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Former major league pitcher¹ Antonio Alfonseca had six fingers on each hand. One of his coaches was once asked about the consequences of Alfonseca having six fingers and replied, “He can’t flip² you off.” Think about it.

 

Well, neither can many moles⁴, because most individuals of the type called talpid moles also apparently⁵ have six fingers on each foot. Or at least it looks that way. Now a study shows that they really only have the regular old five true fingers. The real thumb looks like the other four fingers, and what appears to be the thumb is actually a much larger-than-normal version of the radial sesamoid bone of the wrist. The finding is in the Royal Society journal Biology Letters. 

 

The fake thumb has no joints⁶, a dead giveaway that it’s not a real finger. And molecular⁷ markers show that the five true fingers develop together in a mole³ embryo⁸, with the outsized sesamoid cropping up later. The arrangement is probably an advantage for an animal that spends a lot of time digging and doesn’t convey displeasure with hand signals.

 

Thanks for the minute. For Scientific American’s 60-Second Science, I’m Steve Mirsky.

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