+88. Variability.+ No less remarkable than the persistency of the mores is their changeableness and variation. There is here an interesting parallel to heredity and variation in the organic world, even though the parallel has no significance. Variation in the mores is due to the fact that children do not perpetuate the mores just as they received them. The father dies, and the son whom he has educated, even if he continues the ritual and repeats the formulae, does not think and feel the same ideas and sentiments as his father. The observance of Sunday; the mode of treating parents, children, servants, and wives or husbands; holidays; amusements; arts of luxury; marriage and divorce; wine drinking,--are matters in regard to which it is easy to note changes in the mores from generation to generation, in our own times. Even in Asia, when a long period of time is taken into account, changes in the mores are perceptible. The mores change because conditions and interests change. It is found that dogmas and maxims which have been current do not verify; that established taboos are useless or mischievous restraints; that usages which are suitable for a village or a colony are not suitable for a great city or state; that many things are fitting when the community is rich which were not so when it was poor; that new inventions have made new ways of living more economical and healthful. It is necessary to prosperity that the mores should have a due degree of firmness, but also that they should be sufficiently elastic and flexible to conform to changes in interests and life conditions. A herding or an agricultural people, if it moves into a new country, rich in game, may revert to a hunting life. The Tunguses and Yakuts did so as they moved northwards.[105] In the early days of the settlement of North America many whites "Indianized"; they took to the mode of life of Indians. The Iranians separated from the Indians of Hindostan and became agriculturists. They adopted a new religion and new mores. Men who were afraid of powerful enemies have taken to living in trees, lake dwellings, caves, and joint houses. Mediaeval serfdom was due to the need of force to keep the peasant on his holding, when the holding was really a burden to him in view of the dues which he must pay. He would have run away if he had not been kept by force. In the later Middle Ages the villain had a valuable right and property in his holding. Then he wanted security of tenure so that he could not be driven away from it. In the early period it was the duty of the lord to kill the game and protect the peasant's crops. In the later period it became the monopoly right of the lord to kill game. Thus the life conditions vary. The economic conjuncture varies. The competition of life varies. The interests vary with them. The mores all conform, unless they have been fixed by dogma with mystic sanctions so that they are ritual obligations, as is, in general, the case now in southeastern Asia.