At Ernest Hemingway’s old home in Key West, Fla., you’ll find bromeliads and date palms, a hand-crafted wooden yacht and an in-ground pool—the only one within 100 miles at the time of its construction. You’ll also find roughly 50 cats, most of which have six toes on their front feet instead of five. As legend has it, after a booze-soaked evening at a local bar, Hemingway was given their six-toed ancestor, “Snow White,” by a waylaid ship captain. On the high seas, these so-called polydactyl cats were cherished for their superior balance and unmatched mousing abilities. Snow White and cats like her also highlight an important concept in neuroscience: the developing brain is flexible enough to wire up to whatever body it finds itself attached to—even if that body is more complex than a “typical” one.

This awe-inspiring flexibility helps the brain translate the extraordinary physical variability among animals—in terms of body size, shape and form—to variability in their behaviors and capabilities. Without it, an animal would not be able to realize the adaptive advantages that come with variability. For example, ancient giraffes with a longer neck had the advantage of being able to feed on higher leaves and so passed the trait on to their descendants. But that neck would have been useless if their brain could not adapt to control it. Likewise, if Michael Phelps hadn’t been able to learn to use his oversize wingspan and feet, he would never have won 23 gold medals.

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