What is the purpose of man’s repeated appearance on Earth? If there were no connection between the various incarnations, the whole process would of course be senseless, but that is not how it goes. Think how different life was for a man who was incarnated a few centuries after Christ, compared with the conditions he will find when he reincarnates today. Nowadays a child’s life between the sixth and fourteenth years is taken up with acquiring knowledge: reading, writing, and so on. Opportunities for the cultivation and development of human personality are very different from what they were in the past.
A man’s incarnations are ordered in such a way that he returns to the Earth only when he will find quite new conditions and possibilities of development, and after a few centuries they will always be there. Think how quickly the Earth is developing in every respect: only a few thousand years ago this region was covered with primeval forests, full of wild beasts. Men lived in caves, wore animal skins and had only the most primitive knowledge of how to light a fire or make tools. How different it all is today! We can see how the face of the Earth has been transformed in a relatively short time. A man who lived in the days of the ancient Germanic people had a picture of the world quite different from the picture which prevails today among people who learn to read and write. As the Earth changes, man learns quite new things and makes them his own.
Source: Rudolf Steiner – GA 95 – At the Gates of Spiritual Science – Lecture IV: Devachan – Stuttgart, 25th August 1906