The extinction event at the end of the “Age of Dinosaurs” saw a rapid evolution of bird genomes, according to a new study.
At the end of the Cretaceous period, 66 million years ago, an asteroid crashed into Earth, triggering the mass extinction. Almost all animals weighing more than 25kg were wiped out. This included all the non-avian dinosaurs – that is, those dinosaurs which did not evolve into modern birds.
Analysis of living bird species’ DNA has been published in the journal Science Advances.
It shows evidence of “genomic fossils” in birds. These are markers of critical evolutionary steps as the roughly 10,000 species of birds alive today evolved from feathered dinosaurs.
“By studying the DNA of living birds, we can try to detect patterns of genetic sequences that changed just after one of the most important events in Earth’s history,” says lead author Jake Berv, from the University of Michigan, USA. “The signature of those events seems to have imprinted into the genomes of the survivors in a way that we can detect tens of millions of years later.”
Major shifts in bird genomes in the aftermath of the mass extinction include those which appear to be connected to how baby birds develop, adult size and metabolism.
One such shift occurred about 3–5 million years after the end-Cretaceous extinction. At this time, birds tended to develop smaller bodies.
More bird species also developed to be altricial, meaning that babies are still very embryonic when they hatch and need their parents to feed and take care of them for weeks.
“We found that adult body size and patterns of pre-hatching development are 2 important features of bird biology we can link to the genetic changes we’re detecting,” Berv adds.
The analysis was made possible by a new software tool which allows researchers to model which genetic changes were most likely to be associated with different traits.
It follows another genetic study of modern birds which hinted at a rapid growth of bird diversity in the aftermath of the end-Cretaceous extinction.
“We know that mass extinction events can dramatically affect biodiversity, ecology and organismal form,” says co-author Daniel Field, from the University of Cambridge, UK.
“Our study emphasises that these extinction events can actually influence organismal biology even more profoundly – by altering important aspects of how genomes evolve.
“This work furthers our understanding of the dramatic biological impacts of mass extinction events and highlights that the mass extinction that wiped out the giant dinosaurs was one of the most biologically impactful events in the entire history of our planet,” Field adds.
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