Allan Kardec. The book of spirits (№ 397021)

Question: the Spirit, that once in the period of mankind that does more traces than he was before, the traces of the state during a period which can be called pre-human period?
Answer: It depends on the time potekshego between the two periods, and the progress of the perfect spirit. In the first few incarnations of it may remain more or less clear reflection of the primitive of its existence, because in nature there are no abrupt transitions; there are always links that support continuity as the chain of beings and events, but these traces fade as the development of free will. Initially the progress is slow, because it is not supported yet will; as well as the spirit gains more consciousness, the progress is faster.