“Police said Friday that the fact that a body washed up on a Wilmette beach had two left thumbs could help them identify the man.”

This intriguing page 15 filler item in the April 12 Tribune went on to list the floater’s more conventional attributes–five foot four, 170 pounds, 30 to 40 years old, African-American–without bothering to explain how he picked up the extra digit.

His parents handed it down. Polydactyly is a congenital defect resulting in extra fingers or toes that can be well formed and functional or just tiny nubbins of flesh. Sometimes doctors tie string around them until they fall off. The condition shows up in about one in 500 newborns, though more frequently in African-Americans, Amish, and cats. Polydactyls often suffer no other liabilities than exemption from military service and can count among themselves, legend has it, such notables as Winston Churchill and Charles VIII of France.

Preaxial (thumb) polydactyly, however, can accompany a number of genetic diseases, including Holt-Oram syndrome, which burdens children with heart defects, and Fanconi’s syndrome, a kidney disease that stunts growth and can cause rickets.

But an extra thumb is common enough that after the story ran the Wilmette police took calls from acquaintances of several polydactyls, only one of whom turned out to be missing. They aren’t saying who he is until a DNA test confirms it, but they’re pretty sure they’ve fingered him.