Out of nearly 140 surveys put on cars, he received 51 completed questionnaires that were mailed back.
"The fact that 66 percent of the respondents identified Christians as their target audience is the key to interpreting these themes," said Lessl. "The apparent desire to deride this audience seems to be just as important as any serious message they want to communicate."
The messages, as might be expected, were wildly varied and often inconsistent.
"I put the Darwin fish on my car for a number of reasons," said one respondent. "Mainly I did it to annoy the Christian right wing, since they are so fond of putting the fish/Christ symbols on their cars. I also use it to display the symbol of my group, which believes natural processes explain the world around us."
But other respondents did intend a positive message.
"I believe that the Darwin fish sums up my religious beliefs," the respondent said. "I believe in a higher being, God, if you will, but I do not believe that the acknowledgment of such a god excludes scientific and anthropological evidence for either the Big Bang theory or evolution."
Lessl identified numerous themes from the respondents, including the association of Darwin with an ecological view of life; a belief in the superiority of science and scientific knowledge; a simple desire to make a joke; and as a symbol of harmony between science and religion. The meanings, however, may be even more complicated than that.