Two Eames biographers provide insights into the history of this design.
From page 36 of AN EAMES PRIMER
by Eames Demetrios: "By 1939, Charles Eames was 32 years old and head of the design deparment at the Cranbrook Academy of Art, located just outside of Detroit. He had been there for a year os so, having practiced architecture in St. Louis for most of the decade. He had become good friends with Eero Saarinen, who was a junior partner in the architecture office of his father, Eliel Saarinen. Charles also worked on projects in the Saarinen office from time to time. At that time, Eliel Saarinen, who was also the head of the Cranbrook Academy of Art, was designing the Kleinhans Music Hall in Buffalo, NY. Saarinen Sr. was the architect of the building, and Charles and Eero designed the seating." Continuing on page 89: "So, on the Kleinhands furniture, Charles and Eero were not just collaborators, but co-conspirators exploring the curved form on a smaller scale and perhaps beginning to get a handle on the potential of molding plywood. Alvar Aalto, the great Finnish designer and master of molded plywood, had spoken at Cranbrook in the late 30s and so the whole community was aware of the material and his work forming it into simple curves. Whether the idea of the single-shell chair had formulated itself before the Kleinhans project is unclear. It is clear, however, that it is partially expressed in the Kleinhans chair." Referring back to page 36 again from this same book
, "They (EAMES & SAARINEN) determined the single striking curve for the seat by doing some research, using an array of dowels to trace the shape of the human bottom and find the curve for the most comfortable support. Although these chairs were not mass-produced for the consumer market, one can see the possibility inherent in this design. The Kleinhans chair represents an important point in Charles's career because it was the first expression of his notion of wringing a solution from a single piece of material--a single-shell chair."