Are the Effects of Use and Disuse Inherited?

It is often mischievous as well as anomalous in its action. Under civilization with its division of labour, the various functions of mind and body are very unequally exercised. There is overwork or misuse of one part and disuse and neglect of others, leading to the partial breakdown or degeneration of various organs and to general deterioration of health through disturbed balance of the constitution. The brain, or rather particular parts of it, are often over-stimulated, while the body is neglected. In many ways education and civilization foster nervousness and weakness, and undermine the rude natural health and spirits of the human animal. Alcohol, tobacco, tea, coffee, extra brain work, late hours, dissipation, overwork, indoor life, division of labour, preservation of the weak, and many other causes, all help to injure the modern constitution; so that the prospect of cumulative intensification of these evils by the additional influence of use-inheritance is not an encouraging one. It is true that modern progress and prosperity are improving the people in various respects by their direct action; but if use-inheritance has any share in effecting this improvement it must also transmit increased wants and more luxurious habits, together with such evils as have already been referred to. As depicted by its defenders, use-inheritance transmits evils far more powerfully and promptly than benefits. It transmits insanity and shattered nerves rather than the healthy brain which preceded the breakdown. It perpetuates, and cumulatively intensifies, a deterioration in the senses of civilized men, but it fails to perpetuate the rank vigour of various plants when too well nourished, or the flourishing condition of various animals when too fat or when tamed. It already transmits the short-sight caused by so modern an art as watchmaking, but so fails to transmit the long-practised art of seeing (as it does of walking and talking) that vision is worse than useless to a man until he gradually acquires the necessary but non-transmitted associations of sensation and idea by his own experience. In a well-known case, a blind man on gaining his sight by an operation said that "all objects seemed to touch his eyes, as what he felt did his skin" – so little had the universal experience of countless ages impressed itself on his faculties. Under normal healthy conditions use-inheritance is so slow in its action that "several generations" must elapse before it produces any appreciable effect, and then that effect is only precisely what selection might be expected to bring about without its aid. Strong for evil and slow for good, it can convey epilepsy promptly in guinea pigs, but transmits the acquirements of genius so poorly that our best student of the heredity of genius has to account for the frequent and remarkable deterioration of the offspring by a theory which is strongly hostile to use-inheritance. It would tend to make organisms unworkable by the excessive differences in its rate and manner of action on co-operative parts, and by adapting these parts to the total amount of nourishment received rather than to occasional necessity or actual usefulness. It would tend to stereotype habits and convert reason into instinct.

How then can we rely upon use-inheritance for the improvement of the race? Even if it is not a sheer delusion, it may be more detrimental as a positive evil than it is advantageous as an unnecessary benefit; and as a normal modifying agent it is miserably weak and untrustworthy in comparison with the powerful selective influences by which nature and society continually and inevitably affect the species for good or for evil. The effects of use and disuse – rightly directed by education in its widest sense – must of course be called in to secure the highly essential but nevertheless superficial, limited, and partly deceptive improvement of individuals and of social manners and methods; but as this artificial development of already existing potentialities does not directly or readily tend to become congenital, it is evident that some considerable amount of natural or artificial selection of the more favourably varying individuals will still be the only means of securing the race against the constant tendency to degeneration which would ultimately swallow up all the advantages of civilization. The selective influences by which our present high level has been reached and maintained may well be modified, but they must not be abandoned or reversed in the rash expectation that State education, or State feeding of children, or State housing of the poor, or any amount of State socialism or public or private philanthropy, will prove permanently satisfactory substitutes. If ruinous deterioration and other more immediate evils, are to be avoided, the race must still be to the swift and the battle to the strong. The healthy Individualism so earnestly championed by Mr. Spencer must be allowed free play. Open competition, as Darwin teaches, with its survival and multiplication of the fittest, must be allowed to decide the battle of life independently of a foolish benevolence that prefers the elaborate cultivation and multiplication of weeds to the growth of corn and roses. We are trustees for the countless generations of the future. If we are wise we shall trust to the great ruling truths that we assuredly know, rather than to the seductive claims of an alleged factor of evolution for which no satisfactory evidence can be produced.

THE END

1

Which originally appeared in the Nineteenth Century for April and May, 1886.

2

Principles of Biology, § 166, footnote. The English jaws are somewhat lighter than the Australian jaws, though I could not undertake to affirm that they are really shorter and smaller. In the typical skulls depicted on p. 68 of the official guide to the mammalian galleries at South Kensington, the typical Caucasian jaw is very much larger than the Tasmanian jaw, although the repulsively obtrusive teeth of the latter convey the contrary idea to the imagination. Mr. Spencer's assumption that the ancient Britons had large jaws appears to me erroneous. (See Professor Rolleston's Scientific Papers and Addresses, i. p. 250.)

3

Romanes, Galton, and Weismann have made great use of this principle in explaining the diminution of disused organs. Weismann has given it the name of Panmixia, —all individuals being equally free to survive and commingle their variations, and not merely selected or favoured individuals. See his Essays on Heredity, &c., p. 90 (Clarendon Press).

4

Inclusive in each case of fixed strengthening wire weighing about a sixteenth of an ounce or less.

5

References of course are to Factors of Organic Evolution.

6

P. 13; and Nineteenth Century, February, 1888, p. 211.

7

Tomes's Dental Surgery, pp. 273-275. Tomes observes that it is as yet uncertain in what way civilization predisposes to caries. But he shows that caries is caused by the lime salts in the teeth being attacked by acids from decomposing food in crevices, from artificial drink such as cyder, from sugar, from medicine, and from vitiated secretions of the mouth. It is evident that in civilized races natural selection cannot so rigorously insist on sound teeth, sound constitutions, and protective alkaline saliva. The reaction of the civilized mouth is often acid, especially when the system is disordered by dyspepsia or other diseases or forms of ill-health common under civilization. The main supply of saliva, which is poured from the cheeks opposite the upper molars, is often acid when in small quantities. But the submaxillary and sub-lingual saliva poured out at the foot of the lower incisors and held in the front part of the jaw as in a spoon, "differs from parotid saliva in being more alkaline" (Foster's Text Book of Physiology, p. 238; Tomes, pp. 284, 685). One observer says that the reaction near the lower incisors is "never acid." Hence (I conclude) the remarkable immunity of the lower incisors and canines from decay, an immunity which extends backwards in a lessening degree to the first and second bicuspids. The close packing of the lower incisors may assist by preventing the retention of decaying fragments of food. Sexual selection may promote caries by favouring white teeth, which are more prone to decay than yellow ones. Acid vitiation of the mucus might account both for caries and (possibly) for the strange infertility of some inferior races under civilization.

8

Origin of Species, pp. 198-9; Variation of Animals and Plants under Domestication, vol. ii. p. 328 footnote, also p. 206.

9

Mr. Spencer weakly argues that an advantageous attribute (such as swiftness, keen sight, courage, sagacity, strength, &c.) cannot be increased by natural selection unless it is "of greater importance, for the time being, than most of the other attributes"; and that natural selection cannot develop any one superiority when animals are equally preserved by "other superiorities." But as natural selection will simultaneously eliminate tendencies to slowness, blindness, deafness, stupidity, &c., it must favour and improve many points simultaneously, although no one of them may be of greater importance than the rest. Of course the more complicated the evolution the slower it will be; but time is plentiful, and the amount of elimination is correspondingly vast.

10

I venture to coin this concise term to signify the direct inheritance of the effects of use and disuse in kind. Having a name for a thing is highly convenient; it facilitates clearness and accuracy in reasoning, and in this particular inquiry it may save some confusion of thought from double or incomplete meanings in the shortened phrases which would otherwise have to be employed to indicate this great but nameless factor of evolution.

11

Origin of Species, pp. 230-232; Bates's Naturalist on the Amazons. Darwin is "surprised that no one has hitherto advanced the demonstrative case of neuter insects, against the well-known doctrine of inherited habit, as advanced by Lamarck." As he justly observes, "it proves that with animals, as with plants, any amount of modification may be effected by the accumulation of numerous, slight, spontaneous variations, which are in any way profitable, without exercise or habit having been brought into play. For peculiar habits confined to the workers or sterile females, however long they might be followed, could not possibly affect the males and fertile females, which alone leave any descendants." Some slight modification of these remarks, however, may possibly be needed to meet the case of "factitious queens," who (probably through eating particles of the royal food) become capable of producing a few male eggs.

12

Descent of Man, pp. 573, 572, and footnote.

13

Contemporary Review, December, 1875, p. 92.

14

See Origin of Species, pp. 5-8. "Changed conditions induce an almost indefinite amount of fluctuating variability, by which the whole organization is rendered in some degree plastic" (Descent of Man, p. 30). It also appears that "the nature of the conditions is of subordinate importance in comparison with the nature of the organism in determining each particular form of variation; – perhaps of not more importance than the nature of the spark, by which a mass of combustible matter is ignited, has in determining the nature of the flames" (Origin of Species, p. 8).

15

Weismann's Essays on Heredity, &c. Clarendon Press, 1889.

16

Life and Letters, i. p. 16. Darwin's reverence for his father "was boundless and most touching. He would have wished to judge everything else in the world dispassionately, but anything his father had said was received with almost implicit faith; … he hoped none of his sons would ever believe anything because he said it, unless they were themselves convinced of its truth – a feeling in striking contrast with his own manner of faith" (Life and Letters, i. pp. 10, 11).

17

Ibid., i. p. 38.

18

Life and Letters, ii. p. 14.

19

Origin of Species, pp. 117, 118.

20

Ibid., p. 180.

21

Contemporary Review, December, 1875, pp. 89, 93.

22

Variation of Animals and Plants under Domestication, i. 292.

23

Variation of Animals and Plants under Domestication, i. 299-301.

24

To keep pace with this lateral increase in weight, the leg-bones should have lengthened considerably so that their total deficiency in proportional length is 17 per cent., – a changed proportion which being linear is more excessive than the increase of weight by 28 per cent. So marked is the effect of the combined thickening and shortening that in the Aylesbury breed – which is the most typically representative one – the leg-bones have become 70 per cent. heavier than they should be if their thickness had continued to be proportional to their length.

25

This excessive thickening under disuse appears to be due partly to a positive lateral enlargement or increase of proportional weight of about 7½ per cent., and partly to a shortening of about 15 per cent. Carefully calculated, the reduction of the weight of the wing-bones in this breed is only 8·3 per cent. relatively to the whole skeleton, or only 5 per cent. relatively to the skeleton minus legs and wings. The latter method is the more correct, since the excessive weight of the leg-bones increases the weight of the skeleton more than the diminished weight of the wing-bones reduces it.

26

Variation of Animals and Plants under Domestication, i. 284.

27

Variation of Animals and Plants under Domestication, i. 184, 185.

28

Ibid., i. 144, 145.

29

Ibid., i. 185.

30

Variation of Animals and Plants under Domestication, i. 175.

31

Variation of Animals and Plants under Domestication, i. 184. I suspect that Darwin was in poor health when he wrote this page. He nods at least four times in it. Twice he speaks of "twelve" breeds where he obviously should have said eleven.

32

If a prominent breast is admired and selected by fanciers, the sternum might shorten in assuming a more forward and vertical position. If the shortening of the sternum is entirely due to disuse, it seems strange that Darwin has not noticed any similar shortening in the sternum of the duck. But selection has not tended to make the duck elegant, or "pigeon-breasted"; it has enlarged the abdominal sack instead, besides allowing the addition of an extra rib in various cases.

33

Variation of Animals and Plants under Domestication, 144, 175.

34

Variation of Animals and Plants under Domestication, i. 179.

35

In the six largest breeds the shortening of the sternum is nearly twice as great as in the three smaller breeds which remain nearest the rock-pigeon in size. We can hardly suppose that use-inheritance especially affects the eight breeds that have varied most in size. If we exclude these, there is only a total shortening of 7 per cent. to be accounted for.

36

Variation of Animals and Plants under Domestication, i. 183, 186.

37

Variation of Animals and Plants under Domestication, i. 130, 135; ii. 288.

38

Encyclopædia Britannica, article "Zoology."

39

Variation of Animals and Plants under Domestication, ii. 367.

40

Variation of Animals and Plants under Domestication, ii. 367. Why then does the cheetah inherit ancestral habits so inadequately that it is useless for the chase unless it has first learned to hunt for itself before being captured? (ii. 133).

41

Descent of Man, p. 33.

42

Origin of Species, pp. 210, 211.

43

E. S. Delamer on Pigeons and Rabbits, pp. 132, 103. For other points referred to, see pages 133, 102, 100, 95, 131.

44

Origin of Species, pp. 188, 110; Descent of Man, pp. 32-35; Variation of Animals and Plants under Domestication, ii. 289, 293. Use or disuse during lifetime of course co-operates, and in some cases, as in that of the canoe Indians, may be the principal or even perhaps the sole cause of the change.

45

For the importance of panmixia as invalidating Darwin's strongest evidence for use-inheritance – namely, that drawn from the effects of disuse in highly-fed domestic animals where there is supposed to be no economy of growth – see Professor Romanes on Panmixia, Nature, April 3, 1890.

46

Descent of Man, p. 33.

47

Descent of Man, p. 33.

48

Variation of Animals and Plants under Domestication, i., 453.

49

Descent of Man, p. 33.

50

Descent of Man, p. 33.

51

Wallace shows that the changes in our domestic animals, if spread over the thousands of years since the animals were first tamed, must be extremely insignificant in each generation, and he concludes that such infinitesimal effects of use and disuse would be swallowed up by the far greater effects of variation and selection (Darwinism, p. 436). Professor Romanes has replied to him in the Contemporary Review (August 1889), showing that this is no disproof of the existence of the minor factor, inasmuch as slight changes in each generation need not necessarily be matters of life and death to the individual, although their cumulative development by use-inheritance might eventually become of much service. But selection would favour spontaneous variations of a similarly serviceable character. The slightest tendency to eliminate the extreme variations in either direction would proportionally modify the average in a breed. Use-inheritance appears to be so relatively weak a factor that probably neither proof nor disproof of its existence can ever be given, owing to the practical impossibility of disentangling its effects (if any) from the effects of admittedly far more powerful factors which often act in unsuspected ways. Thus wild ducklings, which can easily be reared by themselves, invariably "die off" if reared with tame ones (Variation, &c., i. 292, ii. 219). They cannot get their fair share in the competition for food, and are completely eliminated. Professor Romanes fully acknowledges that there is the "gravest possible doubt" as to the transmission of the effects of disuse (Letter on Panmixia, Nature, March 13, 1890).

52

Variation of Animals and Plants under Domestication, ii. 287-289.

53

Descent of Man, pp. 612, 131.

54

A very able anatomist of my acquaintance denies the inheritance of mutilations and injuries, although he strongly believes in the inheritance of the effects of use and disuse.

55

Variation of Animals and Plants under Domestication, i. 467-469. Lost toes were only seen by Dr. Dupuy in three young out of two hundred. Obersteiner found that most of the offspring of his epileptic guinea-pigs were injuriously affected, being weakly, small, paralysed in one or more limbs, and so forth. Only two were epileptic, and both were weakly and died early (Weismann's Essays, p. 311). A morbid condition of the spinal cord might affect the hind limbs especially (as in paraplegia) and might occasionally cause loss of toes in the embryo by preventing development or by ulceration. Brown-Séquard does not say that the defective feet were on the same side as in the parents (Lancet, Jan., 1875, pp. 7, 8).

56

Variation of Animals and Plants under Domestication, ii. 57.

57

Ibid., ii. 392. Perhaps it might be better to suppose that the best gemmules were sacrificed in repairing the injured nerve, and hence only inferior substitutes were left to take their place, and could only imperfectly reproduce the injured part of the nervous system in offspring.

58

Hence perhaps Mr. Spencer's error in representing the epileptic liability as permanent and as coming on after healing (Factors of Organic Evolution, p. 27).

59

It is not claimed that the imperfect foot was on the same side of the body as in the parent, and where parents had lost all the toes of a foot, or the whole foot, the few offspring affected usually had lost only two toes out of the three, or only a part of one or two or three toes. Sometimes the offspring had toes missing on both hind feet, although the parent was only affected in one. One diseased ear and eye in the parent was "generally" or "always" succeeded by two equally affected ears and eyes in the offspring (cf. Pop. Science Monthly, New York, xi. 334). The important law of inheritance at corresponding periods was also set aside. Gangrene or inflammation commenced in both ears and both eyes soon after birth (pointing possibly to infection of some kind); the epileptic period commenced "perhaps two months or more after birth," while the loss of toes had occurred before birth. In no case, as Weismann points out, is the original mutilation of the nervous system ever transmitted. Even where an extirpated ganglion was never regenerated in the parent, the offspring always regained the part in an apparently perfect condition. On the whole the conflicting results ought to be as puzzling to those who may attribute them to a universal tendency to inherit the exact condition of parents as they are to those who, like myself, are sceptical as to the existence of such a law or tendency.

60

The various results need to be fully and impartially recorded, and they should also be well tested and confirmed in proportion as they appear improbable and contrary to general experience. Professor Romanes has been carrying out the necessary experiments for some time past.

61

Natural History Museum, central hall, third recess on the left.

62

Traité de l'Hérédité, ii. 489; Variation of Animals and Plants under Domestication, i. 469. If injuries are inherited, why has the repeated rupture of the hymen produced no inherited effect?

63

Compare the three cases of crooked fingers given in Variation of Animals and Plants under Domestication, ii. 55, 240.

64

Ibid., i. 460. Thus, where two brothers married two sisters all the seven children were perfect albinos, although none of the parents or their relatives were albinos. In another case the nine children of two sound parents were all born blind (ii. 322).