Ever wondered how modern birds emerged and evolved after the mass extinction that wiped out dinosaurs 66 million years ago? The family tree of modern birds has confused biologists for centuries and the molecular details of how birds arrived at the spectacular biodiversity of more than 10,000 species is barely known. Till now.
That story is now coming to light, thanks to an ambitious international collaboration that has been underway for four years.
The Avian Phylogenomics Consortium has so far involved more than 200 scientists from 80 institutions in 20 countries, including the Beijing Genomics Institute in China, University of Copenhagen, Duke University, University of Texas, the Smithsonian Institution and many others.
Researchers mapped the complete set of DNA instructions, or genomes, of 45 bird species representing every group of living birds, as well as representatives of all three groups of crocodilians (American alligator, saltwater crocodile and Indian gharial) – the closest living bird relatives.
> Scientists think birds evolved from small, feathered dinosaurs. The earliest known bird, Archaeopteryx, lived 150 million years ago.
> The new study finds that the rate of change in the DNA of birds began 66 million years ago, coinciding with the extinction of most dinosaurs.
> The surviving dinosaurs then radiated into a constellation of species that led to about 95 per cent of birds on the planet today, says Erich Jarvis, a neurobiologist at Duke University in Durham, North Carolina.
The first findings have been reported in 23 papers – eight papers in a special issue of Science and 15 more in Genome Biology, GigaScience and other journals.
The first flagship paper published in Science presents a well-resolved new family tree for birds, based on whole-genome data. The second paper describes the big picture of genome evolution in birds.
The other six in Science describe 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; how crocodile genomes evolved; ways in which singing behaviour regulates genes in the brain; and a new method for phylogenic analysis with large-scale genomic data.
> Birds have evolved at a relatively rapid rate compared with their reptilian relatives, which have remained more or less unchanged for over 100 million years.
> Researchers also found that the common ancestor to birds, crocodilians, and dinosaurs evolved relatively slowly. This ancestor, in a group called the archosaurs, lived roughly 240 million years ago.
> Researchers were also able to reconstruct about half of the archosaur genome based on what they found for birds and crocodilians.
Compiled by Aleesha Matharu
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