Moreover, man as a social being early began to learn that he could claim something from his fellows, and that he owed something to them. If he refused to help others, they would refuse to help him. This was his first, very rude lesson in rights and duties. Love, duty, and right have ever since been the watchwords of his development and progress. We have not yet considered, and must for the present disregard, the value and efficiency of religion in aiding his advance. At present we emphasize only the historical fact that man has not become what he is by a higher development of the body, nor by giving free rein to appetite, nor yet by making the dictates of selfish prudence supreme. And if there is any such thing as continuity in history, such modes and aims of life, if now followed, would surely only brutalize him and plunge him headlong in degeneration. He must live for right, truth, love, and duty. In just so far as he makes any other aim in life supreme, or allows it to even rival these, he is sinking into brutality. This is the clear, unmistakable verdict of history, and we shall do well to heed it.
But granting all that can be claimed for this sequence, have not the lower forms whose anatomy we have sketched--worm, fish, and bird--halted at various points along this line of march? Yet they have evidently survived. And if they have found safe resting-places, cannot higher forms turn back and join them? In other words, is not degeneration easier than advance and just as safe? What is the result if an animal tries to return to a lower plane of life or refuses to take the next upward step? Generally extermination. The very classification of worms in a number of small isolated groups, which must once have been connected by a host of intermediate forms, is indisputable proof of most terrible extermination. They did not go forward, and the survivors are but an infinitesimal fraction of those which perished. Let us take an illustration where palæontology can help us. The earth was at one time covered with marsupial mammals. Some advanced into placental forms. The great mass remained behind. And outside of Australia the opossums are the only survivors of them all. And this is only one example where a thousand could be given. Place is not long reserved for mere cumberers of the ground. There are so few exceptions to this statement that we might almost call it a law of biology.