_Battlefields and Village Sites_ (5).--In the later Neolithic period of man the tribes had been fully developed over a great part of the earth's surface, and fought for their existence, principally over territories having a food supply. Other reasons for tribal conflict, such as real or imagined race differences and the ambition for race survival, caused constant warfare. { 78} Upon these battlefields were left the implements of war. Those of stone, and, it may be said secondarily, of iron and bronze, were preserved. It is not uncommon now in almost any part of the United States where the rains fall upon a ploughed field over which a battle had been fought, to find exposed a large number of arrow-heads and stone axes, all other perishable implements having long since decayed. Or in some instances the wind blowing the sand exposes the implements which were long ago deposited during a battle. Also, wherever the Indian villages were located for a period of years, the accumulations of utensils and implements occurred which were buried by the action of wind or water. This represents a source of evidence of man's early life.
_Lake Dwellings_ (6).--The idea of protection is evidenced everywhere in the history of primitive man; protection against the physical elements, protection against wild beasts and wilder men. We find along the lakes and bays in both Europe and America the tendency to build the dwelling out in the water and approach it from the land with a narrow walk which could be taken up when not used, or to approach it by means of a rude boat. In this way the dwellers could defend themselves against the onslaughts of tribal enemies. These dwellings have been most numerous along the Swiss lakes, although some are found in Scotland, in the northern coast of South America, and elsewhere. Their importance rests in the fact that, like the shell mounds (Kitchenmiddens), the refuse from these cabins shows large deposits of the implements and utensils that were in use during the period of tribal residence. Here we find not only stone implements, running from the crude form of the Unpolished Stone Age to the highly polished, but also records of implements of bronze and small implements for domestic use of bone and polished stone. Also there are evidences that different tribes or specialized races occupied these dwellings at different times, because of the variation of civilization implied by the implements in use. The British Museum has a very large classified collection of { 79} the implements procured from lake dwellings of Switzerland. Other museums also have large collections. A part of them run back into the prehistoric period of man and part extend even down to the historic.