In the strata of the earth, either in the late second inter-glacial period or at the beginning of the third, chipped rocks, or eoliths, are found used by races of which the Piltdown and Heidelberg species are representatives.[3] Originally man used weapons to hammer and to cut already prepared by nature. Sharp-edged flints formed by the crushing of rocks in the descent of the glaciers or by upheavals of earth or by powerful torrents were picked up as needed for the purpose of cutting. Wherever a sharp edge was needed, these natural implements were useful. Gradually man learned to carry the best specimens with him. These he improved by chipping the edges, making them more serviceable, or chipping the eolith, so as to grasp it more easily. This represents the earliest relic of the beginning of civilization through art. Eoliths of this kind are found in Egypt in the hills bordering the Nile Valley, in Asia and America, as well as in southern Europe. Perhaps at the same period of development man selected stones suitable for crushing bones or for other purposes when hammering {31} was necessary. These were gradually fashioned into more serviceable hammers. In the latter part of this period, known as the pre-Chellean, flint implements were considerably improved. In the Lower Paleolithic in the pre-Neanderthal period, including what is known as the Chellean, new forms of implements are added to the earlier beginnings. Almond-shaped flint implements, followed later by long, pointed implements, indicate the future development of the stone spear, arrowhead, knife, and axe. Also smaller articles of use, such as borers, scrapers, and ploughs, appeared. The edges of all implements were rough and uneven, and the forms very imperfect. _Industrial and Social Life of Primitive Man_.--In the industry of the early Neanderthal races (Acheulean) implements were increased in number and variety, being also more perfectly formed, showing the expansive art of man. At this period man was a hunter, having temporary homes in caves and shelters, which gradually became more or less permanent, and used well-fashioned implements of stone. At the close of the third interglacial period the climate was mild and moist, and mankind found the open glades suitable places for assemblages in family groups about the open fires; apparently the cooking of food and the making of implements and clothing on a small scale were the domestic occupations at this time. Hunting was the chief occupation in procuring food. The bison, the horse, the reindeer, the bear, the beaver, the wild boar had taken the place of the rhinoceros, the sabre-tooth tiger, and the elephant. Judging from the stage of life existing at this time, and comparing this with that of the lowest living races, we may safely infer that the family associations existed at this time, even though the habitations in caves and shelters were temporary.[4]