I had two inspirations to this illustration. One was the Rudolph Zallinger's illustration "The March of Progress", also known as "Road to Homo sapiens", originally published of a section of text and images commissioned by Time-Life Books for the Early Man volume (1965) of the Life Nature Library, by F. Clark Howell Other inspiration was "The Sixth Finger", an episode from "The Outer Limits" tv science-fction anthology series.