He never used stone for building house walls until upon the very verge of history. He used stone for hearths (_e.g._ at Glastonbury) and sometimes stone sub-structures. He did, however, make a sort of stone house in the centre of the great mounds in which he buried his illustrious dead. He may have learnt this custom from his Iberian neighbours and predecessors. It was these dark whites of the heliolithic culture, and not the primitive Aryans, who were responsible for such primitive temples as Stonehenge or Carnac in Brittany. His social life was growing. Man was now living in clans and tribal communities. These clans and communities clashed; they took each other’s grazing land, they sought to rob each other; there began a new thing in human life, _war_. For war is not a primeval thing; it has not been in this world for more than 20,000 years. To this day very primitive peoples, such as the Australian black-fellows, do not understand war. The Palæolithic Age was an age of fights and murder, no doubt, but not of the organized collective fighting of numbers of men.[91] But now men could talk together and group themselves under leaders, and they found a need of centres where they could come together with their cattle in time of raids and danger. They began to make camps with walls of earth and palisades, many of which are still to be traced in the history-worn contours of the European scenery. The leaders under whom men fought in war were often the same men as the sacrificial purifiers who were their early priests. The knowledge of bronze spread late in Europe. Neolithic man had been making his slow advances age by age for 7000 or 8000 years before the metals came. By that time his social life had developed so that there were men of various occupations and men and women of different ranks in the community. There were men who worked wood and leather, potters and carvers. The women span and wove and embroidered. There were chiefs and families that were distinguished as leaderly and noble; and man varied the monotony of his herding and wandering, he consecrated undertakings and celebrated triumphs, held funeral assemblies, and distinguished the traditional seasons of the year, by _feasts_. His meats we have already glanced at; but somewhen between 10,000 B.C. and the broadening separation of the Aryan peoples towards 2000 or 1000 B.C., mankind discovered fermentation, and began to brew intoxicating drinks. He made these of honey, of barley, and, as the Aryan tribes spread southward, of the grape. And he got merry and drunken. Whether he first used yeast to make his bread light or to ferment his drink we do not know.