The answer is unwavering; retrogression is not in the creative plan.
"A Handbook to the Works of Browning (6th ed.)"
Mrs. Sutherland Orr
That is to say, Natural Selection is just as ready to degrade as to elevate a creature, according to the actual requirements of the circumstances in which it is placed, and how far progress has been the rule, rather than stability or retrogression, is a question for geological history to determine.
"The Old Riddle and the Newest Answer"
John Gerard
Spiritually humanity's record is one of retrogression.
"The Orchard of Tears"
Sax Rohmer