November 2019, ScientificAmerican.com 59Winged
Victory
The discovery of a strange
chromosome in songbirds
might explain their
astonishing diversity
By Kate Wong
SONGBIRD SPECIES found to have the extra chromosome
include the Gouldian finch ( 1 ), Blyth’s reed warbler ( 2 ),
Eurasian skylark ( 3 ), Eurasian bullfinch ( 4 ), rook ( 5 ),
European siskin ( 6 ), common canary ( 7 ), pine bunting ( 8 )
and barn swallow ( 9 ).W
hen a 10 -kilome-
ter-wide hunk
of burning space
rock slammed
into what is now
the Gulf of Mexico
66 million years
ago, it touched off widespread destruc-
tion, wiping out more than 75 percent of
life on Earth. The Chicxulub asteroid, as
it is called, is best known as the dinosaur
killer. But although it doomed Tyranno-
saurus rex and Triceratops, the sauro-
pods and the hadrosaurs, the asteroid
actually set one lineage of dinosaurs on
a path to glory: that of modern birds.EVOLUTION3
6
9
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