EVOLUTION. 332 EVOLUTION. Heredity. The work accomplished by the fac- tors of evolution, including natural selection, would be all lost were the progressively developed characters not transmitted and fixed by heredity. Every one is familiar with the effects of the action of heredity. Its cause has been a mystery, now, however, in part cleared up. .See Heredity; Use-Inheritance. Parasitism. A very considerable portion of the animal world lives at the expense of its hosts. Whole orders of protozoans, worms, crus- taceans, several families of hymenopterous and dipterous insects, numerically rich in species, and members of many other classes, derive their ex- istence by simply living within the bodies of their hosts, or attaching themselves to some ex- ternal part of their bodies. They infest the blood, the muscles, glands, and, in fact, may in- vade every organ and tissue in the body. A signal example of the good done by parasitic in- sects in preventing the overcrowding of the earth with injurious insects is the ichneumon fly (q.v. ), a parasite of caterpillars, etc. The competition which is going on in the world of life is perhaps no better illustrated than by the work done by those deadly enemies of animal life of all grades, the disease germs or bacteria ; yet the bacteria are met and devoured by wandering cells, whose mission it is to prey on such germs. In short, by a study of these parasitic degen- erate forms, in many of which there is a loss of limbs and other organs, we readily understand what a potent cause of profound modification by disuse the habit of parasitism may prove to be. In human history the occurrence of individual and racial weakness, backwardness, and decay due to the various forms of parasitic existence, includ- ing slavery, is a conspicuous source of physical and moral degeneration, and is exactly paral- leled and illustrated among certain social insects. See Ant and Insect, section Social Insects. The Origin of Man. The proofs of man's origin from some other primate is now strong. Anatomically he presents no absolute differences from the anthropoid apes, except in the organs of speech. The relative differences between man and apes are very great, though chiefly confined to the capacity of the skull, the size, number, and complexity of the convolutions of the brain, and the specialization of the forearm in direc- tions ministering to the behests of his brain. He passes through the same embryological phase? as the higher mammals. Man's origin from some mammal is strongly attested by the presence in his body of a large number of vestigial charac- ters, which indicate an ancestor that went on all fours — some features appearing shortly before and after birth, hinting at an ape ancestry. The scanty remains of the fossil races, that of Neanderthal or Spy, exhibit some primitive characters, but the discovery of In. skull-cap, femur, and molar teeth of 1 ho Javan so-called 'missing link' (Pithecanthropus erectus) affords weighty evidence of the descent of man from Bome gibbon-like ape. (See Gib- bon.) Expert a in craniology state that the crani- al capacity of this intermediate form is about 1000 cubic centimeters, while that of a few Aus- tralian skulls is even less than thai (850 cubic centimeters). (See Pithecanthropus.) This creature stood erect, and was of the average height of "i. in i nless, then, new discoveries ■ I li< i tropical region, the view may be provisionally held that man arose in .lava, or at least in southeastern Asia, where members of the lowest race of mankind — the Aetas of the Philippines — still exist, and until recently the Kalang-people of Java, a race of negritos allied to the Akkas of Central Africa. At the outset man was a social being: his erect posture, large brain, hands, so well adapted t.i carrying out the suggestions of his developing intellect, so that he was the first tool-maker and worker in stone, bone, and wood, and the first being to tame other animals and to cultivate the soil — these qualities enable him to dominate all other animals. At first living a roving, soli- tary life as a hunter, tribal communities gradually arose here and there, living in fixed habitations and leading a sedentary life, and the develop- ing man eventually became a herdsman, and after long ages a farmer. Even temporary cessations from intertribal wars were provocative of intellec- tual growth, and permitted the origin and growth of the germs of the arts and sciences. Meanwhile he began to migrate, and became, during the Paleolithic age, scattered over wide areas of the earth's surface. Then ensued a process of isola- tion by geographical and climatic barriers and the differentiation into races, the black being confined to Africa, the yellow to Asia, the red Indian to the Americas, while the cradle of the white race was in the region now including cen- tral and southern Europe, and Africa north of the Sahara and the Sudan. The more civilized man grew, the more pro- lific he became. The lowest races early, as a rule, ceased to grow. The yellow races in subtropical legions advanced much further in the arts and sciences, but finally remained in a comparatively backward, semi fossil condition. Social Evolution. Up to a certain stage of de- velopment — that of the lowest savagery — the evo- lution of man was due to the action of the same transforming factors as affected lower organic life. The struggle for life, for food, for place, for preeminence, was, however, stronger in the human species than among the animals. Primi- tive man, his animal passions enhanced by his powerful emotions, stimulated by his growing imagination, his dawning intellectual forces, and his growing self-consciousness, rendered this new creature more cruel, bloodthirsty, and revengeful than the beasts. At first war did not tend to nation-building, but was a sporadic outbreak of intertribal inherited hate and revenge, with little result other than brutal sport and exercise. Mar- riage was little more than animal mating, owner- ship in property communal, and the primitive spoken language had not arisen out of signs and gestures, through picture-writing, into rude al- phabets and a written language. As soon as some scattered tribes had adopted a stationary mode of life, began to cultivate the soil, had domestic animals, and through various necessities made useful inventions, man began to live in a world of new ideas. With fixed abodes, family and tribal customs became handed down, finally becoming laws, and as the result of tribal combats patriotism and the social virtues took root. With ancestor-worship, reverence for the dead, ideas of a future life, poetry, art. archi- tecture, sprang up. Commerce was. even in I!"' earliest ages, as now, a great civilizer, as was ownership in Hocks and herds and in land. Man began to have his individual rights, and the
