The meaning of long lives mentioned in certain ancient books and narratives

At the morning gathering of the friends one asked about the longevity of life in ancient times. The Master replied:

Some think that is a third motion of the earth which is the cause of the length or shortness of life. This motion, they say, is different from the diurnal and annual motions and is the cause of change in the condition of the globe. But the long lives mentioned in certain books and narratives have a different basis. For instance, it was a custom in former times to mention a dynasty or family by the name of one person only. However, the people in the following ages thought that the length of time that a family survived was the length of the life of that family’s founder.