 Why does Sias believe that the ancients declared 70 as the minimum age for a member of the Conclave?
They are of an age to enter manhood, and have all the energy such young men do. They were created so long ago, indeed, that the ignorant believe them to have been constructed by the gods themselves. Indeed, the watcher is more a tradition than a necessity. Prayers and supplications were offered to the gods, priests were sent to sacrifice, and finally, as the light of the sun was falling between the pillars, the High Priest of the Maternite Machine was heard. By this time, unfortunately, many of the Conclave had departed for home and supper. The machines bear the exact number of children each year to balance the number of us whom the gods claim.
 They do not have the energy to riot amongst themselves
 They are the ones who remember things from previous generations that get lost to time  They do not have the energy to riot amongst themselves  They are closest in lineage to the predecessors that generated the machines  They have had sufficient life experience at that point