The end of the dinosaurs triggered the evolution of bird genomes

Aug. 1 () –

The extinction of non-avian dinosaurs 66 million years ago due to an asteroid impact caused major changes in the genomes of birds that contributed to its incredible diversity.

A study led by the University of Michigan examined the evolutionary trajectory of all major groups of birds and found evidence of “genomic fossils” in bird DNA that mark critical evolutionary steps as birds evolved until it became more than 10,000 living speciesThe research is published as an open access article in the journal Science Advances.

“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,” he said. it’s a statement “The signature of those events appears to have been imprinted on the survivors’ genomes in a way that we can detect tens of millions of years later,” said lead author Jake Berv, who completed the study as a Life Sciences Fellow.

The genome of a living organism consists of four nucleotide molecules, designated by the letters A, T, G, and C. The order of these nucleotides in a genome defines the “blueprint” of life. The DNA code can sometimes evolve in a way that changes the overall composition of DNA nucleotides throughout the genome. These compositional changes are crucial in determining what kind of genetic variation is possible, contributing to an organism’s evolutionary potential, or its ability to evolve.

Researchers discovered that the mass extinction event caused changes in nucleotide composition. They also found that these changes appear to be related to the way the birds develop as babies, their adult size and their metabolism.

For example, roughly 3 to 5 million years after the mass extinction, surviving bird lineages tended to evolve smaller body sizes. They also changed the way they developed as offspring, with more species becoming “altricial.” This means they are still very embryonic when they hatch, needing to be fed by their parents and can take weeks to fledge, Berv says. Birds that are born ready to fend for themselves, such as chickens and turkeys, are called “precocial.”

“We found that adult body size and pre-hatching development patterns are two important features of bird biology that we can link to the genetic changes we are detecting,” Berv said.

Berv says one of the most important challenges in evolutionary biology and ornithology is unraveling the relationships between major bird groups: it is difficult to determine the structure of the tree of life for living birds. Over the past 15 years, researchers have been applying increasingly larger genomic data sets to try to solve the problem.

Previously, researchers used genomic data to study the evolution of bird genomes using statistical models that make strong assumptions. These “traditional” models allow researchers to reconstruct the history of genetic changes, but they typically assume that the composition of DNA – its ratio of A, T, G, and C nucleotides – does not change throughout evolutionary history.