Love: A Treatise on the Science of Sex-attraction / for the use of Physicians and Students of Medical Jurisprudence

PART II.
EVOLUTION OF SEX

CHAPTER I
ORGANIC EVOLUTION

The emotion of love, like any other psychic trait, is subject to the laws of evolution. Its history is written on the pages of Life’s book. The amatory emotions have followed step by step the evolution of plant and animal.

The fact of organic evolution is nowadays tacitly accepted even by those powers who in a not very remote period fought against the theory of the heliocentric system. What is still sub judice is the method of evolution. Here we have two main theories:

1. The mechanistic.

(a) Neo-Lamarckians.
(b) Neo-Darwinians.

2. The vitalistic.

(a) Teleology.
(b) Creative evolution.

According to the mechanistic theory, all life can be accounted for through the application of the laws of physics and chemistry, while the claim of the vitalistic theory is that physics and chemistry do not explain all. Teleology holds that life is carrying out a prearranged plan; creative evolution postulates a blind primordial energy, a psychic force, a life impetus, without any prearranged plans. The Neo-Lamarckians hold that acquired characteristics during the lifetime of the individual are transmitted to its offspring. This transmission is the method of evolution. The Neo-Darwinians deny the transmission of acquired characteristics and claim that evolution has been and is effected by natural selection. The animal’s germ-cells being a product of its own soma-cells and the parents’ germ-cells, they must change continually, since the soma-cells are being continually changed. Those germ-cells which are beneficial to the organism are selected by nature for preservation. The claim of the Lamarckians is that environment gives rise to variation, while the Darwinians maintain that a given variation is selected by environment for survival.

All four theories assume evolution as a fact. That the neck of the giraffe, for example, has been evolved to reach the leaves of high trees is admitted by all of them; they only differ in the principle underlying this evolution. According to teleology, the faculty to evolve a long neck has been infused into the protoplasm by the creative power, according to a prearranged plan. Creative evolution assumes a blind primordial vital impetus without purpose, end or aim. Organic life is an infinite addition, a continuance without conclusion. Creation, once started, the long neck has evolved without any previously arranged plan. The Neo-Lamarckian explains the evolvement of the long neck by the continual stretching of the organ to reach the leaves of high trees. The increase in length was then transmitted from generation to generation, each generation contributing its quota. In this way the present long neck has been evolved. The Neo-Darwinian assumes an accidental variation. At one time in the animal’s history an animal with a long neck has been accidentally bred. This variation with its higher survival value survived during a scarcity of food, while the low-necked varieties disappeared.

Neither of the four theories gives entire satisfaction to the fastidious critic. The mechanistic theory denies or rather ignores the presence of an intelligence in the universe, and the human mind, as now constituted, can not understand how the power, that could create a substance with the potentiality to develop into the human intellect, could itself be devoid of intellect. If, on the other hand, the creative power is endowed with intelligence, then its working without aim or purpose is equally unthinkable. The vitalistic theory offers other difficulties. Teleology, for instance, does not answer the question why an intelligence, unlimited by space and time, omnipotent and omniscient, should need the vast machinery of evolution to accomplish its end; why could it not create a full-fledged Adam of the theologist? Moreover, the human mind can not grasp the How, Whence and the Where of the Supreme Intelligence, except by faith, and science has no dealing with faith. The same objection may be raised against creative evolution, whence this initial, vital impetus, whence this original life?

The part of the mechanistic theory enunciated by the Neo-Lamarckians seems quite probable. Nature, or environment, does sometimes change organic beings either by chemical or by physical influences, and these changes are not seldom transmitted to the offspring. Antonio Marro (First Eugenic Congress) cites a case where a bull while leaving the stable had its tail cut off, the door suddenly closing; all the calves born through the impregnation of this bull were tailless. Marro also made guinea-pigs epileptic by the resection of the sciatic nerve, and the offspring of the animals were also epileptic. Climate, temperature, moisture, nutrition and unusual activity produce effects upon the organism, and the offspring of the new generation have in their blood and brain the consequences of the habits of their ancestors. Prolonged disuse of an organ causes its degeneration and often its disappearance. High temperature changes the color of insects which is then inheritable or racial. Poisons such as alcohol, syphilis, arthritic diathesis, intoxicants of contagious diseases do also change the germ-plasma. Franz Boas (“The Immigration Commission. Changes in bodily form of descendants of Immigrants”) has found that none of the characteristics of the human types that come to America remain stable. Not even those characteristics of a race which have proved to be most permanent in their old home, as the form of the head, remain the same under the new surroundings. The length of the head of the brachycephalic Hebrews is increased, the width of the head and of the face is decreased. On the other hand, the length of the head of the dolichocephalic Sicilians is decreased, while the width of the head is increased. The effect of these changes is the development of a greater similarity of the descendants of Sicilians and Hebrews, one to the other. The height of body of the American-born Hebrew is increased. This influence of American environment upon the descendants of immigrants shows that acquired characteristics are transmissible. On the other hand, many facts tend to show that acquired characteristics, as a rule, are not transmitted to the offspring. Since the beginning of history circumcision has been practised among the Jews, still the Jewish boy is born with an intact prepuce.

For the reason that in the majority of cases acquired characters are not transmissible, the Darwinian rejects the explanation of evolution by appetency, or the use and disuse of certain organs, and assumes a quasi “deus ex machina” in the form of variation.

Ordinary variation is a fact that can not be disputed. No two plants or animals are exactly alike. The amphimixis or the blending of the inheritances of two individuals is, according to Weismann, the great factor in the production of variations. The two parents of every animal or plant have the species-character in common, but there are certain distinctive traits that hybridize. Hence ordinary variation is a fact, and Nature by selection may evolve, in a slow way, new species, just as Luther Burbank creates new kinds by artificial selection. Favorable variations are then bound to furnish the possessor with a greater power of resistance and with higher possibilities of life and propagation. Evolution, accordingly, occurs primarily through sudden mutations or sports which are the fittest for survival.

While the principle upon which the Lamarckian doctrines rest is the power of adaptation, the basis of evolution for the Darwinian is the transmissibility of unlikeness or individuality just as likeness. Acquired characters are not transmitted; each generation has to make a fresh start. It does not begin where the last generation has left off. But variations are transmitted to the offspring, and evolution proceeds by sports or by the transilient variation.

A serious objection to this theory is the tendency of Nature to revert to the normal average of the race. The law of Galton means the return to the mean of the species. The children of the sport tend to return towards the mean of the race.

Thus the four explanations do not satisfactorily explain, and the subject of the method of evolution is not yet decided. Neither teleology with the initiatory psychic energy working towards definite ends, nor Bergson’s vital impulse or original profound cosmic force, nor Lamarck’s appetency or use and disuse, nor Darwin’s natural selection, furnish an unobjectionable satisfactory explanation of organic evolution. Still the world’s thinkers and scientists have accepted organic evolution as a fact which may be proven by embryonic development, in conformity with Haeckel’s biogenetic axiom that ontogeny is only a short recapitulation of phylogeny.

The ovum or even the zygote (i. e., the impregnated ovum) is a single-celled organism and resembles the animals of the first or lowest type in the animal kingdom. The protozoa are nothing else than single-celled animals. Some of them have even a lower structure than the common cell. The Monera, e. g., has neither nucleus nor membrane. The manifestations of life are recognizable only by the possession of the faculties of the assimilation of food and of propagation by segmentation and division.

Like the protozoon, the ovum, immediately after its impregnation, begins to undergo a certain division, by a series of successive segmentations, into 2, then 4, 8, 16, 32, 64, etc., cells. By continuous cell segmentations a great mass, the morula or mulberry, is produced. The structure of the morula corresponds with that of the coelenterata, or the animals of the second type. To this type belong the animals with gemmiparous reproduction, or multiplication by means of buds. The divided animals remain together and form colonies, as e. g. in sponges or corals.

The next event in the formation of the embryo is the blastula. The solid spherical mass of cells becomes hollow like a rubber ball. In the subsequent stage the blastula becomes flat at one pole. By degrees a depression is formed at this point, which becomes deeper step by step, until the inner layer reaches the outer layer, representing half a sphere of two layers, like a collapsed rubber ball. In the farther growth the edges approach the middle line till they finally meet and fuse together. The oval body, called the gastrula, thus consists of two layers, the primitive germinal membranes, the ectoderm and entoderm. The gastrula resembles in its structure that of the worms, or the third type of the animal kingdom.

By certain foldings of the ento- and ectoderm transformations arise, and new organs develop. Two folds of the entoderm grow higher, approach each other and finally meet. In this way the embryo consists of four germinal membranes. A certain folding of the ectoderm marks the position of the future backbone in the primitive stripe. A longitudinal furrow marks the origin of the nerve-tube. The different membranes have thus formed several tubes, the chorda dorsalis, the definitive intestinal canal and the abdominal cavity or coelom. The structure of the embryo resembles now more or less that of the animals of the fourth type or the echinodermata.

The membranes which include the intestinal canal soon overgrow on both sides the nerve-tube and the chorda and are then differentiated partly into the bones of the skeleton and partly into the muscles. In the meantime, the vascular spaces develop. At one point of the vascular tube a rhythmical pulsation is observed, representing the primitive heart, similar to that of the mollusca.

A certain fold, the head-fold, arises at the front end of the embryo by the bending of the spinal column. Beneath the head-fold arise five processes or gills, as in fishes, which later on are transformed into the face of the fetus. Four other processes are budded off from the trunk and subsequently become the extremities. A furrow at the ventral side of the embryo shows the origin of later trachea and lungs. On both sides of the head-fold can be seen two pits for the eyes. At this point, the embryo is in the same stage of development as many arthropoda.

The skeleton begins now to ossify. The heart tube begins to bend and takes the form of an “S.” In this way the tube is turned into an auricle and ventricle as in the amphibia. The ventricle is then divided by a partition as in the reptiles. One part of the nerve-tube is differentiated into three cerebral vesicles, as in birds.

Thus the embryo resembles in its structure at different stages the structure of the different types of the animals of the animal kingdom. The different formations do not follow the chronological order as described, but, as a rule, they take place synchronously. At the end of the fourth month the fetus is about sixteen centimeters or six inches long and has reached its definite human shape.