In Lesson 9 we learned that all plant and animal species are in a perpetual state of competition for larger and larger shares of the total flow of energy from sunshine. The number of individuals of a particular animal species that can live in a given area is dependent in part upon the rate at which energy occurs in that area in a form suitable for use by that species; in part upon the number of competing species for energy in the same form; and in part upon the rate at which this same species becomes food, and therefore serves as the energy supply for still other species.

Under the strenuous competition for existence there develops in a given area between the various plant and animal species a state of balance, or, of dynamic equilibrium. This state of balance is precarious and is subject to disturbances by a change of weather conditions and hence of food supply, or it can be disturbed by numerous other factors.

The human species, as we have seen, exists as a part of this dynamic ‘web of life’.

The history of the human species since prehistoric times is distinguished chiefly from that of other animal species in that during this period man has been learning progressively how to deprive a larger and larger share of the sun’s energy from the other animals and direct it into his own uses. This has resulted in the ascendancy of man and has wrought unprecedented havoc among the other animals of the earth.

In our last lesson we saw that the use of a simple tool like a club gave man a decided advantage in the struggle for existence, and by increasing his food supply, made available for man’s use a larger supply of the total flow of the sun’s energy. We saw that the discovery of the use of fire, probably his first use of energy other than food eaten, gave him another decided advantage tending both to increase his length of life and to enlarge the area he could inhabit. The use, both of the club and of fire, tended to increase the human population of the earth.

Domestication of Plants. Let us review a few more of the high points of man’s conquest of energy. Consider the domestication of plants. The first stage in the domestication of plants consists of taking those plants in a wild form which are suitable for food for man or his animals (or otherwise useful, as for clothing) and cultivating them for the purpose of increasing their yield. This cultivation consists chiefly of two things: (1) the removal of competing plants from the area under cultivation; (2) the loosening of the soil to increase the yield of the plants cultivated.

The net effect of this is that a very much greater portion of the solar radiation incident upon the area under cultivation is converted into forms suitable for food for man and his animals, or into other useful products, than was the case prior to such cultivation. The domestication of plants, therefore, is simply an artificial means of diverting a larger and larger proportion of the sun’s energy (which formerly was, as far as man is concerned, wasted) into human usage.

Domestication of Animals. Consider the domestication of animals. Out of all the array of the animal species in regions inhabited by man only certain ones, such as sheep, goats, cattle, and swine, were especially suitable for human food and at the same time amenable to domestication. Others, such as the horse, the camel, the ox, and the dog, were suitable for other uses than food, such as carrying burdens or otherwise performing work.

Here, as in the case of the domestication of plants, we are dealing primarily with a diversion of energy. Prior to the domestication of animals, a given pasture area would have been roamed by the miscellaneous grass eating herds, along with wolves, lions and other predatory animals preying upon these. In such an area man would have taken his chances in competition with the rest. Suppose, however, he domesticated one species of these animals, sheep, shall we say, and protected it from its natural enemies. Under these circumstances the biological equilibrium would be disturbed, and the protected species would multiply out of all proportion to the numbers it would have if not so protected. Because of their great number these domestic herds also would eat a far larger proportion of the grass in the area than they would have been able to do otherwise.

Thus, the domestication of animals is a device whereby man has been able to convert solar energy represented in such vegetation as pasture grass, which is not in that form suitable for human uses directly, into forms such as meat, wool, and skins, which are suitable for human use.

We see, therefore, that the domestication of plants and animals, by beginning with a disturbance of the biological equilibrium between plant and animal species, results in an increased food and clothing supply for man, himself, from a given area. Since, under primitive conditions, the human species tends always to expand faster than these devices tend to increase the food supply, it follows that the astounding result of each of these achievements must have been to increase the number of people who could exist in a given area, and, therefore, to increase the human population of the earth. The population of the Nile Delta during the time of the Egyptians, with their cultivation of plants, must have been vastly greater than the number which could have subsisted in the same area in its wild and undeveloped state.

The North American Continent affords a very interesting contrast of a similar kind. The Indians had few domestic plants, and almost no domestic animals. Their principal tools were fire, the bow and arrow, and the canoe. While the size of the Indian population prior to the European invasion can only be estimated, available figures indicate that the total population north of Mexico at the time of the discovery of America was less than 2,000,000 people. With the methods of energy conversion known to the Indians it is doubtful if the area in which they lived could have supported very many more than actually existed at that time. In other words, there was pretty nearly a state of dynamic equilibrium between the Indians and their food supply. The population of the United States alone is at the present time 131,000,000 people (1940). This has been made possible only by a far greater utilization or conversion of energy, than was possible by the Indians in their state of knowledge.

Discovery of Metals. Succeeding stages in the conquest of energy by the human species are represented by the discovery of metals and their uses. Metals provided better tools and weapons, both of offense and defense, than man had known prior to that time. This still further, in the manner we have indicated, disturbed the biologic balance in man’s favor, and again he extended his conquest and increased his numbers.

Greater mobility also was achieved by the use of the camel and the horse as beasts of burden. Wheeled vehicles were devised, and boats of increasing sizes and improved modes of propulsion were developed. The combination of the use of metals, and the increased mobility brought the human species face to face with some of the hard facts of geology, namely, that metals in concentration suitable for human exploitation occur but rarely and only in certain localities of the earth’s surface. Moreover, the ores of these metals occur at various depths beneath the earth’s surface and can only be mined with difficulty.

The ancients obtained important copper ores from the mines of the Isle of Cyprus. The Greeks obtained silver from the silver mines of Laurium (of ancient Greek). The ancient tin mines of Cornwall were exploited by the Romans, and probably even by the Phoenicians.

The methods of mining used were of the crudest. Only the simplest of hand tools were available, and with these a single miner working in solid rock could generally not mine much more than a basket of ore per day. The labor employed in the mine was primarily that of slaves, frequently working in chain gangs. In passages too small for adults, children were employed.

Few written records of the earlier mining practices have been preserved to the present time, due largely to the fact that the writing of the time was done primarily by the philosophers and others who felt it distinctly beneath their dignity to dirty their hands with the work-a-day labor of the world sufficiently to inform themselves on such processes. This much is known, however, that the mining methods of the ancients were sufficiently thorough in the localities worked by them that little has been left to be done by more modern methods except at depths greater than the ancients were able to penetrate.

This increase in the use of metals had the social effect not only of increasing the prowess of man but also of increasing the technical problems presented by the mining methods themselves that he was called upon to solve. The ancients found their operations curtailed and finally balked at depth by the inflow of ground water into the workings of the mines. If greater depths were to be obtained suitable pumps must be devised, and since the water flowed in continuously, pumping operations had to be maintained.

This required power. The solution of the problem, together with that of hoisting ores and rock from the mines, may very well be said to have laid the foundation stones for the future mechanical development.

Various kinds of windlasses and pumps were developed; at first only the muscle power of human beings was employed, then oxen working on treadmills were used, and later in a similar manner horses were employed. Where suitable waterfalls occurred, water wheels were developed, employing the energy contained in the waterfall for pumping and hoisting. In other cases, windmills were developed employing the energy of the wind for a similar purpose. Had only these sources of energy been available, the mining and consequently the industrial development of the future would have been seriously handicapped. The crying need was for newer and larger sources of energy.


We have thus traced the high points of the development of man’s conquest of energy through its initial stages.

We have found that every new technical device—the domestication of plants and animals, the use of tools, such as the club, the boat, wheeled vehicles, and finally the use of metals—has each played its part in contributing to a diversion of an ever-increasing part of the sun’s energy into uses of the human species.

The extensive use of metals was among the most significant and far-reaching in its effect of the events in human history. It not only disturbed the biological equilibrium resulting in an increase in human population at the expense of the other species, but it also, in a similar manner, gave certain peoples an advantage, due to their greater command of energy, over other people not so favorably equipped. This resulted in a disturbance of the equilibrium within the human species in favor of those with the greater command of energy.


  • The Biology of Population Growth, Pearl.
  • Elements of Physical Biology, Lotka.
  • Man and Metals, Rickard.
  • History of Mechanical Inventions, Usher.