In making regulations about this partnership he should have regard both to the spouses themselves and to their length of life, in order that they may arrive at the right ages together at the same time, and so that the period of the father's ability to beget and that of the mother's to bear children may coincide. A period when one of the two is capable and the other not leads to mutual strife and quarrels. Next as regards the timin g of the children's successsion, there should not be too great a gap in age between fahter and children; for when then there is no good that the young can do by showing gratitude to elderly parents, and their fathers are no help to them. Nor should they be too close in age, for this causes the relationship to be strained: like contempories, people in such a position feel less respect, and the nearness in age leads to bickering in household affairs.
All these purposes can be fulfilled, or nearly so, if we pay sufficent attention to one thing. Since, generally speaking, the upper age limit for the begetting of children is for men seventy years and for women fifty, the beginning oftheir union should be at ages such that they will arrive at this stage of life simultaneosly. But the intercourse of a very young couple is not good for child-bearing. In all animals the ofspring of early unions are defective, inclined to produce females and diminuitive; so the same kind of results are bound to follow in human beings too.
Also young women have greater difficulty in giving birth and more of them die. It is also more conducive to restraint that daughters should be no longer young when their fathers bestow them in marriage, bacause it seems that women who have sɛҳuąƖ intercourse at an early age are more likely to be dissolute.
Accordingly we conclude that the appropriate age for the union is about the eighteenth year for girls and for men thethirty-seventh, with such timing, their union will take place when they are physically in their prime, and it will bring them down together at the end of procreation at exactly the right moment for both. And the childrens succesion, if births take place promptly at the expected time, will occur when they are at the beginning of their prime and their parents past their peak, the Father now approaching his seventieth year.