November 23, 2009
the birth of a species
Studying the migration of a finch on the Galapagos Islands, a husband and wife team have documented the moment when a new species was born.
In the tradition of finches, for whom songs are passed from father to son and used to serenade potential mates, the sons learned their immigrant father’s tunes. But their father’s vocalizations were strange: he’d tried to mimick the natives, but accidentally introduced new notes and inflections, like a person who learns a song in a language he doesn’t understand.
These tunes set the sons apart, as did their unusual size. Though they found mates, it may only have taken a couple generations for the new lineage to ignore — or be ignored by — local finches, and breed only with each other. The Grants couldn’t tell for certain when this started, but they were certain after four generations, when a drought struck the island, killing all but a single brother and sister. They mated with each other, and their children did the same.
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