Popular Science Monthly/Volume 71/July 1907/The Forms of Selection with Reference to their Application to Man



WHAT is the importance of natural selection in mankind is a question often asked. It is about as often answered without analysis. Put in this very general way, it contains, and confuses, several different questions.

It is alleged that the conditions of life are so much improved by civilization that the struggle for existence is vanishing. Is that struggle, then, the only means of selection? And even if the cruder forms of selection are coming to be of little importance in man—which is doubtless the fact—are there not other kinds of selection still to be considered? It is time to analyze selection and determine its species. Then, when we know the kinds of selection, we may ask, with specific reference to each particular one: What is its importance in the present evolution of man? How far is each kind of selection operative in civilized society?

In our task of classification, let us consider first Darwin's division. By his choice of a name for natural selection, Darwin assigns to nature a work analogous to that of the breeder of domestic animals. Natural and artificial are therefore two kinds or species of selection. The latter species is more definitely named breeder's selection. Thus we obtain a first and provisional classification of the forms of selection as


Natural Selection and Breeder's Selection

This simple classification is of importance, rather for an understanding of the meaning of the term natural selection, as Darwin thought of it, than for our particular purposes. But we need to dwell upon it somewhat, and dispose of it, before attempting a more adequate analysis.

The analogy from which the term natural selection is derived suggests a personification of nature. But natural selection is explicitly contrasted with conscious and personal factors.[1] Nature's action is impersonal and unconscious. It is not choice. Breeder's selection, on the other hand, is consciously directed towards a known and very definite end, the chosen "points." The action of natural selection is no more conscious than is the action of the current of water that separates pebbles from sand. This is the first great difference between natural selection and breeder's selection.

In another respect nature's agency in selection differs fundamentally from that of the breeder. The mode of operation of breeder's selection is positive; that of natural selection is negative. Natural selection eliminates by death the less well adapted members of a species. The better adapted survive and reproduce their kind. It does not matter in what respect they are better adapted. Protection from enemies is achieved in the case of the porcupine by his quills. The deer is saved by fleetness; wild cattle by the herding instinct, and by the effective use of horns and hoofs which that makes possible. No particular sort of quality is favored by natural selection, but those lacking in any respect are cut off. Nature has no plan. The line of evolution may take any direction; only, whatever the direction of improvement, woe to the hindmost. We have already seen that breeder's selection is conscious. That means its action is also positive. Attention is directed to reproducing and further evolving a favored type. The fan-tail pigeon exists because breeder's sought to develop a type with an unusually large number of tail feathers. The fleece of the better breeds of sheep has become fine and long because breeders sought this particular result. Breeder's selection positively favors certain individuals and types. Natural selection is primarily destructive of the inferior. It is negative. Incidentally it allows certain better adapted individuals to survive.

The third difference between natural selection and breeder's selection is that the latter operates directly on propagation, not necessarily by death. In "nature," this is among wild animals, the capacity to survive is the whole story. It may in general be assumed that a wild animal that survives to maturity, and lives through its prime, will reproduce its kind. Though it is the essential point always, propagation is not in general the crucial point with lower animals.[2] Among

domestic animals, on the other hand, mere survival is not enough. Where the breeder intervenes, propagation becomes the critical point. The breeder can use inferior cattle as draft animals. He favors some definite type for reproduction, but rejected individuals are not therefore destroyed. They may be put to some other use. Breeders selection has, as we shall come to see, the character of reproductive selection. What Darwin, for the most part, dealt with as natural selection, we shall find it better to call lethal selection.

The root-idea of natural selection, and of selection in general, is segregation into classes distinguished by differences as regards continued existence of the type. One type is better adapted and survives, another is eliminated. Selection means, etymologically, a picking out and setting apart.[3] It is isolation in breeding. One eminent biologist and evolutionist, Romanes, would substitute this, as the more general term, for natural selection, and would make the latter but a species of isolation. If a superior type is to be evolved and preserved, breeding must be confined to those possessing in high degree the characteristics of that type. The most direct and sure way to isolate the fit and to prevent the propagation of unfit types is to kill off the unfit individuals. This is just what "nature" does. But there are other ways of attaining the same goal.

Darwin never attempted a formal classification of the forms of selection. He does name, and treat at length, one other form besides natural selection, that is, sexual selection. Other kinds, which are of comparatively little importance in subhuman species, he either altogether fails to distinguish or touches only casually. By his use of the term sexual selection, which he contrasts with "ordinary "[4] or natural selection, he does imply that the word selection is, by destiny, if not by established usage, a generic term, to be qualified by an adjective in order to indicate the various species of selection.


The Four Kinds of Selection

We have now come to the distinctive purpose of this essay, that is a classification of the forms of selection having general applicability. I believe that adequate analysis—of course from the point of view of the sociologist, which is at the same time the most general point of view—gives us four species of selection, named as follows:

Lethal selection.
Sexual selection.
Re-productive selection.
Group selection.

These terms, some of which are already familiar, are now to be defined.

Darwin thought of natural selection chiefly as the elimination of individuals by death.[5] This is natural selection in the narrower sense. But it is better to avoid possible ambiguity by giving this kind of selection its distinctive name and separate treatment. It may appropriately be called lethal, that is death-bearing selection. Lethal selection, therefore, operates through the early elimination, or death, of relatively ill-adapted individuals. "Early" is here a relative term. Death operative by way of lethal selection occur either before physical maturity, or soon enough after to affect the amount of reproduction. Such death prevents the propagation of "unfit" characters.

Sexual selection depends on the advantage which certain individuals have over others of the same sex and species in respect of mating, and thus of reproduction.[6] It is due to sexual preferences which favor the mating of certain individuals as against others of the same species, and so cause more reproduction of certain characters than of others; or, in another form, it is due to differences between individuals of the same species as regards power forcibly to appropriate mates. The first of these may well be called aesthetic, and the second, combative, sexual selection. Failure to mate, not failure to survive, is the mode of elimination in sexual selection. The individual must become adapted to the phenomena of sex within the species, as well as to outside "nature." "Selection in relation to sex" has an important part in Darwin's theory of organic evolution.

Among animals it is the relatively passive sex which exercises choice in æsthetic sexual selection, that is, usually the female. Hence the beauty and song of birds are male attributes. In combative sexual selection, on the other hand, the competition takes the form chiefly of actual fighting between rival members of the active sex. There is a difference between this struggle for mates and the "struggle for existence." "Nature, red in tooth and claw" is poetic license. The phrase gives no true notion of the workings of natural selection. The poet is apparently licensed to be inaccurate. The struggle for existence is chiefly a noiseless, inglorious effort to wrest from the environment sufficient food to maintain life. For the rest, some animals prey and others are preyed, upon. It is only in combative sexual selection, however, that bloody combat, which implies a degree of equality of prowess, is the regular thing. It is significant, likewise, that the comparison of nature to a cock-pit uses phenomena, not of natural, but of sexual, selection.

Reproductive selection depends directly on difference in degree of fertility. If any quality is generally associated with a particularly high or low degree of fertility, it is at an advantage or disadvantage due to this form of selection. Reproductive selection is the case of influences bearing directly on propagation, apart from obstacles to mating, in a way relatively to diminish or increase the number of offspring from individuals possessing certain characteristics. The idea of reproductive selection is not developed by Darwin,[7] though it is fully in accord with his general theory and supported by his emphasis on propagation. It has little applicability to the lower animals, but for man it has very great importance.

Differences in ability to procure mates with resulting differences in number of offspring can be distinguished from differential results where the opportunity to mate and reproduce is equal. The former is sexual selection; the latter is reproductive selection. The two are related as pertaining to propagation exclusively, and are contrasted with lethal selection in that they do not involve the question of individual survival. Reproductive selection is a phenomenon of the diverse results of equal opportunities for sexual intercourse. Sexual selection is a matter of obstacles to mating, that is to getting opportunities for sexual intercourse at all. The former rests on differences between individuals as regards degree of reproductivity, granted mating. The latter turns on differences in degree of ability to obtain mates. Though an element of each form may be present in a particular case of selection, the distinction is important, especially in mankind.

In order that the individual shall be "selected" in the fullest sense, he must successfully run a threefold gauntlet. He must live to maturity and enjoy a long and vigorous prime. In obtaining a mate, or mates, he must be as successful as the "best" of his fellows. He must also, equally with the most favored of his species, possess and exercise the power to reproduce his kind and to hand down his characteristics to a numerous progeny. If he fails in the first particular, he is eliminated by lethal selection. If he fails at the second point, his kind is eliminated by sexual selection. If he fails in the third respect, his kind is eliminated by reproductive selection. In all these three particulars his failure need not be absolute, but may be a matter of degree, in which ease the elimination is gradual. He may survive to maturity, but perhaps little beyond that. He may leave offspring that are too few in number as compared with those of his fellows. The critical question always is: Whose descendants are to represent the future of the species? The question is one. But a decision may be rendered at any of several different points.

The three forms of selection so far mentioned apply to individuals. Group selection is recognized by Darwin, though not treated separately, nor by him distinguished from natural selection. Group selection results where a number of individuals act and suffer jointly, whether with conscious purpose or not, in matters affecting their success and survival in competition with other groups.[8] It is selection operating groupwise.

We have distinguished three forms of selection of individuals, over against which is now set group selection. It may appear that we should make a triple division of group selection, as we have of the selection of individuals. It is obvious, however, that the concept of sexual selection is entirely inapplicable. A group does not propagate its kind by a sexual relation with another group. Reproduction, of course asexual, might be predicated of a group. The idea of reproduction, however, as applied to the group, is but an analogy; and where so applied, it is of little or no significance for selection. Eeproduction of its individuals is not reproduction of the group, for the group remains the same while its members change, just as does the body while its component cells die and are replaced by others. The group is thus potentially immortal and does not regularly reproduce itself. Wlien a successful group becomes unduly large, it may divide or send out a "daughter colony," thus, so to speak, propagating itself by fission. But this is a question of size, not of differences in degree of natural reproductivity on the part of groups. As regards the "decease" of such a selectional group, moreover, it comes either by dissolution, that is, by the loosening of its bands and the dropping away of its members, or by their physical death. In the former case selection has not yet completed its work. In the latter case its work has taken an individual form. The ultimate incidence of group selection is always on individuals, affecting them either in the duration of their life or in their reproduction. But the effect is likely to be compound. From which of these two sorts of selection it comes, and how much is from one or the other form, are questions which have little importance from the point of view of the group. Therefore, if it is possible, it is not worth while, to attempt to subdivide group selection into lethal and reproductive forms.

Group selection is logically coordinate with all three of the other forms. In practise, however, taking account of its degree of importance, as well as of the fact that it is not to be subdivided, we may treat it as on the same level with lethal, sexual and reproductive selection, constituting a fourth species.

It is repeating to say that successful reproduction of kind is the essential fact in selection. But the importance of the point is great enough to hear such a repetition. It is significant that Darwin got his idea from the practise of breeders of domestic animals, which is based upon the principle of reproductive selection. Lethal selection is more radical and more incisive in its methods, but death itself operates as a selective agency only through preventing reproduction. Elimination by death after the reproductive period is passed is not selectional. It merely makes more room for the new generation. Lethal selection comes through early death. It is probable that most animals die either when very young and immature or else after considerable reproduction. Survivorship tables for man exhibit the same general phenomenon, that is low mortality at the prime of life. Though we can not know all the possibilities of selection until we distinguish the four modes, they are not independent explanatory principles. All are reducible to effective propagation of kind, to success in leaving offspring. The fate of the individual as such, counts for nothing. For selection, the continuation or destruction of the line of descent is the thing. An individual is important only as belonging to or representing such a line of descent. The "struggle for existence" is only an incident, or a method, in selection. Selective propagation is what is essential.

The classification above presented is made with reference to the needs and point of view of the sociologist. One might well doubt whether the careful discrimination of reproductive selection, which has been attempted, would be at all justifiedly the little scope of application it finds among the lower animals. We know that sexual selection also has but limited applicability, and only to higher forms of life. In strictness, reproductive selection has been the factor that has, on occasion, adaptively increased the fertility of a species, no matter how low in the scale; while natural selection must have been the means of adaptively decreasing such fertility. But this is a minor point. Sexual selection seems to be the nearest that nature comes to admitting reproductive selection as an important factor. As regards domestic animals, also, what the breeder controls is mating rather than strictly and directly reproduction. This case well illustrates the difficulty of sharply discriminating reproductive selection. In man, however, fertility is extremely variable, by nature and through artificial means, so that we must, in man, take account of sheer natality, apart from other selective factors.[9] It is significant that the point of view of the sociologist is, in the matter of selection, more inclusive, and more exhaustive of selective possibilities, than that of the biologist.

In our fourfold classification we have left out the term "natural selection." For its narrower, specific meaning "lethal selection" is decidedly preferable. Might not the older phrase be used as the generic name for all the forms of selection? Usage seems to favor this. "Selection," without a qualifying adjective, is logically the generic term, but is not yet so established as to be unquestionable. Natural selection is therefore convenient as a make-shift or substitute general term. It is familiar, and all the forms of selection do occur in nature. So, despite the implication of Darwin's practise in relation to sexual selection, natural selection might be used roughly for all four classes, though with a saving clause against including such a thing as purposive breeder's selection.


Selection Applied to Man

In the attempt to apply selection to man, clearness of conception has often been lost. Two sorts of mistakes have been made. The complexity of life in civilized society, as compared with the simplicity of nature's conditions, has invited, on the one hand, to extensions of meaning, by which processes have been described as natural selection which are not selection at all. In particular, it has been supposed that segregation by economic or social success is selection. It is rather selective dissociation. This is an important preliminary to selection, but the incidence of the latter may as well be unfavorable as favorable to the survival of those who rise in the social scale.

There are, on the other hand, sociologists who deny that natural selection, meaning by that lethal selection, is of much significance for man. Such are likely to develop and emphasize contrasts between natural selection and what they chose to call "social selection." This is a conception for which the writer finds little use. Social selection should mean selection by society, and since society, unlike "nature," is to some degree conscious and purposive, social selection should mean more or less conscious selection by society. Whatever selection there is of this sort may still be brought under one of our four forms. But there are more, and more important, non-teleological sorts of selection resulting from characteristically social processes. And such phenomena of selection in society are what those who talk of social selection have chiefly in mind. These are provided for in our classification, though in distinguishing types use has been made rather of the method of the selection. To attempt to distinguish forms of selection according to the varieties of selective conditions would give an almost endless list, and the differences would not be of explanatory or scientific importance. We may speak of military or religious or industrial selection if we will, but these are descriptive terms rather than logical categories. This fact has not been perceived by those sociologists who, rightly departing from the rough and ready practise which calls almost anything natural selection, have wrongly gone on to find about as many different forms of selection as there are social institutions and customs.[10]

As regards the scope of selection in general in its application to man, we are now prepared to believe that any influence that bears in any of the four ways enumerated upon the continuance of lines of descent presumably has selective importance. Only on the hypothesis of pure chance distribution of effects can any influence known to affect propagation be declared to be non-selective. The chances against this are infinity to one. No enumeration can cover all possible selective agencies. Every habit, custom and institution of man might well be examined with a view to detecting such effects. Selection must have tremendous importance in human society. It certainly is a central problem, perhaps the fundamental problem and point of departure, for a science of society.

Only the confounding of selection in general with mere lethal selection can explain the opinion that selection is inoperative in human society. Even so, the opinion is not well-considered, for there is much selection by death in civilized man. Lethal selection is not a matter of violent death, or death in struggle. The conception of natural selection as the result of a "free fight"—a bellum omnium contra omnes—has no Justification in any phase of its application. Half the population of many civilized societies, and of course on the whole the weaker half, dies before reaching maturity. In the parts of the United States for which tolerable registration statistics are to be had, at least one third of the deaths are of persons under the age of fifteen. This involves lethal selection.

But lethal selection is not all. The forms and agencies of selection multiply as we pass upwards in the organic series. Hence we might expect a culmination, as regards manifoldness and complexity, in man. It is true that there are fewer births to select from, but the selection may come before birth, and in fact comes so always in the last analysis. And if there is less selection by death in man, there is also less random and indiscriminate destruction of human than of lower animal or plant life. The field for the study of selection in human society is as great and as complex as that in which the biologist works.

Of lethal selection in its application to man, little more need be said. Life-tables and deaths according to age tell the story. Lethal selection is not to be dismissed with the statement that men no longer habitually attack and kill one another, and in civilized states do not die for want of food. Of course selection by the dissolution of the weaker constitutions relates chiefly to physical qualities, but its importance for that is great indeed. Modern improvements in medicine and surgery may check the incisiveness of such action of selection. But they can only lower, not destroy, the standard set for survival. Lethal selection, however, even as regards mere physical qualities, amounts to much less for Occidental civilized man than for any other species of living thing. But some other species of selection are proportionately more important.

A weightier consideration that might appear to make lethal selection of less interest to the sociologist is the fact that it appears hardly to touch what is distinctively human in man's constitution, that is, his mental and moral qualities. But such selection does in fact promote mental stability, so far as the strain and stress of modern life drive men to insanity and death. Alcoholism, too, as is proved by the experience of life insurance companies, and by statistics of occupational mortality, tends to eliminate those who are in this respect deficient in self-control. In various ways the ignorant, the imprudent, and the vicious, tend to destroy themselves.

The effects of sexual selection are much more deeply marked in the organisms of birds than among mammals. The sexes in civilized man, however, show pretty clearly its differentiating influence. The greater strength of the male in man is probably due in part to sexual rivalry. As regards women, on the other hand, their conventional title, the "fair sex," is probably due to something more than mere chivalry or mere flattery. The pretty girl still marries better or earlier than her less "well-favored" sister. It is to be hoped that more important qualities than personal appearance are also favored by sexual selection.

Alfred Russel Wallace, the co-discoverer with Darwin of natural selection, though he curiously enough grudges recognition of it as a factor in the evolution of lower animals, apparently because it involves rather highly developed mentality, sees in esthetic sexual selection on the part of women the great means to the future progress of the human species.[11] With this opinion, the writer can not agree. Marriage is not so much a result of exclusive and exacting "elective affinities" that the relatively ineligible can not solace themselves with those of the other sex who are similarly situated. The approximate equality of sex numbers and the institution of monogamy, which forestalls monopolizing tendencies, leave no considerable class of persons eliminated by lack of opportunity to marry. Postponement of marriage on this account is probably of some influence, but of no great importance. Postponement of marriage and abstinence from it—the latter amounting to more than one fifth in some regions—are probably due to variation in the relative strength of the marital and reproductive tendency more often than to failure to find opportunity to marry. Sexual selection is probably still of some importance in man, though of problematic influence.

Reproductive selection is by far the most important of selective instrimientalities operating in civilized man. Here, and very recently, it has first come to great importance. One sixth and more of marriages in certain portions of civilized society are infertile. And differences in the number of children to a family are still more significant. This absolute or relative infertility must be more or less selective in its incidence. Nerve-racking indulgences and ambitions suggested or elicited by civilized life seem to create physiological conditions unfavorable to reproduction. Still more important is the fact that, with the increase and spread of physiological knowledge, the size of the family is placed under the control of volition, and children are no longer a necessary or to be expected result of sexual gratification. So the wish not to be bothered with children, with the moral traits it implies, leads to elimination. Over-cautiousness and desire to pamper children, on the other hand, resulting in the so-called "two-child system," bring about, though more slowly, the same result. The overcautious in such matters certainly will not "inherit the earth." Conscientiousness on account of transmitting physical weaknesses acts in the same way. Celibacy as a religious observance has probably taken from society some of its gentlest natures.[12]

An average of nearly four children to a family is necessary to keep up the numbers of a population. For a family to have fewer is likely to mean that it will have less representation in the next generation than in the present. Such a family is certainly not holding its own in a country of increasing population like the United States. Hence the plaint of "race suicide," which is in fact never race suicide, but only the self-elimination of a particular section of society. The blood of France may become Breton, but it not at all likely that France will lose its population. The New England stock, which populated the West, is probably now declining in numbers in its old home by deficiency of natural increase.[13] But New England is gaining population. There are always relatively and absolutely fertile elements in society, as well as the relatively infertile. The significant thing is what are their differences as regards mental and moral traits. Is "race suicide" due more to selfishness or to over-caution? Is high fertility due more to improvidence or to the love of children? How far is a high standard of life associated with the most desirable mental traits? Clearly reproductive selection is the most important selective influence in present social evolution.

Men act and suffer jointly. Man is a social animal, and he is such through adaptation. Primitive man, like many lower animals, associates himself with others for mutual protection and support. Hence the strength of tribal attachment and of clannishness. To group selection chiefly is to be attributed capacity for cooperation and those feelings of regard for others on which morality is based. The attachment of mother and child is primeval and of course strongest. But the family, created by the presence of the father, is the earliest persistent, truly social group. Still more characteristically social is the bond of union between grown-up brothers and sisters. Out of kinship grouping has grown the broader, though vaguer and less intense, recognition of fellowship contained in morality. Morality has been called the egoism of the group. When developed and refined, it is much more than that, but it is based upon the instinct that draws men together.

Group selection is probably at its best in primitive man. Bagehot's classic discussion of the evolution of a coercive social organization is an application of group selection. But in modern occidental society the process of individualistic atomization has been carried so far as to threaten the disintegration even of the family. Large family, clan, tribe and village community are gone. There is left little but the individual, or the natural family, and the state. What "groups" there are between the state and the family are largely mere expressions of an appetite for association which finds no other and more important object upon which to exercise itself. And the state is of no importance for group selection. It has become a thing of contrivance and a matter of social psychology. The family is the only group left that is of much selectional importance. Of progressive national states there are too few, in the face of the many questions to be answered, to offer the necessary material. And they interpenetrate by migration in a way to defeat selection groupwise.

Selective dissociation is so closely related to selection, and so often confounded with it, that it requires mention here. There is selective dissociation where individuals of more or less similar traits are segregated from others and put into a special environment of a nature to affect their survival.[14] The incidence of the forms of selection varies with geographical region and social class. The process of dissociation is not directly selection, but only indirectly important as its preliminary.

Economic and social rise has been mentioned as often confused with "survival." Survival it is not, but merely selective dissociation of those possessing traits making for success. It probably means selectional disadvantage, owing to the heavy incidence of reproductive selection on "successful" families.

International migration to a new country is another case of selective dissociation. The American colonists were undoubtedly, on the whole, men of superior initiative and independence of character. Their coming to America made possible the multiplication of their descendants and their kind. Even our present-day immigrants are rather superior in point of energy to those of the same economic condition who remain behind, and they come to an environment presenting greater opportunities.

Urban migration is a notable example of selective dissociation. According to the indications of anthropological and other evidence, it is the more energetic element that migrates from country to city. Under conditions prevailing down into the nineteenth century, cities could not maintain their population by natural increase. Migration to the city then meant subjection to an unusually severe incidence of lethal selection. Our modern sanitary improvements have not yet entirely removed the disadvantage of the city as compared with the country.

We have mentioned selection by society as possible, but not a very important fact. The execution of criminals and their imprisonment, so far as it prevents reproduction, are cases of such selection. In crueller ages, with numerous capital crimes and many executions a year, this may have been an important mode of selection. Now it amounts to little. Perhaps public opinion, also, puts certain members of society under some selective disadvantage.

Francis Galton has proposed that society deliberately undertake the improvement of the human stock.[15] He would have certificates of fitness issued and suggests the giving of marriage portions to girls of superior personal qualities and good family. Such a program of "eugenics" would operate through reproductive selection. It is an interesting proposition, if not very practical. Hitherto the method of evolution has been essentially negative, that is, primarily the elimination of the unfit. Will any human society ever be wise enough positively to map out the line which further evolution shall take? The definition of what is undesirable is much simpler than the definition of what is most desirable.

In the above brief review of the incidence of selection in man, it has been the intention of the writer merely to give examples illustrative and suggestive of the applicability and importance of the different forms of selection for the study of man and his social evolution. An extended treatment of this subject is one of the great desiderata of the science of sociology, the half of which will be the theory of selection in its application to man.

A logical and seemingly very forcible objection to the idea that selection applies to man is contained in the contention that heredity has nothing to do with the higher, which are the distinctively human, qualities in human nature. But the common-sense and practical view id that even the highest intellectual and moral qualities are to some extent inheritable. Men look for family traits not merely in the physical features of children. There is certainly a tendency to the inheritance of insanity, which shows that mind is subject to heredity. It is enough for the purposes of the sociologist if the inheritance of the properly human qualities be only statistically true, that is, true for the mass, though not true of every individual. In fact, this is what we should expect. For a number of reasons variation should be at its best in characteristics distinctively human. Biologically viewed, man is like a domestic animal and is a dominant species, both of which facts imply great variability. There is also approximately unrestricted crossing in mankind. The environment, that is complex civilized society, demands diverse specialized qualities; so that the external conditions favor multilinear evolution. The distinctively human qualities have been latest acquired and are therefore most subject to variation. In man, moreover, as the most socialized of animals, much may be left to imitation and education, that is, to "social heredity," Hence there is less need of a hard and fast physical heredity.

The fact that the line of least resistance in development is the resultant of two sets of forces, internal (variation and heredity) and environmental (selection), must not be allowed for an instant to slip the mind. The interdependence and delicacy of adjustment between these forces increases with the complexity of man's higher, special characteristics. Hence the apparent decrease in the importance of heredity. The distinction between what is innate and what is acquired often hinges on mere ease of enumeration of cases of apparent predominance, or relative independence, of one or the other factor. Or the results are referred to the least easily assumed to be constant factor. Such is in practise man's application of causation. Both sorts of factors are always necessarily operative. It must be granted that proper inheritance is a necessary precondition to the appearance of noble qualities, and this alone concedes the presence and importance of heredity. Both internal constitution and modifications from without are determinants of development and man can no more get along without the right sort of heredity now than ever. Complexity and lack of fixity in development do not remove from the sphere of heredity, though they do mean greater possibilities and greater likelihood of variation. They do also give opportunity for the development of a new set of factors in evolution, the socio-psychical. It can not be too strongly emphasized, however, that these socio-psychic factors are conditioned by their' foundation in the innate qualities and capacities of human nature, that is, in the characters given to men by selection. It may be that the power of heredity is limited short of the powers of evolution and development. But this does not seem to be true for the higher moral qualities, nor for conspicuous intellectual power, though it is perhaps well to add the caution that heredity appears to be not yet thoroughly established for these qualities. But selection itself can make heredity more stable. It would be enough for the most Utopian sociologist if all human beings could be brought up and kept up, by the fixation of heredity, to the present highest level of intellectual power and moral character. So much progress selection may accomplish. Whether it does, depends on the adaptation of human institutions to such remote ends.


The question as to the applicability of natural selection to man can not be satisfactorily dealt with as one simple whole. Here as elsewhere analysis is the necessary instrument of science. By analysis we discover four distinct modes of selection: lethal, sexual, reproductive and group selection. We find, also, that these four forms have very different sorts of applicability in the explanation of man's evolution, past and present. Especially under present conditions it is reproductive selection that most calls for consideration.

In these days "race suicide" is a much talked of subject. There is plenty of occasion for the discussion. But the fact that attracts attention is not rightly called race suicide. Literally interpreted, race suicide is an absurdity. The actual fact that is attracting attention is a phase of reproductive selection. Its importance can hardly be exaggerated. But it can be truly evaluated only as seen in its setting as a phase of a form of selection. The fear of race suicide as a matter of quantity of population is no more valid or justifiable—it is rather far less justifiable—than the contrary and equally unanalytic fear of over-population awakened in Malthus and his followers a century ago. The question is not so much one of quantity, either by excess or deficiency, as of quality of reproduction and of population. It is therefore a question of selection. In this matter of selection in mankind it is doubtless true that "race suicide"—if the term means the self-elimination of certain classes of members of society—now plays the most significant part.

  1. Though requiring such a caveat, Darwin's use of the term "natural selection" is a just and appropriate development in the meaning of the words. A possible wrong first impression is corrected by the most elementary knowledge of the subject. Not as much can be said for the proposed alternative, "survival of the fittest." The "fittest" can not well be further defined than as the fittest to survive. Thus we get back to mere survival. What we need to add to this is the notion of selection. Survival involving selection is the thing of interest to the biologist and sociologist. The word "fittest" is often used as if it meant "best," or at any rate most complex and most highly organized. It is particularly in its application to man that this reading of an ethical connotation into the "survival of the fittest" is to be deprecated.

    The words "natural selection," whatever may have been the force of the objection at the introduction of the term, have now quite lost any suggestion of purpose and choice. Even the single word selection is coming to be used and understood as a generic term for natural selection, breeder's selection, "social selection"—if there be such a thing—and for any other forms of selection.

  2. For some it is in part, that is, in sexual selection.
  3. Selection, by usage, is both the process and the result. And of the parts or aspects of the result, it is both negative (elimination) and positive (survival).
  4. Cf, "Descent of Man," sixth paragraph of Ch. VIII.
  5. He says, for example, natural selection "produces its effects by the life or death at all ages of the more or less successful individuals." "Descent of Man," last paragraph of the section entitled The Male Generally More Modified than the Female, Ch. VIII.
  6. These are Darwin's words, with the significant difference that he says "solely in respect of reproduction." See "Descent of Man," fourth paragraph of Ch. VIII. He thus fails to recognize what is called in this article reproductive selection, for his sexual selection is clearly a different thing.
  7. The name and idea are contributions of Professor Karl Pearson. See his essay "Reproductive Selection" in his "Chances of Death and Other Studios in Evolution"; also "Contributions to the Mathematical Theory of Evolution," III., in the Philosophical Transactions of the Royal Society, Vol. 188, p. 253,
  8. In the choice of terms, I have preferred to name the kind of selection from its characteristic means at the decisive point. But I have not been able consistently to hold to this terminology in the case of group selection.
  9. Perhaps it might be better, for this reason, to use the term "natal selection" for what has been called "reproductive selection," and reserve the latter for general use to cover both sexual and natal forms. But the term "natal" suggests germinal selection, and the idea of selection at birth or soon after would also be brought to mind, which is of course lethal selection.
  10. Lapouge, in his "Les Selections Sociales," perhaps best illustrates this tendency.
  11. See his article, "Human Selection," in the Fortnightly Review, Vol. 54; also Popular Science Monthly, Vol. 38.
  12. Galton notices this selectional influence as early as 1869, in his "Hereditary Genius," though of course without distinguishing it as reproductive selection.
  13. See articles of R. R. Kuczynski in the Quarterly Journal of Economics Vol. XVI.
  14. The term "dissociation" is used by C. C. Closson in articles in the Quarterly Journal of Economics, Vols. X. and XI.
  15. Popular Science Monthly, Vol. 60, article at page 218. He has also brought up the subject before the British Sociological Society. Reports of the discussion are printed in recent volumes of the American Journal of Sociology, as well as in the society's Sociological Papers.