, irrespective of the psychological causes which have induced it.

It is possible to test in another way whether hereditary influences supply a major and controlling cause of the differential birth-rate, or a minor and subsidiary one. Even in Galton's time many causes had been suggested for the portion of the phenomenon then known, ascribing the differences in fertility to differences in social environ- ment, or to some assumed physiological connexion between infertility and the powers of the mind. Since then the list of suggestions has increased: they may be exemplified by, excess of food, which the upper social classes are presumably supposed to consume ; excess of leisure ; the stress of brain work ; the enervating influence of comfort. However baseless the supposed causes may appear to be when each is examined in detail, it is certainly possible a priori, that there might be some subtle influence, of the social environment of the more prosperous classes, really unfavourable to reproduction. The sharpest possible test between the two views would be to ascertain the relative fertilities, among men of a given social class, of those who had risen rapidly in the social scale as opposed to those who were born in that class. For, on the theory that we have to do principally with heritable factors affecting fertility, the fertility of the upper social classes must be prevented from rising by the lower fertility of those whom social promotion brings into their ranks ; the stream of demotion of the more fertile members of the upper classes being relatively a very feeble one. Consequently, the groups enjoying rapid social promotion should, on this theory be even less fertile than the classes to which they rise. If, on the contrary, the important causes were any of those to be included under 'social environment', we should confidently expect the families who rise in the social scale to carry with them some measure of the fertility of the classes from which they originated. We have seen that the differential birth-rate is strongly developed in the United States, and a test is therefore afforded by a table given by Huntington and Whitney of the average number of children per person in the American Who's Who, when the persons are subdivided according to the education they received. They are given in descend- ing order.

TABLE 12.
Estimated children per Kind of education. person.
College and Professional 2.4
College and Ph.D. 2.3
College 2.3
Normal, Business, Trade, Secretarial 2.3
Highschool 2.1
Elementary schools and home 2.1
Professional school only 1.9

As the total number of persons dealt with is about 25,000 the trend of these averages cannot possibly be ascribed to chance ; the table appears to show unmistakably, that among Americans who attain a sufficient level of eminence to be included in Who's Who, those whose social promotion has been most striking have, on the average, fewer children than those whose social promotion has been less. Such a result would appear inexplicable on any of the views that connect the differential fertility of different classes with elements in their social environment, and is a striking confirmation of one of the most unexpected consequences of the theory that the dominating cause lies in the social promotion of the relatively infertile.

Whitney and Huntington give also the results of another inquiry which bear upon the same problem. They have studied the average abilities shown by Yale students coming from families of 1, 2, 3 and up to 6 or more. They find, in general, that the average ability rises as we pass from families of one, to families of two, and so on up to the largest families. This, of course, is not at all what we should expect to find, either in England or America, if we were to test the sons of the population at large. In the population generally, the classes which furnish the largest families would certainly show the lowest average scores, whether we took a scholastic, an athletic or an intelligence test. The Yale students, however, are the sons of a selected group of the population, of persons who can afford to give their children an expensive education. This basis of selection favours the more prosperous parents, who, in so far as their prosperity is due to innate causes, will be innately abler than the general population ; but this selection of parental prosperity will be much more stringent for the parents of six or more children than for the parents of one only. Remembering that the only child may be expected to have a better start in life ceteris paribus than the member of a family of six, we may perhaps expect to find at Yale the only children of less suc- cessful parents educated at equal expense and side by side with the children of the more stringently selected parents, who are able, with families of six or more, still to send them to Yale.

It is in fact a necessary consequence of our theory of the social selection of fertility, that, whereas in the population at large fertility must become negatively correlated with such characters as intelli- gence, which conduce to social promotion, yet, if we could select a group of children about to enter the world with absolutely equal social opportunities we should find, within this group, fertility positively correlated with these characters. For parents who can give to a large family a certain level of educational advantage, could certainly have launched a smaller family with greater advantages, and must therefore possess a higher average level of qualities, apart from fertility, favourable to social promotion, than do the parents of smaller families whose children are actually receiving the same advantages.

I believe no investigation has aimed at obtaining a group in which the educational advantages provided by the parents are completely equalized, but the effect of a partial equalization, in raising the cor- relation between fertility and intelligence, is shown by some interest- ing data published by H. E. G. Sutherland and Godfrey H. Thomson in 1926. In an unselected group of 1924 elementary school children of the Isle of Wight, between the ages of 10 \ and \\\ years a correla- tion coefficient, - 0-154, with a probable error 0-023, was obtained. Since the correlation is negative and clearly significant, it appears that, with this unselected group the least intelligent children belong to the largest families. On the other hand 386 boys of the Royal Grammar School, Newcastle -on-Tyne, the intelligence quotients of which are stated to be very reliable, and 395 boys and girls of Moray House School, Edinburgh, show correlations - 0-058 0-04, and - 0-075 + 0-034 both of which, though still negative, are insignificant in magnitude. Since within the same school, even if of very definite class, much variation must exist in the social advantages with which different pupils enter life, these data leave little doubt that in a group in which these advantages were strictly equalized the correlation between fertility and intelligence would have been raised to a positive value. It is obvious that such results are opposed to any theory which implies a physiological opposition between fertility and intelligence, and are unintelligible upon the view that class differences of fertility are derived wholly or indeed largely from class environ- ment.

The decay of ruling classes

The fact of the decline of past civilizations is the most patent in history, and since brilliant periods have frequently been inaugurated, in the great centres of civilization, by the invasion of alien rulers, it is recognized that the immediate cause of decay must be the degeneration or depletion of the ruling class. Many speculative theories have been put forward in explanation of the remarkable impermanence of such classes. Before proceeding further it may be as well to consider what elements of truth these suggestions may contain.

The Comte de Gobineau, to whose active mind the decline of civilizations presented itself as the greatest of human problems, believed that the disappearance of the original aristocracies was universally due to race mixture. Others have not hesitated to ascribe the infertility of the upper classes to inbreeding ; but since this view is now, on the biological side, universally discredited, it need not be further considered. There was, on the other hand, nothing in Gobineau's theory of the effects of race mixture which could have been disproved by the science of his time ; if the progress of genetical knowledge has rendered his views unlikely they would still have claims to acceptance on an historical basis, were they the only avail- able explanation of the historical facts.

The general consequences of race mixture can be predicted with confidence, without particular knowledge of the factors in which the contrasted races differ. If the races and their descendants intermarry freely, the factors which are inherited independently will be recombined at random; each person of mixed race will resemble the one parental stock in respect of some factors, and the other stock in respect of others. Their general character will therefore be intermediate, but their variability will be greater than that of the original races. Moreover, new combinations of virtue and ability, and of their opposites, will appear in the mixed race, combinations which are not necessarily heterozygous, but may be fixed as permanent racial characters. There are thus in the mixed race great possibilities for the action of selection. If selection is beneficent, and the better types leave the greater number of descendants, the ultimate effect of mix- ture will be the production of a race, not inferior to either of those from which it sprang, but rather superior to both, in so far as the advantages of both can be combined. Unfavourable selection, on the other hand, will be more rapidly disastrous to a mixed race than to its progenitors. It should of course be remembered that all existing races show very great variability in respect of hereditary factors, so that selections of the intensity to which mankind is exposed would be capable of producing rapid changes, even in the purest existing race.

It does not seem unreasonable to conjecture that within each of the great divisions of mankind, internal adaptations or adjustments, between the different faculties of the mind and body, have been established during the long ages of selection under which these races were originally formed. If this were true, the crossing of widely different races would disturb this internal harmony and put the mixed race at an initial disadvantage, from which, even under favourable selection, it might take several generations to recover. The theory of Gobineau depends upon the effect of intermixture of a ruling aristocracy, which Gobineau invariably traces to the European stock, to whose merits he ascribes the progress and stability of all civilizations, with a mixed and coloured people inhabiting one of the great and ancient centres of population, such as China proper, or the valleys of the Ganges, the Euphrates or the Nile. Apart from his assumption of the racial origin of the rulers, the historical importance of such cases cannot be doubted ; and it is in all respects probable that, as intermixture progressed, the ruling class, in the absence of selection, would entirely change its character ; the qualities by which it had been distinguished would be diffused among those of the more numerous race, and in the absence of native ability, 'could no longer achieve the great results, for which, concentrated in a ruling class, they were originally responsible. Nevertheless, granting that the process of racial diffusion sets a certain term to any civilization which depends upon the virtues of an alien minority, it remains to be explained why great civilizations should be assumed always to rest upon so precarious a foundation. If the peoples of the world's great centres of ancient population are inherently incapable of producing of themselves a great and vigorous civilization, an explanation of so remarkable a fact is certainly required. We cannot reasonably be satisfied by accepting it as an accident, that the great civilizing races should have originally occupied only those regions of the earth, where civilization was for so long unknown.

It has been suggested that the disappearance of ruling races of foreign origin in ancient civilizations was due to the selective influence of the climate. This theory stands in the same position as that of race mixture, in respect of the main criticism to which the latter is exposed. It does not explain why the foreign element should be necessary. Apart from this it certainly appears to be a real factor in the situation. Races exposed to a new climate, and to unfamiliar diseases, are certainly in some cases at a disadvantage as regards their death-rate, and probably also as regards their birth-rate. As are the negroes in centres of population infected with tuberculosis, or Euro- peans in regions suffering from uncontrolled malaria.

In one respect the theory of selection by climate and disease ap- pears to possess an advantage over that of race mixture. If the latter were the only agency at work, the disappearance of the ruling class would be accompanied by a permanent improvement of the natives. The effect of successive conquests should accumulate; so that we should expect that a people, such as the Egyptians, should be reasonably far advanced towards the type of a ruling race. The reverse appears to be the case. The effect of the selective influence of climate and disease, on the other hand, would appear to undo completely the racial benefits of an invasion. Further consideration shows that both agencies acting together would lead to an inter- mediate result, for in the distribution of the hereditary factors, immunity to local diseases would often be combined with the qualities of the immigrants. This consideration suggests that unless selection is directed against the qualities of the ruling race as such, some permanent improvement of the native population is a necessary consequence. On the other hand beneficial selection combined with race mixture would lead to the formation of a race combining the condition of acclimatization with the valuable qualities of the in- vaders. It would seem then, from the history of ancient civilizations in the East, that the rate of reproduction has never permanently favoured the ruling classes. If we consider further that, in any ordered society, the burden of maintaining the population is likely to fall upon the parents, and that the possession of wealth is likely sooner or later to be of social advantage, it is possible to offer a rational explanation, not only of the disappearance of ruling classes of foreign origin, but of the paucity of the necessary types of ability from the indigenous population. It would seem not improbable on this view that in its origin civilization was indigenous, favoured by the natural causes which admit of a dense population ; that the most capable elements of this primitive civilization formed themselves sooner or later into the upper classes, that they were slowly imbued with those factors of heritable disposition which make for a reduced prolificacy ; and that with the consequent development of wholesale social promotion, they were, by a rapidly increasing process, eliminated from the race. Their territory, dowered with immense natural resources, and destitute of a vigorous and united government, became the natural prey of a succession of invaders. Once it is apparent that natural causes sufficiently explain the attenuation of the original rulers, the disappearance of aristocracies of foreign origin raises no new problem. The same agencies which destroyed the founders of a civilization are capable of destroying their successors ; the more easily if the unfavourable action of selection were furthered by race mixture and the influence of climate.

The belief that the mere existence of civilized conditions causes degeneracy among the races which experience them, has been held by many writers, and is strongly supported by the instances of barbarous territories which have received the civilization, and shared the decay, of some more advanced state. The people of Roman Gaul and Britain, originally hardy and warlike, were, during the decay of Roman power, scarcely more capable of supporting and safeguarding their civilization, than were the Romans ; they fell a natural prey to inferior numbers of warlike barbarians, without suffering from a foreign climate, or from intermixture with an inferior race.

No explanation of the manner in which civilization produces this deleterious effect, by reference to the inheritance of acquired characters, can now be regarded as satisfactory ; and in any case it must be doubted if the characters acquired in a state of civilization, which include habits of industry and discipline, in addition to the training of the intellectual faculties, can be regarded as unfitting a people to hold its own. It is said that luxury saps the vigour, and dependence the initiative of civilized peoples, and even if this were the unqualified truth as to the effect upon the individual of civilized life, the first generation of misfortune should restore the vigour, and give unexampled opportunities to the initiative, of a threatened people.

We know that the tide of social promotion throughout the Roman dominion must have flowed rapidly. The demand for men for the Imperial services extended freely to provincials, and in the commer- cial and industrial development of the provinces a large scope was given to the initiative of all, even in their home towns. The upper classes, and especially the wealthier of these, were certainly drawn into the vortex of a cosmopolitan society, recruiting itself extensively from the lower orders. Gauls were admitted to the Senate as early as the reign of Claudius, who first occupied Britain. With these facts in mind it is not surprising that after several hundred years absorp- tion in the Roman civilization, Britain and Gaul showed scarcely greater capacity for resistance than the older provinces. For even if the conquest of Britain was a matter of difficulty to the barbarians, the very possibility of the overthrow of an organized Romano - British society shows that very inadequate use must have been made of the resources of the island.

Contrast with barbarian societies

It appears, then, that the social selection of infertility will characterize all states of society in which (1) distinctions of social class exist ; (2) wealth is influential in determining the social position of an individual or his descendants; and (3) the economic charge of producing the next generation is borne exclusively or principally by the parents who produce them, at least in the sense that they would have been better off had they produced fewer. These conditions are of such wide application that we can have no hesitation in postulating them in all societies, ancient or modern, consisting of individuals co-operating for mutual advantage in a state of law and order. The essentially dysgenic features of the situation may, however, be expressed more aptly by saying that they are implied by the existence of a differentiation of social class in which social promotion, or demotion, is determined by the combination of two different attributes (1) socially valuable qualities, and (2) infertility. It is thus not quite exact to say that the selective agency considered must be dysgenic in any society graded according to wealth; this would imply too wide an application of the principle, for gradations of wealth in the form of the control of material property, and authority over the services of others, would seem to be inseparable from any organization of society whatever.

There have certainly existed societies, though not properly speaking civilized societies, in which the institution of social class was highly developed, in which the power and prestige of the individual rested largely upon his pedigree and kinship, in which these class distinctions were doubtless correlated with personal wealth, and in which, nevertheless, the social advantage lay with the larger families. Since in such societies we should infer from the principle of the inheritance of fertility, and the absence of any countervailing causes, that the fertility of the socially superior should be the higher, and consequently that the powerful evolutionary force, which such difference of fertility has been shown to exert, will be directed towards the increase of the qualities favourable to success in these societies, and to the qualities admired in them, their importance for the study of our theory, and for the evolutionary history of mankind, is very great.

The state of society with which we are here concerned, which may be exemplified by the primitive peoples of Northern Europe, as represented in the Icelandic Sagas, in Tacitus' description of the Germans, and probably in the Homeric poems, by the pre-Islamic Bedouin of the Arabian desert, by many, if not all, of the Turkish and Tartar peoples of the Central Asiatic steppes, and by the Polynesians of New Zealand and Samoa, is characterized by a tribal organization, influenced, or indeed dominated, by the blood feud. All these show a strong feeling for aristocratic or class distinction, and this character, as well as the blood feud, seems to be rather rare among uncivilized peoples generally. For this reason it is convenient to designate this particular type of society by a special term, which shall contrast them with civilized, and distinguish them from the other uncivilized peoples. We may conveniently call them barbarians. This term is the more appropriate in that the examples given, few as they are, include the most important groups of peoples, who have, in the course of history, overrun the great centres of relatively permanent civilization, and to whom the existing organization of society can be traced back in historical continuity.

Different civilized nations, although potentially at war with one another, may yet show essentially the same ideas, and an equivalent development of material civilization. The cultural unity of different barbarian tribes is usually much closer, for they are bound together by common language, and a common oral literature, intermarry much more frequently than can the large aggregates which constitute civilized nations, and frequent the same fairs and festivals for trade, religion or recreation. It is necessary to emphasize this unity of culture because, unlike civilized societies having comparable unity, barbarian peoples recognize private, or more properly tribal war as a normal means for avenging and checking crime. The obligation to avenge a kinsman was felt extremely keenly as a moral duty, to shirk which would be incompatible with self-respect or an easy con- science, or, in Wilfred Blunt 's forcible phrase as 'almost a physical necessity'. The existence of this obligation requires that the tribes of kinsmen to which it applies shall be somewhat sharply defined, and with this obligation follows, of course, the obligation to pay, and the right to share, blood money, or to share in booty. A certain degree of economic communism thus characterizes these kindred groups, so that there is little exaggeration in saying that the economic and the military units in such societies are made to coincide. This is at least a convenient form in which to express the contrast with all civilized societies, in which the interests of the economic unit, consisting of a single individual and his dependents, may differ widely from those of the military unit, consisting of the entire nation to which he belongs. The interests of the kindred group as a whole, whose rights to life and property can only be safeguarded by military preparedness, are of course, in the first degree, founded upon military strength, and consequently, among other qualities, upon the fertility of its members.

Social position in barbarian societies consists partly in differences in kind, partly in differences in degree. A powerful group comprises not only the body of free tribesmen of authentic, or noble, pedigree, but also dependent freemen harboured by the tribe, who may have been outlawed from their own tribes, or be the remnants of tribes too weak to stand by themselves ; further there may be unfree dependents, whose position only differs from that of the slaves of civilized societies, in lacking the protection of civil law, and, on the other hand, in differing but little from their masters in education or standard of living. It is important here that differences in social standing are at least as strongly felt among barbarian peoples, as in civilization, and that it is there based not so much on occupation, as on personal and family prestige. Such differences in prestige are not, however, confined to social distinctions within the tribe, but extend to great differences in the repute and distinction of different kindred groups, according to their exploits and power.

It will be admitted, therefore, that in such barbaric societies as we have described, well-defined class distinctions are combined with a distinct social advantage of the more prolific stocks. Nor can we doubt on independent evidence that the families of the highest repute were in fact the most prolific. The high importance given to pedigree, and the care taken to preserve the names, even of a remote ancestry, is evidence of this; for such care would not generally be taken to preserve the memory of ancestors, if these were on the average less distinguished than their descendants. We can thus understand one of the factors which enables such peoples to base their social system upon blood relationship. This evidence indicates, moreover, not only a higher birth-rate but a greater natural increase, when the death- rate also is taken into account. It may well be suspected that the most eminent families suffered in war the highest death-rate, but in the severe losses which barbarian peoples suffer in times of dearth or enforced migration, the more powerful groups would certainly be at a substantial advantage ; and if, as we have seen, selection would tend to increase their innate fertility above that of the less distinguished groups, it is not surprising that we should be led to conclude that society was derived generation after generation, predominantly from its more successful members.

The most important consequence of this conclusion is that human evolution, at least in certain very ancient states of society, has proceeded by an agency much more powerful than the direct selection of individuals, namely the social promotion of fertility into the superior social strata. In particular, it is important that the qualities recognized by man as socially valuable, should have been the objective of such a selective agency, for it has hitherto only been possible to ascribe their evolutionary development to the selection of whole organized groups, comparable to the hives of the social insects. The selection of whole groups is, however, a much slower process than the selection of individuals, and in view of the length of the generation in man the evolution of his higher mental faculties, and especially of the self-sacrificing element in his moral nature, would seem to require the action of group selection over an immense period. Among the higher human faculties must moreover be counted the power of aesthetic appreciation of, or emotional response to, those qualities which we regard as the highest in human nature. It will aid the reader to weigh the efficacy of the social advantage of fertility in barbarous societies, if we analyse in more detail its re- actions upon a single group of qualities typical of barbarian culture.

Heroism and the higher human faculties

The social ideas of all peoples known to us in the stage of emergence from the barbaric condition are dominated by the conception of heroism, and civilized peoples normally look back to so-called 'heroic ages' in which this conception moulded to an important degree the structure of society. The emotional influence of this idea has been so great, especially through the poetic tradition, that it is difficult to give a technically accurate characterization of the phenomenon without using terms charged with rhetorical associations. The reader must remember that we are not concerned to evaluate heroism either through praise or disparagement, but merely to consider its nature and implications as a sociological phenomenon.

The hero is one fitted constitutionally to encounter danger; he therefore exercises a certain inevitable authority in hazardous enter- prises, for men will only readily follow one who gives them some hope of success. Hazardous enterprises, however, are not a necessity save for the men who, as enemies or leaders, make them so, and the high esteem in which tradition surrounds certain forms of definite im- prudence cannot be ascribed to any just appreciation of the chances of success. In modern times it is obvious that a man with any immoderate heritage of this quality has an increased probability of perishing young in some possibly useful border expedition, besides an increased probability of entering an occupation not easily to be reconciled with family life. It is undeniable that current social selection is unfavourable to heroism, at least in that degree which finds it sweet as well as proper to give one's life for his country. Any great war will reveal, I believe, a great fund of latent heroism in the body of almost any people, though any great war must sensibly diminish this fund. No one will, however, doubt that in respect of prudence, long civilized peoples do differ materially from those races in which the highest personal ambition of almost every man was to win renown through heroic achievement.

An examination of the action of selection in barbarous societies in the tribal condition, reveals the possibility of the selection of the heroic qualities beyond the limits set by prudence, by a method analogous to that used in Chapter VII to explain the evolution of distasteful qualities in insect larvae. The mere fact that the prosperity of the group is at stake makes the sacrifice of individual lives occasionally advantageous, though this, I believe, is a minor consideration compared with the enormous advantage conferred by the prestige of the hero upon all his kinsmen. The material advantage of such prestige in barbarous society will, I think, scarcely be questioned ; it is evident in all the heroic literature ; it is directly evidenced by the deliberate vaunting of tribal achievements by professional poets; equally convincing is the great importance attached to genealogy in all such societies, by which the living boast their descent from the mighty dead. The positive aim before the hero is undying fame, he is therefore bound to all that is of good repute ; to the heroic spirit all material achievements are of lesser importance. Equally important with the phenomenon of heroism itself is the esteem in which it is held.

It is inevitable in a tribal state of society that certain stocks should distinguish themselves above others in the heroic qualities. If we may assume that such qualities do in fact benefit their tribesmen, which benefit can be most readily understood through the effects of prestige, then in a tribal society heroism may become a predominant quality. In this matter sexual selection seems in man to have played a most important role. I do not here specially stress the evidence of the poetic tradition, which, in spite of the reputation of poets for effemi- nacy, insists on associating heroism with true love. I should rather rely on the actual marriage customs of barbarous peoples. It should be emphasized that in such marriages the political element is more in evidence than the romantic, without their being the less dominated by the emotional reactions. A marriage is likely to involve blood feud obligations ; union with a powerful kindred is an essential asset. The corporate tribe is interested in the match, and sexual selection is most powerfully exerted by tribal opinion. The prestige of the con- tracting parties is all-important, and while this is partly personal, it also is largely tribal. The wooer relies upon his reputation even for the decision of the lady herself. Both in the Icelandic sagas and in the pre-Islamic poems, marriages are nearly always prompted by the political aspirations of the parties.

Such sexual selection by public opinion must influence many other qualities besides valour. Beauty, highmindedness and every other highly esteemed quality must be thereby enhanced. Its importance for us is that it influences the esteem in which the group of qualities most closely associated with heroism are held. Just as the power of discrimination of the female bird has been shown to be influenced by sexual selection pari passu with the ornaments which she appreciates, so in a barbarous society, in which the heroic qualities do possess an intrinsic tribal advantage, the power to appreciate and the proneness to admire such qualities will be enhanced, so long at least as reproduc- tion is actually greatest in the predominant families. The reader who will candidly compare the current attitude towards rash actions in any long civilized society with that among the peoples under dis- cussion, will scarcely doubt that the hero-worship of barbarous peoples was in fact a mental attitude which, however useless to modern man, played in their lives a very essential part. Changed conditions which have reversed the advantage of the heroic qualities, have also reversed the advantage of being able to recognize and appreciate them. It is obvious that the barbarous element in the tradition of our culture is that which emphasizes and indeed exag- gerates, the natural inequality of man, whereas the religious and legal elements emphasize his civil equality. From the fact that the bar- barians valued more highly certain qualities of human character, it is a fair inference that they perceived such differences more clearly than do civilized men. Direct evidence on this point is necessarily elusive. On questions on which we are better informed than our ancestors it is easy for us to perceive the evidences of our advantage. If the reverse were the case, it would be easier for our ancestors than for ourselves to point out the difference. The only objective fact known to me relevant to the present issue is that moderns with highly trained powers of appreciation do find in the earliest examples of extant poetry a certain elusive quality in the delineation of character, which gives to such verse a recognizable supremacy in the particular literature to which it belongs.

It is, of course, difficult to distinguish between non-percipience and indifference to the distinctions perceived. The antipodes to the spontaneous choice of emotional passion is exhibited in the account given by Risley of the importance of a University degree in the Bengalese marriage market. The successful candidate who emerges with an M.A. becomes instantly, and in virtue of this alien qualifica- tion, a highly eligible match, and may collect in a few months a series of endowered brides. It would be difficult to decide whether this throwing upon the board of examiners the onus of grading the candidates in sexual selection is due to those personal differences, which still to some extent influence European lovers, being but faintly perceived, or, although perceived, to their being esteemed of much less real importance than the University degree.

Among peoples with a considerable contribution of the barbarous element in their social tradition the predominant non-personal factor in mate selection is social class. Social class may, as we have seen, be best defined as a synthesis of such distinctions as wealth, occupation, and family as influence eligibility in marriage, taking account of these distinctions only in so far as they do in fact influence such eligibility. Historically this distinction of social class is continuous with the political and romantic prestige of the predominant clans. It is thus not an accident that the social ostentation of earlier days should survive most conspicuously in weddings. The attenuation and decay of the sentiment of class distinction is the necessary concomitant of the progressive elimination of those elements of the population which enjoy the higher rank. It will be readily understood, if the supposition is correct that among barbarian peoples the pre- dominant class did in fact enjoy a selective advantage, that aristo- cratic institutions should appear to peoples recently civilized to be based on natural justice.

To summarize the points of sociological importance: (i) A bar- barian people organized in kindred groups and recognizing the blood feud as the principle of social cohesion, can scarcely fail to experience a selection in favour of two qualities on which the success of the kindred group principally depends (a) the public spirited, patriotic, or heroic disposition (b) fertility, (ii) The stratification of society in these two qualities implies a selective advantage of the heroic temperament beyond the optimum advantage ascribable to prudent boldness, by reason of the social advantage of fame or heroic reputation, (iii) The power of recognizing the heroic qualities, and of conscious choice in intermarriage, introduces the dual effect of sexual selection in intensifying both the qualities selected and the communal recognition and appreciation of such qualities, (iv) This selection of the popular emotional response to the heroic qualities has the important effects of (a) stabilizing the foundations of the system by strengthening the existing basis of social cohesion, (b) intensifying the selective advantage ascribable to fame or prestige, (c) increasing the selective advantage of all qualities consciously envisaged in sexual selection, (d) exaggerating the realities of natural inequality by the development of an extreme aristocratic doctrine of hereditary nobility. It is important to notice that such practices as polygamy or servile concubinage are not in any sense primary principles of the system of causes described, but may be grafted into the system in so far as they harmonize with the prestige of the hero, or the fertility of his class. Such practices necessarily decay or are transformed to fulfil a secondary social purpose, such as domestic service, as soon as the main conditions of the system are undermined.

The place of social class in human evolution

The combination of conditions which allows of the utilization of differential fertility for the acceleration of evolutionary changes, either progressive or destructive, seems to be peculiar to man. It requires a social organism, and one which is individualistic in repro- duction. Accessory factors of great importance are the elasticity of effective fertility, introduced by infanticide and other methods of family limitation, and the peculiarly heavy burden of parental care occasioned by the extraordinary long childhood of the human race. Up to a certain stage, which was almost certainly prehuman, the ancestors of man were doubtless solitary animals, and until social life began to be developed their fertility must have been stabilized at or near the optimum appropriate to the requirements of parental care. It is to be presumed that infanticide came to be practised, in consequence of an increasing foresight of impending hardships, at an exceedingly remote period, perhaps early in man's history as a social animal. During the immense period of early social life he appears to have learnt to co-operate with his fellows, probably by sympathy with their expressed emotions, instinctively to shun social opprobrium, and perhaps to improve his chances of posterity by mate selection. The sentiment of preference, seems at least so essential to the sexual instincts of man that it is difficult to doubt that sexual selection was early established in mankind, though it may be that the special conditions experienced by their barbarian ancestors prejudices the opinion of civilized man in this matter. Apart from this factor, the evolution of man in the early social stages must have been directed principally towards the establishment of the characteristics favouring individual survival in the social environment.

At some stage, the period of which it would be useless to conjecture, societies must have come into existence, in which some degree of continuity of social class was ensured by the inheritance of property, privilege, prestige or social function, and in which individual differences in the socially valuable qualities were strongly appreciated, and allowed to contribute towards the assessment of social rank. If these characteristics, perhaps in quite a rudimentary form, were combined with a tribal organization of society, in which the rights of each kindred group were established ultimately upon its military power, so that the most fertile were mingled with the most admired or eminent strains in the predominant clans, a profound change must have come over the speed and direction of evolutionary progress in such societies. The new force acted through, and by means of, man's appreciation of human excellence in his fellow men. This appreciation, both in the social selection, and in the sexual selection which formed a part of it, was doubtless guided, from the first, by the interests of the tribal group, or of society as a whole. Such a process provides the means of relatively rapid evolutionary progress in qualities which subordinate the individual interest to that of others, the evolution of which, merely by the selective elimination of entire societies, would seem to be extraordinarily slow. It has, however, all the dangers noted in the case of sexual selection, of running into extravagance ; for the standards of taste will necessarily be modified, step by step, with the qualities to which preference is given, and it may, indeed, be that some of the virtues which appeal most to our imagination are more of the nature of ornaments than of serviceable moral ideals. Among the qualities which seem to have been extravagantly developed among all barbarian peoples are personal and family pride, and, but for the sharp lessons which must always be learnt in a harsh environment, made harsher by mutual warfare, extravagances of this kind might, it would seem, have become much more common than they are in man's moral nature.

It would be of great interest, if it were possible, to compare the rapidity of progress among barbarian peoples, with that of the decline among the civilized. The variations available for evolutionary changes of a destructive nature must be so much more abundant than those available for progressive changes, that we might expect selective intensities of the same order to take some hundreds, or perhaps a thousand generations, to build up in their perfection attributes of the mind, which ten generations of adverse selection might demolish. It does not appear that there should be any great difference in the selective intensities developed in the two cases, if each were in a steady state. The effect of differences of fertility would be increased in the barbarian condition, and diminished among civilized man, by the direct action of prosperity in favouring repro- duction, and this might seem to make the favourable selection among barbarian peoples more intense than the unfavourable selection among the civilized. Against this should, I believe, be set the fact that, although uncivilized peoples, by practising infanticide, can produce as great a variation in net fertility as can birth limitation in civilized man, yet the selective effect of these differences in fertility must, in a harsh environment, be much diminished by heavier mortal- ity in infancy and childhood, so that the net differences of fertility available may be less. With respect to the action of sexual selection it might be thought that this factor, while accelerating progress among barbarians, must be retarding decay among the civilized. But this is certainly not the case in a society in which the prospects of fertility diminish with social advancement, for in such a society it will, on the average, be biologically advantageous, to make, of two possible marriages, that which is socially the less eligible. Moreover those who are most particular in the choice of a mate will most frequently dimmish their fertility by postponement of marriage or celibacy. Consequently sexual selection must be judged to intensify the speed of whichever process, constructive or degenerative, is in action. The intensity of this influence must, however, be much diminished in the later stages of civilized societies, with the decay of the appreciation of personal differences.

Analogy of parasitism among ants

The reaction of economic causes upon the distribution of fertility in human civilization is so disastrous that we could scarcely expect to find it adequately paralleled in insect societies, for among these an active intercommunal selection appears always to be possible. Never- theless the interpretation put by Forel upon the reaction of the ant Tetramorium cespitum to a rather rare parasitic ant Strongylognathus testaceus is sufficiently apposite to be compared to the human situa- tion. The structure of the parasitic ant suggests that it was formerly a slavemaker, but it is now too feeble to be an effective combatant, and the mixed colonies rely for defence upon the host workers. The parasite neuters, though able to excavate and to feed independently, contribute little or nothing to the structure of the nest, and probably obtain most of their food from the tongues of the hosts. They take no part in the care of the young, even of their own queen, and, being thus apparently a survival useless to their own species, it is not surprising that they are produced in relatively scanty numbers compared to the males and queens, which are very small and produced in abundance. The sexual forms of the host, on the other hand, are relatively enormous, since the queens have to supply the biological capital for founding new and independent colonies. In most cases of ant parasitism the mother of the parasitized community is in some manner or other eliminated, and the parasitism consists in the ex- ploitation of the social instincts of the surviving workers for rearing an alien brood. The case under consideration is peculiar in that it appears to be well established that the host queen continues to live and, in addition to the parasite queen, to lay, in the parasitized colony ; but that in this condition she never produces fertile females, the parasites thus gaining a continual supply of host workers to house, feed, educate and defend them, while the fertile queens issuing from the nest are of the parasite species only. Forel ascribes this remarkable condition to the regulatory or economic instincts of the host workers, for the females and males of the parasite are smaller and less troublesome to nourish. This, he says, is evidently sufficient to induce the host workers to rear them in place of their own enormous queens and males, the larvae of which they therefore undoubtedly devour or neglect, as they do in the case of all that seems to be superfluous.

Whether or not Forel is right in this interpretation, his suggestion illustrates well the effect of economic law, if allowed blindly to act in the regulation of fertility. Since the parasites are found in only a small proportion of the Tetramorium nests, these insects have pre- sumably some defensive instincts, which usually succeed in resisting infestation. In human societies man is his own parasite, a circum- stance which seems to ensure that all civilized societies shall be fully infested.

Summary

In accordance with the theory, developed with successive extensions by Galton, De Candolle, and J. A. Cobb, it is shown that the inversion of the birth-rate is a consequence of two causes which have now been fully demonstrated: (i) The inheritance of the characters, whether physical or psychological, determining reproduction ; (ii) The social promotion of the less fertile. The various theories which have sought to discover in wealth a cause of infertility, have missed the point that infertility is an important cause of wealth.

In the light of this theory we can understand how it is that the more prosperous classes, not only have fewer children when married and at a given age, but that they also tend to marry later in life, and to remain more frequently celibate, than do less prosperous classes. We can understand how it is, although the poorer classes generally have more children than the rich, yet that persons of distinction, who have enjoyed great social promotion, are found to have fewer children than persons of equal distinction who have been less promoted. Again, although among the general population the larger families of the less successful classes produce a negative correlation between the ability of a child, measured in various ways, and the size of the family to which he belongs, yet in selected groups of children, chosen as receiv- ing more equal social opportunities, we should expect to find, as indeed is found, with the Yale students, and to a less degree with some middle -class English schools, that the correlations tend to be raised to a positive value. All these facts would be highly paradoxical upon the view that the differences in fertility were the direct result of differences in social environment.

In the problem of the decay of ruling classes it is shown that neither race -mixture, nor the selective action of climate and disease, would suffice to explain their failure under favourable selection. The causes to which we have traced the inversion of fertility must have been operative in the most ancient civilizations, as in our own, and serve to explain the historical importance of ruling races, through the absence of the proper attributes in the native populations. The same causes ensure an adverse selection acting upon each conquering people in turn.

The decline of barbarian peoples, which have received the civiliza- tion, and shared the decay, of some more advanced state, without suffering from a foreign climate or from intermixture with an inferior race, is intelligible by the social promotion and extinction of their more capable members.

Certain uncivilized peoples characterized by a tribal organization, the blood feud, and the importance attached to kinship and pedigree, exhibit a state of society in which the more eminent are certainly the more fertile, and in which the effects of Natural Selection are greatly enhanced by social and sexual selection. The action of these factors is of particular importance in respect of the qualities recognized by man as socially valuable, which have, in this way, received a selective advantage very much greater than any which could be ascribed to the differential elimination of entire tribes. The group of qualities under- stood by these barbarian peoples as associated with heroism has thus been developed considerably beyond the optimum of individual advantage. The higher mental qualities of man, and especially his appreciation of them, seem to be ascribable to the social selection of this type of society.

The selection in favour of the qualities admired among barbarian peoples was probably almost as intense as that in the opposite direc- tion among the civilized. The destructive effect of the adverse selection on these qualities, must, however, be much more rapid than the process by which they were built up.

If the opinion of Forel be accepted as to the reaction of the host ant Tetramorium Cespitum to its parasite Strongylognathus testaceus the situation established in parasitized colonies bears some analogy to the economic reactions of civilized man towards reproduction. Whereas, however, the majority of Tetramorium nests keep themselves free from parasites, human societies inevitably show the necessary variations to ensure their own infestation.