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From Fins to Wings
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Photo caption by Jennifer Holland
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From Fins to Wings Gallery Photo

Aequipecten irradians, photographed at Marine Biological Laboratory, Woods Hole

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Bay Scallop
Photograph by Rosamond Purcell

A scallop's blue eyespots, which capture light with a mirrored surface, and the eye found in humans evolved from the same basic light-catching device. Closely related genes govern early development in both kinds of eyes, a sign that they have a common ancestry. "Eye types are so different scientists thought they arose independently," more than 40 different times, says biologist Todd Oakley. "But it's like remodeling a house: You don't have to start from scratch; you just change certain elements." What allowed for those changes? "Duplication was part of it," he says. "If two genes evolve to do the same job, one is free to try something new."

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