Most toes

Polydactyly – the presence of extra fingers and toes – is especially common in cats. And it’s all thanks to Ernest Hemingway and Sonic the Hedgehog.

Polydactyl cat
Howie831 / CC BY-SA

Most cats have five toes on each front paw and four toes on each rear paw, for a total of 18 toes. Polydactyl cats have more: the record is 28 toes total. That’s a lot of toes! (The human with the most toes, born in India in 2010, had a measly 20 toes in all.)

Ernest Hemingway was a big fan of polydactyl cats and actually collected them. About fifty descendants of those cats still live in a former house of his in Florida. According to Wikipedia, fully half of those cats have excess toes.

Where does feline polydactyly come from? Well, it’s all thanks to a mutation in a gene that regulates the gene Shh. Shh is crucial for animal growth: the protein encoded by Shh influences brain structure and development, as well as teeth, lungs, arms, legs, fingers, toes, and a whole bunch more. Problems with this gene can also cause embryos to develop many little bumps, making them look a little like a baby hedgehog… and so the protein produced by Shh is known as Sonic hedgehog.

I’m not even kidding – that’s its actual official scientific name. There are a few equally odd protein names out there, including one named after Pikachu, but maybe that’s a post for another time.

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