We may now rapidly review the chief changes which have taken place in man's diet during the successive phases of his evolution.

1. Relative Quantities Of Animal And Vegetable Food

Our ancestors were mainly vegetarian during the simian and homo-simian stages, but with increasing intelligence they naturally became able to obtain more and more of the much coveted animal food, such as insects, grubs, eggs, and the smaller game, and there took place in consequence a steady rise in carnivorism during these stages (see Fig. 3). With the advent of the early hunting period, and the ability to secure larger game and a considerable quantity of fish, man soon became actually more carnivorous than vegetarian. Then cookery, by increasing the supply of vegetable food, set the tide in the opposite direction, and by the end of the early cookery period man was about equally carnivorous and vegetarian. Thenceforward, with the development of agriculture, he became more and more vegetarian.

2. Increased Concentration Of Vegetable Food

Vegetable food has become increasingly concentrated since the simian era (see Fig. 4). As the evolving man grew in intelligence he became more and more dainty in his choice, discarding the coarser and more bulky kinds in favour of the more concentrated. This was the easier seeing that with his increasing carnivorism he became correspondingly more independent of vegetable food. The introduction of cookery tended in the same direction. It was not, however, until the agricultural period that his vegetable food reached a high degree of concentration. To attain this has, indeed, been the chief object of agriculture. At the present time, when all the food-stuffs - starch, sugar, fat, etc. - are extracted in their pure state from vegetable substances, the process of concentration has probably reached its limit.

the Relative Quantities of Animal and Vegetable Food Consumed during the Various Phases of Man's Evolution.

Fig. 3. - Diagram showing the Relative Quantities of Animal and Vegetable Food Consumed during the Various Phases of Man's Evolution.

The unshaded area indicates the quantity of vegetable food; the shaded area that of animal food.

the Increasing Concentration of Vegetable Food from the Simian Era onwards.

Fig. 4. - Diagram showing the Increasing Concentration (i.e. diminution in bulkiness as represented by the shaded area) of Vegetable Food from the Simian Era onwards.

3. Change In The Consistence Of Vegetable Food

Just as the vegetable food of man has become more and more concentrated, so also has it become progressively softer. Before the adoption of cookery these two changes progressed at equal rate, but from the first employment of that process right up to the present time there has been a progressive abandonment of raw in favour of the softer cooked vegetable food (see Fig. 5). Agriculture, by diminishing the quantity of cellulose in vegetable food, has operated in the same direction. In this present neo-agricultural age the softness of our vegetable food has assuredly reached its limit, for in the first place only a small quantity of raw vegetable food is consumed, and that almost wholly of the comparatively soft cultivated kind, and in the second place the cooked vegetable food is for the most part soft.

the Relative Quantities of Raw and Cooked Vegetable Food consumed during the Various Phases of Man's Evolution.

Fig. 5. - Diagram showing the Relative Quantities of Raw and Cooked Vegetable Food consumed during the Various Phases of Man's Evolution. The shaded area indicates the quantity of raw vegetable food consumed; the unshaded area that of cooked vegetable food.

the Increase in the Quantity of Sugar consumed during the Various Phases of Man's Evolution.

Fig. 6. - Diagram showing the Increase in the Quantity of Sugar consumed during the Various Phases of Man's Evolution.

No attempt is here made to indicate the proportion of sugar to other foodstuffs consumed.

There can be little doubt that dental caries and pyorrhea alveolaris were practically unknown in pre-cookery times. They have increased in direct proportion with the softness of the vegetable food.

4. Increased Consumption Of Sugar

The quantity of sugar consumed has undergone a steady increase from simian times (see Fig. 6). Prior to the agricultural period sugar was derived from honey, the luscious fruits, and to a less extent from other vegetable substances. As the evolving human grew in intelligence we may assume that he secured an ever-increasing supply of luscious fruits, but it was not until he learnt to gather wild honey that he was able to obtain sugar in the pure form. When he first did this we cannot say, but it is not likely that he obtained honey in any quantity until the early hunting period, for the gathering of it demands considerable ingenuity. That he was able to obtain quite large quantities in the early cookery period is evident from our knowledge of extant pre-agriculturists.

With the development of agriculture and the cultivation of such highly saccharine fruits as the date, the fig, the grape, and the banana, man's supply of sugar underwent rapid augmentation, and when he learnt to extract it from the sugar-cane and the beetroot the supply went up by leaps and bounds. At the present time thousands of tons of sugar are annually extracted. In our own country its consumption has within recent years increased enormously.