It was the economic conditions of early pastoral and agricultural communities that brought the family to its fullest fruition. Slave labour was, for most people, unavailable, and therefore the easiest way to acquire labourers was to breed them. In order to make sure that they should work for their father, it was necessary that the institution of the family should be sanctified by the whole weight of religion and morals. Gradually primogeniture extended family unity to collateral branches, and enhanced the power of the head of the family. Kingship and aristocracy depend essentially upon this order of ideas, and even divinity, since Zeus was the father of gods and men.
Source: Bertrand Russell :Marriage and Morals, 1929
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