The origin of the Celts is more certain. Unlike the Iberians they were of Indo-European race. In the third century B.C. they occupied a territory embracing the greater part of the lands from the modern Balkan states through northern Italy and France, with extremities in Britain and Spain. They entered the peninsula possibly as early as the sixth century B.C., but certainly not later than the fourth, coming by way of the Pyrenees. It is generally held that they dominated the northwest and west, the regions of modern Galicia and Portugal, leaving the Pyrenees, eastern Spain, and part of the south in full possession of the Iberians. In the centre and along the northern and southern coasts the two races mingled to form the Celtiberians, in which the Iberian element was the more important. These names were not maintained very strictly; rather, the ancient writers were wont to employ group names of smaller sub-divisions for these peoples, such as Cantabrians, Turdetanians, and Lusitanians. [Sidenote: Celtiberian civilization.] It is not yet possible to distinguish clearly between Iberian and Celtic civilization; in any event it must be remembered that primitive civilizations resemble one another very greatly in their essentials. There was certainly no united Iberian or Celtic nation within historic times; rather, these peoples lived in small groups which were independent and which rarely communicated with one another except for the commerce and wars of neighboring tribes. For purposes of war tribal bodies federated to form a larger union and the names of these confederations are those which appear most frequently in contemporary literature. The Lusitanians, for example, were a federation of thirty tribes, and the Galicians of forty. The social and political organization of these peoples was so similar to others in their stage of culture, the world over, that it need only be indicated briefly. The unit was the gens, made up of a number of families, forming an independent whole and bound together through having the same gods and the same religious practices and by a real or feigned blood relationship. Various gentes united to form a larger unit, the tribe, which was bound by the same ties of religion and blood, although they were less clearly defined. Tribes in turn united, though only temporarily and for military purposes, and the great confederations were the result. In each unit from gens to confederation there was a chief, or monarch, and deliberative assemblies, sometimes aristocratic, and sometimes elective. The institutions of slavery, serfdom, and personal property existed. Nevertheless, in some tribes property was owned in common, and there is reason to believe that this practice was quite extensive. In some respects the tribes varied considerably as regards the stage of culture to which they had attained. Those of the fertile Andalusian country were not only far advanced in agriculture, industry,