Essays of a Biologist

by Julian Huxley

Man has to deal with three great categories of phenomena—the inorganic, the organic, and the psychic. In the inorganic, chemistry first and then physics have given us a picture whose broad outlines are now familiar. There is but one type and store of energy in Nature, whether it drives a train, animates a man, radiates in heat or light, inheres in a falling stone. There is but one substance. All bodies of trees, of men, rivers and rocks, the clouds in the air and the air itself, precious stones and common clay—all can be resolved into a limited number of elements. And these elements in their turn can be resolved into combinations, differing, it appears, only quantitatively from each other, of electrical charges; so that at the last all matter is one, and becomes perhaps indistinguishable, or at least inseparable, from energy. There is no personal operator for particular happenings; the lightning and the volcano are the inevitable outcome of the material constitution of things, equally with the form and colour of a pebble and with the fact that it will drop to the ground if it is let fall. All is impersonal order and unity.

There is, however, one other great fact about the system of inorganic matter. The energy contained in it tends to be degraded, as the physicists say—in other words to become less readily available. There is available energy in moving matter. There is potential energy in all matter, dependent upon whether it can be set in motion. But if the sea were to cover the whole surface of the globe, it would be impossible to extract energy from running water as we do now, because no water would be running. So too heat is energy; but it is only available when it can flow, when there are hotter and colder bodies. The law under which transformations of energy operate has now been investigated, and it has been established that in every energy-transaction a certain modicum goes to waste as unavailable heat, so that, unless some at present unforeseen change occurs, the last state of the universe, considered as a purely physico-chemical mechanism, will be one of death, of inactivity, with all matter at a uniform low temperature and the whole stock of energy locked up and unavailable in this sea of tranquillity. True for one thing that an almost inconceivable number of millions of years must elapse before this “death of matter” is realized; and for another that we are unable to understand how such a progressive degradation could have been in operation from all eternity. We must not expect complete knowledge within a few years or a few centuries; but even if the beginning is veiled—for there is no more evidence for a “creation” than for (say) a rhythmic reversal of the direction of energy-availability—and if it is always possible that some unforeseen change in the process should occur before the whole runs down, yet it is a fact (and we are resolved to be agnostic save about facts) that, here and now, a direction is to be observed in the evolution of inorganic matter, by which natural operations are tending to become less active, and the amount of available energy is diminishing. If it continues indefinitely, first life, and later on all activity and change whatsoever will cease. There is a tendency towards death and towards unchanging inactivity.

The next great category is that of the organic, of living matter. We have to consider its origin and later history. So far as constitution goes, living matter is merely a special and highly complicated form of ordinary matter; and there can be no reasonable doubt that it has originated naturally from non-living matter.

While the main direction of the inorganic has been towards degradation of energy, it has shown another subsidiary direction towards the production of more and more complex forms of matter. If our general ideas are correct, there must have been a time when matter in our ordinary sense of the word did not exist—there can have been no atoms, only free electrons. From this state, there evolved one in which the various electron-systems that we call atoms first appeared; later still, atoms could join with atoms to produce molecules. Leaping over vast periods, we would come to the time when radiation had brought the temperature of the earth surface below 100 degrees centigrade; water then could form from steam and solution occur. Through solution, all soluble elements, which would otherwise remain locked in the inactivity of the solid state, are enabled to enter upon a new phase of mobility, of chemical life, as we may say. Only in water could colloid carbon compounds first be built up, and only from such substances could life originate.

Living substance, or at least much of it, must be formed of molecules containing thousands of atoms, each atom in its turn a system of circling electrons. Here already is a vast increase of complexity: it remains to be seen whether the same tendency is perpetuated later.

The evolutionary concept is to biology what the doctrine of the conservation of energy has been in the physico-chemical sciences—an indispensable preliminary to proper methods of attack. But while great stress has been laid on the various methods by which evolution may be supposed to have taken place—natural selection, Lamarckism, orthogenesis and the rest—biology has concerned herself comparatively little with the form of the process in itself. But it is here that evolution becomes of value to us in our present search; for once more we become aware of a direction. Partly from the direct evidence of palaeontology, partly from indirect evidence, but along many converging lines, we can form an idea of this direction which in broad outlines is unassailable.

During life’s existence on earth—a period to be reckoned in hundreds and probably in thousands of millions of years—there has been an increase in various of its attributes. But just as in the inorganic world electrons and atoms still exist as such side by side with molecules, so also the earlier types of living matter continue to exist side by side with the later. The increase is not therefore seen uniformly in all forms at once, but is most easily observed by studying the maximum level attained. Size, for instance, is one of these attributes; and whereas to-day all variations are to be found between ultra-microscopic disease-germs and vast organisms like whales and elephants, there has been a gradual steadying increase (tending to a limit) in the size of the largest organisms existing at any one period.

If we confine ourselves for the moment to the material side, we find that the directional change in organic evolution can be reduced to this—to an increase of the control exercised by living matter over the environment, and of its independence of the environment—two reciprocal aspects of a single process. When we look more closely into the means by which this has been achieved, we shall see an increase of the maximum not only in size, but in complexity, in length of life, in efficiency of particular organs, in co-ordination of parts and general harmony, in improvement of sense-organs, and, continuing even after other tendencies have reached their limits, in brain-size and consequently in complexity of mode of reaction and behaviour.

If we turn to the psychological side, we find that there has been an increase in the intensity of mental process. This is apparent in all aspects of mind, on that of emotion equally with that of knowledge, of volition equally with that of emotion. To be an amoeba or a worm is to live a life almost without windows. Perfection of sense-organs makes it possible for life to be aware of the different types of outer events, whilst memory and, later, associative memory give the possibility of understanding their history. In higher forms volition can be maintained for longer and longer intervals, can attain greater intensity, and can fix itself upon ever more and more distant objects. With depth of feeling comes also differentiation, so that finally we find in ourselves the possibility of organizing various blends of the simple emotions into the compound emotional forms such as reverence and admiration, called sentiments by McDougall.

Biologically speaking, therefore, the direction observable in mental evolution is again towards increased control and increased independence; by mental and cerebral improvement there is introduced a greater accuracy and a greater range of control, as well as better adjustment between organisms and environment, than would be otherwise possible to the same bodily organs.