Science confirms: Boston cats are more likely to be polydactyl.
In other words, Boston has a very high rate of cats with extra toes — so much so, that the trait has developed a nickname: "Boston thumb."
The question is: why? The most likely explanation is that decades ago, sailors in New England developed an affinity for the extra-toed cats. They were thought to be better climbers (to catch rodents) and just plain good luck. The trait was artificially selected for, and a result, Boston has a much higher rate of polydactylism than other U.S. cities.
(Another nickname for these cats is "Hemingway Cats" — apparently, the author Ernest Hemingway collected more than 50 of them while living in Key West.)
For one more week, Boston's MSPCA is running a promotion for senior cat adoption, complete with a poster for Catsablanca.