About 66 million years ago, at the end of the Cretaceous period, a 10-km-wide asteroid crashed into Earth near the site of the town of Chicxulub in what is now Mexico. The impact eradicated roughly 75% of the animal and plant species on Earth, including whole groups like non-avian dinosaurs and ammonites. New research has identified important changes in birds’ genomes sparked by this end-Cretaceous mass extinction, ultimately contributing to the...
