Homo-Culture; Or, The Improvement of Offspring Through Wiser Generation

by M. L. Holbrook

Darwin believed that the effects of the exercise of any part were transmitted. He says: "We may feel assured that the inherited effects of the use and disuse of parts will have done much in the same direction with natural selection in modifying man's structure of body."

We may say that this belief has been held by the common people, uneducated in science. They not unfrequently get at truths in a rude way long before the scientists do. Many parents tell us their children are strongly influenced by some particular occupation of the mother during pregnancy. So strong is this belief, that many mothers are in our times trying to influence the character of their unborn children by special modes of life, by cultivating music or art, or science, in order to give the child a love for these pursuits.

It is by Herbert Spencer that this has been most ably presented. Indeed, he holds that there is no explanation of evolution without the transmission of the effects of the use and disuse of parts. His words are: "If there has been no transmission of acquired character there has been no evolution."

He also says: "If we go back to the genesis of the human type from some lower type of primates, we see that while the little toe has ceased to be of any use for climbing purposes, it has not come into any considerable use for walking or running. It is manifest that the great toes have been immensely developed since there took place the change from arboreal to terrestrial habits. A study of the mechanism of walking shows why this has happened. Stability requires that the line of direction—the vertical line, let fall from the center of gravity—shall fall within the base, and the walking shall be brought at each step within the area of support, or so near that any tendency to fall may be checked at the next step. A necessary result is that if at each step the chief stress of support is thrown on the outer side of the foot, the body must be swayed so that the line of direction may fall within the outside of the foot, or close to it; and when the next step is taken it must be similarly swayed in an opposite direction, so that the outer side of the foot may bear the weight. That is to say, the body must oscillate from side to side, or waddle. The movement of the duck when walking shows what happens when the points of support are far apart. This kind of movement conflicts with efficient locomotion. There is a waste of muscular energy in making these lateral movements, and they are at variance with the forward movement. We may infer, then, that the developing man profited by throwing the stress as much as possible on the inner side of the feet, and was especially led to do this when going fast, which enabled him to abridge the oscillations, as indeed we see it now in the drunken man. Then there was thrown a continually increasing stress upon the inner digits as they progressively developed from the efforts of use, until now the inner digits, so large compared with the outer, bear the greater part of the weight, and being relatively near one another render needless any swaying of the body from side to side in walking. But what has meanwhile happened to the outer digits? Evidently as fast as the great toes have come more and more into play and the small ones have gone more and more out of play, dwindling for—how long shall we say?—perhaps 100,000 years." In other and simpler words, the great toe of man has wonderfully developed since he began to walk upright. This has been from greater use, and the transmission of the effects of this use to offspring. The small toe has decreased in size proportionately. This we can reasonably infer has been the result of disuse, the effects of which were also transmitted to offspring.

A still more remarkable illustration of the effects of use and disuse is seen in the sense of touch in different parts of the body. Prof. Weber, in his laboratory for experimental psychology, has worked out this difference most minutely. He finds that by taking a pair of compasses, the points of which are less than one-twelfth of an inch apart, the end of the forefinger is not able to distinguish more than one point. Going to the middle of the back we have the least discriminating power in the skin, for the points must be separated two and one half inches before the nerves can decide that there are two. Any one may test this on himself. Between these extremes we have many differences. The end of the nose has four times as great power of discrimination as the forehead. When we come to the tip of the tongue, we find it far excels any part of the body in its power of tactual discrimination, it being twice that of the forefinger. In every case we find there is greatest delicacy of touch in those parts where this sense has been most exercised. The tongue is being constantly exercised on our food, on the roof of the mouth, the teeth, etc. It is rarely idle. There is in man no advantage for his survival, Mr. Spencer asserts, by having such a sensitive tongue. He could get on just as well without it. He regards it as a case where the exercise of a function has exalted it remarkably, and this exaltation has been transmitted to offspring. Natural selection, he thinks, is not sufficient to account for it. Natural selection only preserves those characters which will give their possessor some advantage in the struggle for existence.

Still another argument is drawn from the whale. This monster once lived, it is believed, partly on land, probably on low land near water, and must have been smaller than now. It had hind legs; but since it has lived continuously in the water its tail has so developed as to make a far better organ of locomotion, and the legs have dwindled from disuse, so that now there is only a remnant left, and this is hidden beneath the skin. The tail has become more efficient from use, and this has been transmitted so that all whales are born with well developed tails. The legs have dwindled for want of use until they have almost disappeared; and this effect of disuse has also been transmitted to offspring.

Another illustration is furnished by Havelock Charles, an English surgeon, who has spent much time among the Punjab tribes in India, and studied them anthropologically. His account is given in "The Journal of Anatomy," in a paper on the structure of the skeletons of these people. It appears they have facets on the bones, fitting them for the sitting posture. These do not develop after birth, but are seen in the fetus. It seems hardly possible that these facets could have any other origin except by transmission after being acquired by ages of use of sitting posture.

Another argument is drawn from the coadaptation of parts. We know that the male sheep, likewise the goat, the stag, and the males of many other animals, have large horns. They are supposed to be useful in fighting with rivals in order to secure as large a number of females as possible. Now these large horns require at the same time a greater development of the bones of the head to hold them, also larger and stronger vertebræ of the neck and back, and larger muscles of these parts to maintain and use them effectively. In other words, there must be coadaptation of all the parts, otherwise these larger horns would be an incumbrance and useless. Now, if we accept the theory of the inheritance of acquired characters, this is all simple. The use of the head in butting against other males exercises all these parts simultaneously, and they develop equally and at the same time. If, however, inheritance has no part in the matter, then we must fall back on variation in the germ-plasm and natural selection for an explanation; but it is difficult or, as Spencer says, impossible to conceive of variation producing large and heavy horns on these animals and at the same time coadaptation of all the other parts to hold and use them. Sometimes coadaptation does not take place, as in the common brook crab, familiar to every country boy. Its foreclaws or fingers are out of all proportion to the rest of the leg, and its awkwardness is well known. The lobster is another case. Even in human beings we have instances of non-coadaptation, as where the head and brain are out of proportion to the size of the body, or the reverse. I need not multiply instances.

Now, if acquired characters are transmitted, any system of training which exists for a considerable time must necessarily appear in the structure of the body and in the character. If the training is not in accord with the laws of evolution, it causes the race to deviate from the true line of progress, and by just so much hinder advancement. If, on the other hand, our systems of education conform to correct principles, progress is advanced by them.

Quite recently an entirely new theory has grown up, opposed to Lamarckianism, and the theory of the transmission of acquired characters. It has been before the world little more than a decade and has made remarkable progress, though it is too soon to say it has been established beyond dispute. Prof. Weismann, its author, is well equipped as a biologist to maintain and defend it. I have already stated briefly his theory of heredity, namely, that the germ-plasm is continuous from parent to offspring. This necessitates a remodeling of commonly accepted views, an entire giving up of the Lamarckian belief that use and disuse have their effect on progeny. If the germ-plasm continues from one generation to another, then it must already have been formed, or at least provided for, even before the birth of the parents. They may modify it, through growth and nutrition, but not through exercise of any function. Prof. Weismann went at the demonstration of his views in a thoroughly scientific way by the making of experiments on living animals and the collection of facts. From his experiments it is now pretty well established that wounds and injuries, which he considers to be acquired characters, are not transmitted. No matter for how many generations you cut off the tails of dogs, cats, horses or sheep, the effects of this removal do not appear in the progeny. Most parents have some mark on the body, received in early life, some cut or bruise, some scratch, but their children do not inherit them. The famous experiment of cutting off the tails of mice, for generation after generation, and then breeding from them was one of Weismann's methods of substantiating the theory that acquired character is not inherited. The offspring of these mutilated mice had as long tails as if those of their parents had not been removed. The explanation is, the germ-plasm was not in any way affected by the bodily mutilation. The practice of the Flathead Indian is another case. The children of parents whose heads have been artificially flattened are not affected by it. The small feet of Chinese women, made so by binding them and preventing their growth, may also be mentioned.