Dinosaurs: birds can say thank you – TF1

Most of the more than 10,000 species of birds appeared “promptly” after the extinction of dinosaurs and not millions of years ago, shows a large genomic study also sheds new light on their evolution and that of humans. This work for four years by an international team of 200 scientists from twenty countries have sequenced the genome of 48 major avian species (ostrich, duck, hawk, parrot, ibis, eagle …), which is unprecedented for one animal family. They resulted in 28 studies, eight of which were published Thursday in the journal Science.

They demonstrate that only a few species of birds survived the extinction of the dinosaurs there are 66 million years and other Animal then went through a kind of “big bang”, that is to say an accelerated evolution for the emergence in less than fifteen million years of spectacular avian diversity. This contradicts the hypothesis advanced so far that the so-called modern birds had appeared 10 to 80 million years before the dinosaurs disappeared. One of these studies also allowed to go back to the common ancestor to birds, crocodiles –leur closest cousin Shown– and Dinosaurs: archosaurs.

Humans and birds have the same genes sound

The scientists also found that the chicken shared more similarities in its chromosomes with dinosaurs than other birds. According six other studies, some species of birds have the same genes as humans for learning sounds. “We have long known that there are similarities between birdsong and human speech but we did not know if the same genes were involved … and the answer is yes,” said Erich Jarvis, a researcher Duke University (North Carolina). Japanese researchers have identified more than 50 genes undergo similar changes with the activity of specialized brain circuits in learning the sounds of some birds (hummingbirds, parrots and passerine) and the regions of speech in the human brain.

The sequencing of these genomes also revealed that the birds that survived the dinosaurs have lost their teeth there are about 116 million years with mutations in five genes encoding production enamel and ivory. This new family tree of birds also resolves long-standing debate on the relationship between species and their origins. These works allow for example to confirm that waterfowl have three separate origins and that the common ancestor of terrestrial birds (parrots, woodpecker, owl, eagle, hawk …) was a large predator. Despite the biological diversity of birds, their genome contains fewer genes (approximately 14,000) than other major animal families.

This study, conducted in particular by Guojie Zhang of the National Genebank in China, it was discovered that the genome of birds lost thousands of genes at the beginning of their evolution shortly after diverged from other reptiles. “A lot of these genes (lost by birds) have essential functions in humans as in reproduction, the formation of the skeleton and lungs,” said Professor Zhang. “The loss of these key genes could have had a significant effect on the evolution of many characteristics of birds.” “This is interesting because it is generally expected that the development of innovation results from the creation of new genetic material, no loss …”, he added. But after the loss of genes early in their evolution, avian genome structure has remained remarkably stable for more than a hundred million years, the researchers concluded. While at the same time, the mammals have evolved much more important. The mass of data produced by the sequencing of the genomes of 48 species has required 300 years time computer calculation, some analyzes have required supercomputers.