A minor point, but one which should not be overlooked, is that change of season once had, and on the diet of the pre-cibi-culturists still has, a much greater influence than on our own to-day. The food of the former varies from month to month, nay, even from week to week. Thus we find the Californians in the early part of the year eating the bark of trees, then clover, next roots, and about the middle of summer, salmon; after that various kinds of seeds come into season, then manzanita berries and pinon nuts, and finally acorns, while game and vermin of various kinds are consumed throughout the year. There is no such pronounced seasonal rotation of food among communities living in the modern cibicultural age. With the manifold facilities at our disposal for artificially producing, storing, and rapidly conveying food from place to place, we moderns are able to subsist upon much the same kind of food throughout the year. Butcher's meat, birds, fish, bread, rice, milk, cheese, butter, eggs, sugar, and some vegetables - e.g. potatoes - are available at all seasons. It is only in respect of highly perishable vegetable foods, such as green vegetables and certain fruits, that the influence of season makes itself decidedly felt, and this influence is every year becoming less and less, as new methods of storage are devised and more rapid means of transit provided.
We can now summarize some of the more important practical truths which the study of man's dietetic past teaches us.
1. The fact that man has evolved from the ape on a highly carnivorous diet at once disposes of the contention so constantly put forward by the unreflecting, that he is essentially vegetarian by nature, and that "meat" and other animal foods are necessarily harmful to him. Doubtless there are some who cannot tolerate meat, and to whom a diet largely, if not entirely, vegetarian is the most suited, but such persons are exceptional, and it may be added subnormal, in respect of digestion and metabolism. "Meat" and other kinds of animal food are often credited with being the cause of ill-health when the saccharide constituents of the diet are equally, if not more, responsible, for in many cases in which improved health follows upon the curtailment of animal food an equally good, perhaps even a better, result could be obtained by cutting down the saccharides. Again, it is often contended that centenarians owe their great age in large measure to the fact of their having always eaten sparingly of meat, whereas it will generally be found that they have been just as moderate in regard to the other items of their food - indeed, that they have observed moderation in most things.
2. The fact that right up to the beginning of the agricultural period man's supply of sugar was scanty, whereas during it and especially within recent times, it has been enormously increased, suggests that ill-health may often result from its excessive consumption. Experience proves this to be the case; we are often able to effect great improvement in health simply by reducing the intake of sugar.
3. Since in pre-cookery times practically all the starchy food had to be laboriously masticated in order to break up the non-digestible cellulose portion, any starch ingested underwent thorough insalivation, with the result that it was to a large extent digested in the mouth and only a small quantity entered the stomach in the crude form. At the present time, owing to the combined influences we have seen at work, not only is the proportion of starch in vegetable food much higher than it used to be - some foods consisting, indeed, of practically pure starch - but this substance is for the most part consumed in a form so soft that it slips into the stomach without having undergone any buccal digestion whatever. As a result the stomach is apt to be burdened with an excess of crude starch leading to disturbance of digestion, disorder of the blood, and impairment of nutrition.
4. The facts that within recent times the supply of vegetable food has increased more than that of animal food, that the softness of modern vegetable food favours its excessive consumption, and that enormous quantities of pure sugar are accessible, prepare us for the conclusion that the neo-man is more likely to suffer from an excess of highly saccharide vegetable food than from an excess of animal food. As a matter of experience we can, on the whole, do more good by curtailing saccharides than by cutting down animal food, and this even in such diseases as gout and megrim.
5. Animal and vegetable food stand in sharp contrast as regards the need of mastication. In the raw state the former does not require any mastication while the latter needs a great deal. The carnivora do not masticate their food; their teeth are adapted to tear flesh and crush bone, and are prevented by their shape from executing the lateral movements necessary to mastication. On the other hand, all the herbivora masticate their food laboriously, with the object, there can be no doubt, of breaking up its cellulose constituents. In the case of the ruminants food which has been swallowed is actually regurgitated for the purpose of being re-chewed at leisure, so essential in their case is efficient mastication to proper digestion.
Again, the effects of cookery on animal and on vegetable food are opposite as regards the need of mastication. By coagulating the albumen of animal tissue cooking may so harden it as to make mastication necessary; whereas by rupturing the non-digestible cellulose compartments of vegetable food (and thus liberating the contained starch, etc.), and also by its softening influence, cooking largely does away with the mechanical need of mastication. Hence cooked vegetable foods, especially the softer varieties, can be, and often are, swallowed without any more than a pretence at mastication, with the result that the jaws are not properly exercised nor the starch properly insalivated. We should therefore insist that some at least of the vegetable food, especially during the years of development, should be taken in forms which compel adequate mastication, such as stale bread, bread-crusts, and hard biscuits. Only in this way will opportunity be afforded for the normal masticatory instinct to develop, an instinct too often stifled at its birth by the prevalent system of pap-feeding.
6. The fact that during the entire period of his evolution from the simian man's vegetable food was eaten raw, whereas at the present time almost the whole of it is cooked, suggests that good may often result from increasing the proportion of raw vegetable food, such as apples, bananas, nuts, and salads, all of which should be thoroughly masticated.
7. The fact also that our vegetable food is so very much more concentrated now than it was in the time of our ancestors suggests the advisability of including a due proportion of bulky vegetable foods in our dietary.
8. The food of primitive man was simple, consisting of animal and vegetable tissues in their natural state; in other words, it was not subjected to elaborate processes solely for the purpose of pleasing the palate. Though it is not desirable on this point, any more than on any other, to aim at a rigid simplicity, yet the ideal dietary is in the main a simple one.
.9. Before the period of fixed agriculture the quantity of food was not in excess of physiological requirements, for though primitive man doubtless had his bouts of gourmandizing, he also had his intervals of enforced starvation; moreover the constant food quest entailed an active mode of life which rendered chronic over-eating impossible. There might be abundance of game, but it had to be hunted; the rivers might teem with fish, but the fish had to be caught; seeds and roots might be plentiful, but they had to be gathered. Hence, though in seasons of plenty primitive man may have grown plump, obesity was practically unknown. These considerations suggest that though man is none the worse, and may, indeed, be all the better, for occasional dietetic indulgence, strict moderation in eating is the ideal to be aimed at.
10. The fact that man is descended from an ancestry whose diet has for long ages varied considerably throughout the year in all temperate latitudes, helps to explain the evil effects of monotony in diet, and emphasizes the importance of introducing variety into it.
11. It is evident from a study of his dietetic past that the digestive system of man is highly adaptable, and that consequently his dietary is not stereotyped as it is for the most part in the case of the lower animals, but is capable of being modified to an almost unlimited extent.
To put briefly the chief lessons to be learnt from man's dietetic history : The ideal dietary should be simple in quality and moderate in quantity. It should contain a certain proportion, say from a quarter to a third, of animal food. Animal food requires little chewing; most raw vegetable food, and all cooked starchy foods require a great deal. Hence it is advisable to give most of the starchy foods in a form compelling vigorous mastication, and a certain proportion of vegetable food should be consumed uncooked. Care should be taken to guard against an excess of sugar. The diet should not be monotonous. Water should be the staple drink and should not be taken with food.
But while these are safe general rules it must not be forgotten that marked dietetic idiosyncrasies are met with, and that men individually display considerable adaptability as regards different kinds of food. Hence it is not possible to attempt the construction of a stereotyped dietary for man, nor if it were would it be advisable, since his dietetic adaptability is an advantage to the race.