In the construction of articles for use and ornament, copper and gold constituted the chief materials, and there was also a great deal of pottery. The art of weaving was practised, and the soil cultivated to a considerable extent. The family life was well developed, though polygamy appears to have been practised as a universal custom. The form of government was the developed family of the patriarchal type, and, where union of tribes had taken place, an absolute monarchy prevailed. War and conquest here, as in all other places where contact of tribes appeared, led to slavery. The higher classes had a large number of slaves, probably taken as prisoners of war. This indicates a degree of social progress in which enemies were preserved for slavery rather than exterminated in war. Their laws and regulations indicate a high sense of {194} justice in establishing the relationship of individuals within the tribe or nation. These people were still in the later Neolithic Age, but with signs of departure from this degree of civilization in the larger use of the metals. There were some indications that bronze might have been used in making ornaments. Perhaps they should be classified in the later Neolithic Age of the upper status of barbarism. Recent excavations in Central America, Yucatan, and more recently in the valley near Mexico City, have brought to light many new discoveries. Representations of early and later cultures show a gradual progress in the use of the arts, some of the oldest of which show a great resemblance to the early Mongolian culture of Asia.