Reincarnation being the great law of life and progress, it is interwoven with that of the cycles and karma. These three work together, and in practice it is almost impossible to disentangle reincarnation from cyclic law. Individuals and nations in definite streams return in regularly recurring periods to the earth, and thus bring back to the globe the arts, the civilization, the very persons who once were on it at work. And as the units in nation and race are connected together by invisible strong threads, large bodies of such units moving slowly but surely all together, reunite at different times and emerge again and again together into new races and new civilizations as the cycles roll their appointed rounds. Therefore the souls who made the most ancient civilizations will come back and bring the old civilization with them in idea and essence, which being added to what others have done for the development of the human race in its character and knowledge, will produce a new and higher state of civilization.
Universal Brotherhood PathTHEOSOPHICAL UNIVERSITY PRESS ONLINE