The Spirits' Book
Book Three - Moral Laws
Chapter IV - III. Law of Reproduction
Succession and Development of the Human Race
691. From a physical standpoint, what are the unique and dominant characteristics of prehistoric races?
“They are characterized by the development of physical power to the detriment of intellectual power. Right now the opposite occurs, human beings act through their intelligence rather than through their bodily strength and accomplish a hundredfold more than they did in the past because they have learned to leverage the forces of nature, which animals cannot do.”