The melodious call of many birds comes from an organ buried deep within their chests: a one-of-a-kind voice box called a syrinx. Now, scientists have concluded that this voice box evolved only once, and that it represents a rare example of a true evolutionary novelty.

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The melodious call of many birds comes from an organ buried deep within their chests: a one-of-a-kind voice box called a syrinx. Now, scientists have concluded that this voice box evolved only once, and that it represents a rare example of a true evolutionary novelty.