And it is not without interest to notice that a fall in the temperature of the earth is the immediate cause of this social life. The building of homes of any kind seems to be unknown to Magdalenian man. The artist would have left us some sketchy representation of it if there had been anything in the nature of a tent in his surroundings. The rock-shelter and the cave are the homes which men seek from the advancing cold. As these are relatively few in number, fixed in locality, and often of large dimensions, the individualism of the earlier times is replaced by collective life. Sociologists still dispute whether the clan arose by the cohesion of families or the family arose within the clan. Such evidence as is afforded by prehistoric remains is entirely in favour of the opinion of Professor Westermarck, that the family preceded the larger group. Families of common descent would now cling together and occupy a common cavern, and, when the men gathered at night with the women for the roasting and eating of the horse or deer they had hunted, and the work of the artist and the woman was considered, the uncouth muttering and gesticulating was slowly forged into the great instrument of articulate speech. The first condition of more rapid progress was instinctively gained. Our story of life has so often turned on this periodical lowering of the climate of the earth that it is interesting to find this last and most important advance so closely associated with it that we are forced once more to regard it as the effective cause. The same may be said of another fundamental advance of the men of the later Palaeolithic age, the discovery of the art of making fire. It coincides with the oncoming of the cold, either in the Mousterian or the Magdalenian. It was more probably a chance discovery than an invention. Savages so commonly make fire by friction--rubbing sticks, drills, etc.--that one is naturally tempted to regard this as the primitive method. I doubt if this was the case. When, in Neolithic times, men commonly bury the dead, and put some of their personal property in the grave with them, the fire-kindling apparatus we find is a flint and a piece of iron pyrites. Palaeolithic man made his implements of any kind of hard and heavy stone, and it is probable that he occasionally selected iron ore for the purpose. An attempt to chip it with flint would cause sparks that might fall on inflammable material, and set it alight. Little intelligence would be needed to turn this discovery to account.