Naturally, fossils of land animals are few compared with those of marine animals. Practically all the remains of the latter sank and were covered with the slowly accumulating sediment, while the bones of the former only rarely were swept out to sea and lake. Rarest of all fossils are those of man. A few have been found antedating history by several thousand years, but we get a far more complete knowledge of our primitive ancestors from the tools and weapons that they left in sediment and drift before the dawn of the present era. We can trace his progress upward through all degrees of culture from the rude old stone age of a hundred thousand years ago, through the new stone age, the copper and bronze age, and the iron age to the beginning of written records. Yet, so old is our planet and so long ago since life dawned on it--so long even since the first mammals appeared--that man’s arrival a hundred-or-so thousand years ago is but as yesterday. To paraphrase an illustration by Slade and Ferguson: “Suppose we take the earth as 365 million years old, and consider this period as a year, one million years being taken as a day.” Then, on this scale the vertebrates came into existence late in the summer or early fall, the mammals not earlier than the end of November, and “the whole period of man is not likely to have been further back than the evening of December 31st, and the earliest historic evidence (in Egypt) is not more than ten minutes before the last midnight.”--“the last midnight,” of course, being the present. EVIDENCES OF EVOLUTION Of the many evidences of the kinship of all animals including man only a few can be mentioned in this book. All animals, man included, are constructed on the same general plan. They have the same organs--brain, heart, lungs, digestive tract, nerves, skin--performing the same functions for the same purposes. The skeleton of man can be compared, bone for bone, with that of a monkey, bat or seal. The bat’s membranous wing is ribbed with bones corresponding to the bones of a monkey’s or a man’s hand. The wing of both the bat and the bird has one bone from the shoulder to the first joint, and two bones from the first to the second joint, like the fore leg of quadrupeds and the arm of man--thus proving that the fore leg, the arm and the wing are only modifications of the same limb. The biped bird and biped man are modified quadrupeds.