Imágenes de páginas
PDF
EPUB

MAN AND CIVILIZATION

Part I

THE WORLD WE LIVE IN

CHAPTER 1

THE BIOLOGICAL VIEW OF HUMAN NATURE

The continuity of life.

The first beginnings of life seem lost forever in the darkness of the past. Neither the time nor the place when it first appeared has come down to us. Did it arise from the sea an eon or two ago, under the favoring ministrations of that equitable environment, or was it spawned in the heavy airs of a distant Archeozoic age? The past returns no settled answer.

After life has once appeared, however, the history of its ramifications and development through the ages can be told with increasing precision and detail as we approach the present. The romantic story of evolution contains many plots, but the most interesting of them all is that of the unbroken web of life. All living things of whatever sort are bound by living ties to the past, first of their own kind, and then through them to yet other kinds, back-far back-to the remote beginning of things. The very fact that they are here alive is proof positive that the continuity has never been broken.

Characteristics of living things.

All present life may not go back in the end to the same precise source, for there may have been several distinct beginnings, at the same time or at different times, but the almost infinite

number of matings since that early day makes it all but certain that all living things belong to the same great family-by biological interchange, as it were, if not by direct descent. In any event, they share certain properties or traits, among which are the following:

(1) Cellular structure. Plants and animals alike are composed of highly complex organic compounds * which are collectively called protoplasm. Although protoplasm differs in its specific constitution from one species to another, and even within the same species, it combines in every instance to form cells, which are the smallest units of living matter. While many simple plants and animals are single-celled, the more complex organisms are composed of colonies or aggregations of many cells in various degrees of association. Thus it has been estimated that the thin outer coating of the human brain contains considerably over nine billion nerve cells alone, besides numerous cells of other types. The human being, like all other complex organisms, is therefore really a great interacting society of living creatures in differing degrees of dependence on each other. Even the simplest cell is itself a very intricate organism containing a variety of specialized parts in a highly unstable state of equilibrium.

(2) Metabolism. Every organism maintains itself by the intake and assimilation of materials from outside of itself, and by the accompanying excretion of waste products. The process is essentially one of oxidation, in the course of which complex substances are broken down and energy released, while at the same time the resulting materials are incorporated into the structure of the organism. The food-needs of an organism are always fairly specific, and they are also regularly recurrent. This has the effect of binding each organism rather closely to the natural environment which is capable of satisfying its needs.

(3) Reproduction. Living things are capable, upon occasion, of giving birth to other living things like themselves. The process is a complicated one even in its simplest forms, and varies greatly from species to species, but, however caused, involves cell division. In the case of human beings, the reproductive process is initiated by the fertilization of a female germ cell (or ovum) by a male germ cell (or spermatozoon) within the body of the future mother, and is completed by the birth of the new individual some nine months after fertilization.

(4) Irritability or motility. There is a continuous response and reaction to the outside energies which incessantly play upon every organism; and there is an equally continuous release of

*I.e., comounds whose basic component is carbon, in intimate association with exygen, hydrogen, and nitrogen, and to a less degree with other elements.

internal energies. This interplay, which in the end is no doubt caused by the fundamental instability of the cell, goes on without rest or ceasing, and must be regarded as constituting the organism in all of its manifestable features, whether to itself or to others. Life can best be summed up in this unintermittent process of inner and outer adjustment. When we wish to emphasize the changes within the organism itself which take place during this interaction, we refer to the irritability (or sensitivity) of the organism; when we are more interested in the external motions or actions which are involved we speak of its motility. In each instance we are concerned with essentially the same process, though from two slightly different points of view.

Birth a mere incident in the life process.

Let us now consider the fact of birth in the light of the foregoing considerations. Human beings seem to make a great deal out of being born, but from the point of view of the life process it amounts less to a beginning than to a change of scene and status. The birth of a child gives us neither the beginning of life in general, nor of that life which animates the newborn infant. This comes, through germ cells furnished by the parents, from a far distant past. Nor can birth be counted the real beginning of independent existence. The baby, the child, and perhaps even the adult as well, are continuously dependent upon things and persons outside themselves for their welfare and even their existence. Nor does the child bring with him at birth anything but the vaguest intimations of a personality or character. To start with he is hardly more than the insistent embodiment of certain needs; and what he shall be, both for good and for ill, depends more on how these needs are satisfied than on the nature of the needs themselves.

Birth not a major crisis in the life-history of individuals.

Even in terms of our own history birth can hardly be regarded as of paramount importance. It is, of course, a crisis, a time of alteration and of danger, but hardly a crisis of the first order when compared, say, with (1) the moment of fertilization, (2) the first three or four years of life, or (3) the period centering around adolescence.

(1) At the moment of fertilization, when male and female germ cells combine to initiate the processes of cell division and development which finally result in a human being, the main hereditary outlines of our equipment are laid down-in no de

tailed and arbitrary manner independently of all further experience, as we shall see, but within limits nevertheless.

(2) During the first three or four years of life, including the period of nine months in the womb and the years that follow, we come more closely and pervasively under the influence of the physical and social environment than at any succeeding period, and that too at a time when, by virtue of our weakness, immaturity, and ignorance, we are rendered exceedingly susceptible to the pressures and influences continually being laid upon us. It is during this time that broad life interests and reactions are largely determined, and most of the basic trends of later days laid down. During the long season in the even environment of the womb, the whole bodily structure is built up in all of its broad outlines, and the basis laid for many of the behavior patterns of later life.* Nor are the first years after birth less important, for it is then that most children form those drives towards mastery or submission, those curiosities, apathies, interests, and aversions, those habits of cleanliness, carefulness, and attention (or their opposites), and those countless other traits and behaviors which so often last throughout the years and mark them off as distinct from other persons until their dying day.

(3) Finally, during the period of adolescence new powers and interests centering around sex make their appearance, and these very greatly alter the terms within which life is lived. It is then that our lives seem to be taken apart and in many respects made over, though in most respects with the same elements that have served us up to the time of puberty. It is then, also, that most persons find awakening in them new emotional attitudes towards their fellows, and a new sense of obligation to the group which, however fitful and evanescent, nevertheless greatly changes life's main contours.

Our contact with the past.

Each generation is in contact with past generations in two ways of which one is biological and the other social in nature. The interdependence of these two types of connection is so important that a thorough understanding either of human nature or of social phenomena is hardly possible until it has been mastered. It will be best, however, to begin the discussion with a summary description of each type of connection considered in isolation, and then to pass on to the indication of relationships.

By a behavior pattern is meant some specific organization of response, as the thrusting out of the arms when one has stumbled, or the motions one goes through in signing one's name.

Biological contact with the past. The direct line of biological connection is through the germ cells of the parents, and is called heredity. The germ cells of each parent carry within them a large number of "determiners," and these determiners in some unknown fashion act upon the process of cell division in such a manner as to affect the course of development in specific directions. Thus the presence of the determiner (or group of determiners) for dark eyes in due course leads to the development of these eyes in the foetus, or unborn child. No description of the numerous and complicated ways in which the determiners laid away in the germ cells of the two parents combine need be offered at this juncture. It should be pointed out, however, that the determiners that fail to be of effect in any given generation seem not to be lost, but remain present in the germ plasm ready to put in an appearance, under the appropriate conditions, in some later generation. The determiners which do act to form the bodily traits are also present in the germ plasm. Likewise, it occasionally happens, for reasons that remain obscure, that new determiners (or combinations of determiners) are created, and the result is the appearance of new traits in the course of development. These new traits are called mutations.

The different ways in which the determiners of the two parents interact follow laws whose nature was first indicated by studies made on the common vegetable pea by Gregor Mendel, an Austrian monk. The science of biology was entirely revolutionized as a result of the discovery of his work in 1900, after it had lain fallow for thirty-five years in an obscure scientific periodical.1*

To the contemporary biologist, the line of hereditary descent is from germ cell to germ cell, each fertilized ovum producing new germ cells whose nature is almost completely unaffected by what happens to all the other cells in the course of their developments. To put the matter within the terms of the old query about the chicken and the egg, the egg comes first, and produces both the chicken and additional eggs, which have in turn the same property of producing yet other chickens and eggs. The chicken, as Samuel Butler was fond of pointing out, is only an egg's way of producing another egg. From the biological point of view it is often profitable to look on the body as merely the carrier of the germ plasm.

* Numerals are used in referring to bibliographical notes, which are to be found at the end of each chapter.

The discontinuity between the germ cells and the body is not absolute, since certain conditions in one or both of the parents (as alcoholism or syphilis) affect the germ plasm. In addition evidence is accumulating in favor of the inheritance of acquired characters in certain very specific instances. See also the discussion in the next section but one on the influence of group arrangements upon the biological constitution of the group for additional considerations bearing on the main point.

« AnteriorContinuar »