Part 29

But now, in conclusion, let us briefly consider the great difficulty of the theory that man is descended from some ape-like, arboreal, speechless animal,—the difficulty of bridging over the wide gap which confessedly separates the lowest race of savages from the highest existing race of apes. After all that has been done to diminish the difficulty, it remains a very great one. It is quite true that what is going on at this present time shows how the gap has been widened, and therefore indicates how it may once have been comparatively small. The more savage races of man are gradually disappearing on the one hand, the most man-like apes are being destroyed on the other,—so that on both sides of the great gap a widening process is at work. Ten thousand years hence the least civilized human race will probably be little inferior to the average Caucasian races of the present day, the most civilized being far in advance of the most advanced European races of our time. On the other hand, the gorilla, the chimpanzee, the orang-outang, and the gibbon will probably be extinct or nearly so. True, the men of those days will probably have very exact records of the characteristics not only of the present savage races of man, but of the present races of apes. Nay, they will probably know of intermediate races, long since extinct even now, whose fossil remains geologists hope to discover before long as they have already discovered the remains of an ape as large as man (the _Dryopithecus_) which existed in Europe during the Miocene period;[40] and more recently the remains of a race of monkeys akin to Macacus, which once inhabited Attica. But although our remote descendants will thus possess means which we do not possess of bridging the gap between the highest races of apes and the lowest races of man, the gap will nevertheless be wider in their time. And tracing backwards the process, which, thus traced forward, shows a widened gap, we see that once the gap must have been much narrower than it is. Lower races of man than any now known once existed on the earth, and also races of apes nearer akin to man than any now existing, even if the present races of apes are not the degraded descendants of races which, living under more favourable conditions, were better developed after their kind than the gorilla, chimpanzee, orang, and gibbon of the present time.

It may be, indeed, that in the consideration last suggested we may find some assistance in dealing with our difficult problem. It is commonly assumed that the man-like apes are the most advanced members of the Simian family save man alone, and so far as their present condition is concerned this may be true. But it is not necessarily the case that the anthropoid apes have advanced to their present condition. Judging from the appearance of the young of these races, we may infer with some degree of probability that these apes are the degraded representatives of more intelligent and less savage creatures. Whereas the young of man is decidedly more savage in character than the well-nurtured and carefully trained adult, the young of apes are decidedly less savage than the adult. The same reasoning which leads us to regard the wildness, the natural cruelty, the destructiveness, the love of noise, and many other little ways of young children, as reminders of a more or less remote savage ancestry, should lead us to regard the comparative tameness and quiet of the young gorilla, for example, as evidence that in remote times the progenitors of the race were not so wild and fierce as the present race of gorillas.

But even when all such considerations, whether based on the known or the possible, have been taken into account, the gap between the lowest savage and the highest ape is not easily bridged. It is easier to see how man _may_ have developed from an arboreal, unspeaking animal to his present state, than to ascertain how any part of the development was actually effected; in other words, it is easier to suggest a general hypothesis than to establish an even partial theory.

That the progenitor of man was arboreal in his habits seems altogether probable. Darwin recognizes in the arrangement of the hair on the human forearm the strongest evidence on this point, so far as the actual body of man is concerned; the remaining and perhaps stronger evidence being derived from appearances recognized in the unborn child. He, who usually seems as though he could overlook nothing, seems to me to have overlooked a peculiarity which is even more strikingly suggestive of original arboreal habits. There is one set of muscles, and, so far as I know, one only, which the infant uses freely, while the adult scarcely uses them at all. I mean the muscles which separate the toes, and those, especially, which work the big toe. Very young children not only move the toes apart, so that the great toe and the little toe will be inclined to each other (in the plane of the sole) nearly ninety degrees, but also distinctly clutch with the toes. The habit has no relation to the child’s actual means of satisfying its wants. I have often thought that the child’s manner of clutching with its fingers is indicative of the former arboreal habits of the race, but it is not difficult to explain the action otherwise. The clutching movement of the toes, however, cannot be so explained. The child can neither bring food to its mouth in this way nor save itself from falling; and as the adult does not use the toes in this way the habit cannot be regarded as the first imperfect effort towards movements subsequently useful. In fact, the very circumstance that the movement is gradually disused shows that it is useless to the human child in the present condition of the race. In the very young gorilla the clutching motion of the toes is scarcely more marked than it is in a very young child; only in the gorilla the movement, being of use, is continued by the young, and is developed into that effective clutch with the feet which has been already described. Here we have another illustration of that divergency which, rather than either simple descent or ascent, characterizes the relationship between man and the anthropoid ape. In the growing gorilla a habit is more and more freely used, which is more and more completely given up by the child as he progresses towards maturity.

Probably the arboreal progenitor of man was originally compelled to abandon his arboreal habits by some slow change in the flora of his habitat, resulting in the diminution and eventual disappearance of trees suited for his movements. He would thus be compelled to adopt, at first, some such course as the chimpanzee—making huts of such branches and foliage as he could conveniently use for the purpose. The habit of living in large companies would (as in the case of the chimpanzee) become before long necessary, especially if the race or races thus driven from their former abode in the trees were, like the gibbons, unapt when alone both in attack and in defence. One can imagine how the use of vocal signals of various kinds would be of service to the members of these troops, not only in their excursions, but during the work of erecting huts or defences against their enemies. If in two generations the silent wild dog acquires, when brought into the company of domestic dogs, no less than five distinct barking signals, we can well believe that a race much superior in intelligence, and forced by necessity to associate in large bodies, would—in many hundreds of generations, perhaps—acquire a great number of vocal symbols. These at first would express various emotions, as of affection, fear, anxiety, sympathy, and so forth. Other signals would be used to indicate the approach of enemies, or as battle-cries. I can see no reason why gradually the use of particular vocal signs to indicate various objects, animate or inanimate, and various actions, should not follow after a while. And though the possession and use of many, even of many hundreds, of such signs would be very far from even the most imperfect of the languages now employed by savage races, one can perceive the possibility—which is all that at present we can expect to recognize—that out of such systems of vocal signalling a form of language might arise, which, undergoing slow and gradual development, should, in the course of many generations, approach in character the language of the lowest savage races. That from such a beginning language should attain its higher and highest developments is not more wonderful in kind, though much more wonderful, perhaps, in degree, than that from the first imperfect methods of printing should have arisen the highest known developments of the typographic art. The real difficulty lies in conceiving how mere vocal signalling became developed into what can properly be regarded as spoken language.

Of the difficulties related to the origin of, or rather the development of, man’s moral consciousness, space will not permit me to speak, even though there were much to be said beyond the admission that these difficulties have not as yet been overcome. It must be remembered, however, that races of men still exist whose moral consciousness can hardly be regarded as very fully developed. Not only so, but, through a form of reversion to savage types, the highest and most cultivated races of man bring forth from time to time (as our police reports too plainly testify) beings utterly savage, brutal, and even (“which is else”) bestial. Nay, the man is fortunate who has never had occasion to control innate tendencies to evil which are at least strongly significant of the origin of our race. To most minds it must be pleasanter as certainly it seems more reasonable, to believe that the evil tendencies of our race are manifestations of qualities undergoing gradual extinction, than to regard them as the consequences of one past offence, and so to have no reason for trusting in their gradual eradication hereafter. But, as Darwin says, in the true scientific spirit, “We are not here concerned with hopes or fears, only with the truth as far as our reason allows us to discover it. We must acknowledge that man, with all his noble qualities, with sympathy which feels for the most debased, with benevolence which extends not only to other men but to the humblest living creature, with his God-like intellect which has penetrated into the movements and constitution of the solar system,—with all these exalted powers, man still bears in his bodily frame the indelible stamp of his lowly origin.” As it seems to me, man’s moral nature teaches the same lesson with equal, if not greater, significance.

_THE USE AND ABUSE OF FOOD._

Francis Bacon has laid it down as an axiom that experiment is the foundation of all real progress in knowledge. “Man,” he said, “as the minister and interpreter of nature, does and understands as much as his observations on the order of nature permit him, and neither knows nor is capable of more.”[41] It would seem, then, as if there could be no subject on which man should be better informed than on the value of various articles of food, and the quantity in which each should be used. On most branches of experimental inquiry, a few men in each age—perhaps but for a few ages in succession—have pursued for a longer or shorter portion of their life, a system of experiment and observation. But on the subject of food or diet all men in all ages have been practical experimenters, and not for a few years only, but during their entire life. One would expect, then, that no questions could be more decisively settled than those which relate to the use or the abuse of food. Every one ought to know, it might be supposed, what kinds of food are good for the health, in what quantity each should be taken, what changes of diet tend to correct this or that kind of ill-health, and how long each change should be continued.

Unfortunately, as we know, this is far from being the case. We all eat many things which are bad for us, and omit to eat many things which would be good for us. We change our diet, too often, without any consideration, or from false considerations, of the wants of the body. When we have derived benefit from some change of diet, we are apt to continue the new diet after the necessity for it has passed away. As to quantity, also, we seldom follow well-judged rules. Some take less nutriment (or less of some particular form of nutriment) than is needed to supply the absolute requirements of the system; others persistently overload the system, despite all the warnings which their own experience and that of others should afford of the mischief likely to follow that course.

It is only of late years that systematic efforts have been made to throw light on the subject of the proper use of food, to distinguish between its various forms, and to analyze the special office of each form. I propose to exhibit, in a popular manner, some of the more important practical conclusions to which men of science have been led by their investigations into these questions.

The human body has been compared to a lamp in which a flame is burning. In some respects the comparison is a most apt one, as we shall see presently. But man does more than _live_; he _works_,—with his brain or with his muscles. And therefore the human frame may be more justly compared to a steam-engine than to the flame of a lamp. Of mere life, the latter illustration is sufficiently apt, but it leaves unillustrated man’s capacity for work; and since food is taken with two principal objects—the maintenance of life and the renewal of material used up in brain work and muscular work—we shall find that the comparison of man to a machine affords a far better illustration of our subject than the more common comparisons of the life of man to a burning flame, and of food to the fuel which serves to maintain combustion.

There is, however, one class of food, and, perhaps, on the whole, the most important, the operation of which is equally well illustrated by either comparison. The sort of food to which I refer may be termed _heat-maintaining_ food. I distinguish it thus from food which serves other ends, but of course it is not to be understood that any article of diet serves _solely_ the end of maintaining heat. Accordingly, we find that heat-maintaining substance exists in nearly all the ordinary articles of food. Of these there are two—sugar and fat—which may be looked on as special “heat-givers.” Starch, also, which appears in all vegetables, and thus comes to form a large proportion of our daily food, is a heat-giver. In fact, this substance only enters the system in the form of sugar, the saliva having the power of converting starch (which is insoluble in water) into sugar, and thus rendering it soluble and digestible.

Starch, as I have said, appears in all vegetables. But it is found more freely in some than in others. It constitutes nearly the whole substance of arrowroot, sago, and tapioca, and appears more or less freely in potatoes, rice, wheat, barley, and oats. In the process of vegetation it is converted into sugar; and thus it happens that vegetable diet—whether presenting starch in its natural form to be converted into sugar by the consumer, or containing sugar which has resulted from a process of change undergone by starch—is in general heat-maintaining. Sugar is used as a convenient means of maintaining the heat-supply; for in eating sugar we are saved the trouble of converting starch into sugar. A love for sweet things is the instinctive expression of the necessity for heat-maintaining food. We see this liking strongly developed in children, whose rapid growth is continually drawing upon their heat-supply. So far as adults are concerned, the taste for sweet food is found to prevail more in temperate than in tropical climes, as might be expected; but, contrary to what we might at first expect, we do not find any increase in the liking for sweet food in very cold climates. Another and a more effective way of securing the required heat-supply prevails in such countries.

As starch is converted into sugar, so by a further process sugar is converted into fat. It is by the conversion of sugar into fat that its heat-supplying power is made available. This conversion takes place in the vegetable as well as in the animal system, and thus fat appears in a variety of forms—as butter, suet, oil, and so forth. Now, precisely as sugar is a more convenient heat-supplier than starch, so fat exceeds sugar in its power of maintaining animal heat. It has been calculated that one pound of fat—whether in the form of suet, butter, or oil—will go as far towards the maintenance of animal heat as two pounds of sugar, or as two pounds and a half of starch. Thus it happens that in very cold countries there is developed a taste for such articles of food as contain most fat, or even for pure fat and its analogues—oil, butter, tallow, dripping, and other forms of _grease_.

I have spoken of starch, sugar, and fat as heat-forming articles of food; but I must note their influence in the development of muscles and nerves. Without a certain proportion of fat in the food a wasting of the tissues will always take place; for muscles and nerves cannot form without fat. And conversely, the best remedy for wasting diseases is to be found in the supply of some easily digestible form of fatty food. Well-fatted meat, and especially meat in which the fat is to be seen distributed through the flesh, may be taken under such circumstances. Butter and salad oil are then also proper articles of food. Cream is still better, and cream cheeses may be used with advantage. It is on account of its heat-supplying and fat-forming qualities that cod-liver oil has taken its place as one of the most valuable remedies for scrofulous and consumptive patients.

But it must be noted that the formation of fat is not the object with which heat-supplying food is taken. It is an indication of derangement of the system when heat-giving food is too readily converted into fat. And in so far as this process of conversion takes place beyond what is required for the formation of muscles and nerves, the body suffers in the loss of its just proportion of heat-supply. Of course, if too large an amount of heat-giving food is taken into the system, we may expect that the surplus will be deposited in the form of adipose tissue. The deposition of fat in such a case will be far less injurious to the system than an excessive heat-supply would be. But when only a just amount of heat-giving food is taken, and in place of fulfilling its just office this food is converted into adipose tissue, it becomes necessary to inquire into the cause of the mischief. Technically, the evil may be described as resulting from the deficient oxygenation of the heat-supplying food. This generally arises from defective circulation, and may often be cured by a very moderate but _systematic_ increase in the amount of daily exercise, or by the use of the sponge-bath, or, lastly, by such changes in the dress—and especially in the articles of attire worn next to the skin—as tend to encourage a freer circulation of the blood. The tendency to accumulate fat may sometimes be traced to the use of over-warm coverings at night, and especially to the use of woollen night-clothes. By attending to considerations of this sort, more readily and safely than by an undue diminution of the amount of heat-supplying food, the tendency to obesity may frequently be corrected.

In warm weather we should diminish the supply of heat-giving food. In such weather the system does not require the same daily addition to its animal heat, and the excess is converted into fat. Experiments have shown that despite the increased rate at which perspiration proceeds during the summer months, men uniformly fed throughout the year increase in weight in summer and lose weight in winter.

So far as mere existence is concerned, heat-forming food may be looked upon as the real fuel on which the lamp of life is sustained. But man, considered as a working being, cannot exist without _energy-forming_ food. All work, whether of the brain or of the limbs, involves the exhaustion of nervous and muscular matter; and unless the exhausted matter be renewed, the work must come to an end. The supply of heat-giving food may be compared to the supply of fuel for the fire of a steam-engine. By means of this supply the _fire_ is kept alive; but if the fire have nothing to work upon, its energies are wasted or used to the injury of the machine itself. The supply of water, and its continual use (in the form of steam) in the propulsion of the engine, are the processes corresponding to the continual exhaustion and renewal of the muscles and nerves of the human frame. And the comparison may be carried yet further. We see that in the case of the engine the amount of smoke, or rather of carbonic acid, thrown out by the blast-pipe is a measure of the vital energy (so to speak) within the engine; but the amount of work done by the engine is measured rather by the quantity of steam which is thrown out, because the elastic force of every particle of steam has been exerted in the propulsion of the engine before being thrown out through the blast-pipe. In a manner precisely corresponding to this, the amount of carbonic acid gas exhaled by a man is a measure of the rate at which mere existence is proceeding; but the amount of work, mental or muscular, which the man achieves, is measured by the amount of used-up brain-material and muscle-material which is daily thrown off by the body. I shall presently show in what way this amount is estimated.

In the composition of the muscles there is a material called _fibrine_, and in the composition of the nerves there is a material called _albumen_. These are the substances[42] which are exhausted during mental and bodily labour, and which have to be renewed if we are to continue working with our head or with our hands. Nay more, life itself involves work; the heart, the lungs, the liver, each internal organ of the body, performs its share of work, just as a certain proportion of the power of a steam-engine is expended in merely moving the machinery which sets it in action. If the waste of material involved in this form of work is not compensated by a continual and sufficient supply of fibrine and albumen the result will be a gradual lowering of all the powers of the system, until some one or other gives way,—the heart ceases to beat, or the stomach to digest, or the liver to secrete bile,—and so death ensues.