New research led by the American Museum of Natural History reveals that the evolution of modern birds was greatly shaped by the history of our planet’s geography and climate.
Published today in the journal Science Advances, the study finds that birds arose in what is now South America around 90 million years ago, and moved around the world near the time of the extinction that killed off the non-avian dinosaurs. This new research suggests that birds in South America survived this event, moving to other parts of the world via multiple land bridges and becoming more diverse during periods of global cooling.
“Modern birds are the most diverse group of terrestrial vertebrates in terms of species richness and global distribution, but we still don’t fully understand their large-scale evolutionary history,” said Joel Cracraft, a curator in the Museum’s Department of Ornithology and co-author of the paper. “It’s a difficult problem to solve because we have very large gaps in the fossil record. This is the first quantitative analysis estimating where birds might have arisen, based on the best phylogenetic hypothesis that we have today.”
Cracraft and lead author Santiago Claramunt, a research associate in the Museum’s Department of Ornithology, combined DNA sequences for most modern bird families with those of 130 fossil birds to generate a new evolutionary time tree.
“With very few exceptions, fossils of modern birds have been found only after the Cretaceous-Paleogene (K-Pg) extinction,” said Claramunt. “This has led some researchers to suggest that birds didn’t start to diversify until after this event, when major competitors were gone. But our new work, which agrees with previous DNA-based studies, suggests that birds began to radiate before this massive extinction.”