Genetics Reveal the 'Big Bang' of Bird Evolution Occurred After Dinosaur Mass Extinction
Scientists have managed to learn a bit more about bird evolution after examining the time after the mass extinction that wiped out dinosaurs and almost everything else about 66 million years ago. The findings shed a bit more light on the emergence of modern birds.
Scientists already knew that the birds that survived the mass extinction experienced a rapid burst of evolution. But the family tree of modern birds has confused biologists for centuries and the molecular details of how birds arrived at the spectacular diversity of more than 10,000 species isn't well-known.
In order to learn a bit more about bird evolution, the researchers sequenced, assembled and compared full genomes of 48 bird species. These species included the crow, duck, falcon, parakeet, crane, ibis, woodpecker, eagle and others.
The first round of analyses actually suggested some remarkable new ideas about bird evolution. In addition, the scientists were able to create a new family tree for birds, based on whole-genome data. In fact, the scientists found how vocal learning may have independently evolved in a few bird groups and in the human brain's speech regions, how the sex chromosomes of birds came to be, how birds lost their teeth, and ways in which singing behavior regulates genes in the brain.
"In the past, people have been using 10 to 20 genes to try to infer the species relationships," said Erich Jarvis, one of the researchers, in a news release. "What we've learned from doing this whole-genome approach is that we can infer a somewhat different phylogeny [family tree] than what has been proposed in the past. We've figured out that protein-coding genes tell the wrong story for inferring the species tree. You need non-coding sequences, including the intergenic regions. The protein coding sequences, however, tell an interesting story of proteome-wide convergence among species with similar life histories."
In fact, the new tree resolves the early branches of Neoaves (new birds) and supports conclusions about some relationships that have been long debated, such as the three independent origins of water birds. In addition, it reveals that the evolutionary expansion of Neoaves occurred 66 million years ago rather than blossoming 10 to 80 million years early, as other studies have suggested.
The findings reveal a bit more about bird evolution and have huge implications for further studies. The avian genome consortium is now creating a database that will be made publicly available for future scientists to study.
The findings are published in several papers in the journal Science.
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