You need no proof that methods of transportation have undergone a continuous process of evolution. So marked has the change been that the old one-lung type of automobile now provokes a laugh wherever it is found on the street.
The law of evolution is always and everywhere at work, changing, tearing down and rebuilding every material element on this earth and throughout the universe. Towns, cities and communities and undergoing constant change. Go back to the place where you lived twenty years ago and you will recognize neither the place nor the people. New faces will have made their appearance. The old faces will have changed. New buildings will have taken the place of the old. Everything will appear differently because everything will be different.
The human mind is also undergoing constant change. If this were not true we would never grow beyond the child-mind age. Every seven years the mind of a normal person becomes noticeably developed and expanded. It is during these periodical changes of the mind that bad habits may be left off and better habits cultivated. Fortunate for the human being that his mind is undergoing a continuous process of orderly change.
~ Napoleon Hill, The Law of Success (1928)