Over 40 ago, Alvarez et al.  provided chemical evidence indicating that the Cretaceous-Paleogene (K–Pg) mass extinction was associated with an extraterrestrial impact. Subsequent research has refined our understanding of how this cataclysmic event influenced biodiversity. Mounting evidence suggests that the K–Pg extinction event triggered convergent patterns of life-history evolution. For example, some lineages may have experienced a transient “Lilliput effect” in which average body sizes became smaller, likely through faunal sorting, dwarfing, or miniaturization

These inferred shifts in substitution patterns were closely related to evolutionary shifts in developmental mode, adult body mass, and patterns of metabolic scaling. Our results suggest that the end-Cretaceous mass extinction triggered integrated patterns of evolution across avian genomes, physiology, and life history near the dawn of the modern bird radiation.