Nature and Nurture

byJ. Arthur Thomson

We have seen that the scientific position in regard to the transmissibility of modifications should be one of active scepticism, that there seems to be no convincing evidence in support of the affirmative position, and that there is strong presumption in favor of the negative.
A modification is a definite change in the individual body, due to some change in "nurture." There is no secure evidence that any such individual gain or loss can be transmitted as such, or in any representative degree. How does this affect our estimate of the value of "nurture"? How should the sceptical or negative answer, which we believe to be the scientific one, affect our practice in regard to education, physical culture, amelioration of function, improvement of environment, and so on? Let us give a practical point to what we have already said.
a) Every inheritance requires an appropriate nurture if it is to realize itself in development. Nurture supplies the liberating stimuli necessary for the full expression of the inheritance. A man's character as well as his physique is a function of "nature" and of "nurture." In the language of the old parable of the talents, what is given must be traded with. A boy may be truly enough a chip of the old block, but how far he shows himself such depends on "nurture." The conditions of nurture determine whether the expression of the inheritance is to be full or partial. It need hardly be said that the strength of an (inherited) individuality may be such that it expresses itself almost in the face of inappropriate nurture. History abounds in instances. As Goethe said, "Man is always achieving the impossible." Corot was the son of a successful milliner and prosperous tradesman, and he was thirty before he left the draper's shop to study nature.
b) Although modifications do not seem to be transmitted as such, or in any representative degree, there is no doubt that they or their secondary results may in some cases affect the offspring. This is especially the case in typical mammals, where there is before birth a prolonged (placental) connection between the mother and the unborn young. In such cases the offspring is for a time almost  part of the maternal body, and liable to be affected by modifications thereof, e.g., by good or bad nutritive conditions. In other cases, also, it may be that deeply saturating parental modifications, such as the results of alcoholic and other poisoning, affect the germ cells, and thus the offspring. A disease may saturate the body with toxins and waste products, and these may provoke prejudicial germinal variations.
c) Though modifications due to changed "nurture" do not seem to be transmissible, they may be re-impressed on each generation. Thus "nurture" becomes not less, but more, important in our eyes.
"Is my grandfather's environment not my heredity?" asks an American author quaintly and pathetically. Well, if not, let us secure for ourselves and for our children those factors in the "grandfather's environment" that made for progressive evolution, and eschew those that tended elsewhere.
Are modifications due to changed nurture not, as such, entailed on offspring? Perhaps it is just as well, for we are novices at nurturing even yet! Moreover, the non-transmissibility cuts both ways: if individual modificational gains are not handed on, neither are the losses.
Is the "nature"—the germinal constitution, to wit—all that passes from generation to generation, the capital sum without the results of individual usury; then we are freed, at least, from undue pessimism at the thought of the many harmful functions and environments that disfigure our civilization. Many detrimental acquired characters are to be seen all around us, but if they are not transmissible, they need not last.
In the development of "character," much depends upon early nurture, education, and surrounding influences generally, but how the individual reacts to these must largely depend on his inheritance. Truly the individual himself makes his own character, but he does so by his habitual adjustment of his (hereditarily determined) constitution to surrounding influences. Nurture supplies the stimulus for the expression of the moral inheritance, and how far the inheritance can express itself is limited by the nurture-stimuli available just as surely as the result of nurture is conditioned by the hereditarily determined nature on which it operates. It may be urged that character, being a product of habitual modes of feeling, thinking, and acting, cannot be spoken of as inherited, but bodily character is also a product dependent upon vital experience. It seems to us as idle to deny that some children are "born good" or "born bad," as it is to deny that some children are born strong and others weak, some energetic and others "tired" or "old." It may be difficult to tell how far the apparently hereditary goodness or badness of disposition is due to the nutritive influences of the mother, both before and after birth, and we must leave it to the reader's experience and observation to decide whether we are right or wrong in our opinion that quite apart from maternal nutritive influence there is a genuine inheritance of kindly disposition, strong sympathy, good humor, and good will. The further difficulty that the really organic character may be half-concealed by nurture-effects, or inhibited by the external heritage of custom and tradition, seems less serious, for the selfishness of an acquired altruism is as familiar as honor among thieves.
It is entirely useless to boggle over the difficulty that we are unable to conceive how dispositions for good or ill lie implicit within the protoplasmic unit in which the individual life begins. The fact is undoubted that the initiatives of moral character are in some degree transmissible, though from the nature of the case the influences of education, example, environment, and the like are here more potent than in regard to structural features. We cannot make a silk purse out of a sow's ear, though the plasticity of character under nurture is a fact which gives us all hope. Explain it we cannot, but the transmission of the raw material of character is a fact, and we must still say with Sir Thomas Browne: "Bless not thyself that thou wert born in Athens; but, among thy multiplied acknowledgments, lift up one hand to heaven that thou wert born of honest parents, that modesty, humility, and veracity lay in the same egg, and came into the world with thee."