Birds are baby dinosaurs-Harvard scientists

Tuesday, May 29, 2012

Birds and dinosaurs are more closely related than previously thought, say scientists who claim that modern birds are, essentially, living juvenile dinosaurs. According to Harvard's Arkhat Abzhanov, Associate Professor of Organismic and Evolutionary Biology, the evolution of birds is the result of a drastic change in how dinosaurs developed. Rather than taking years to reach sexual maturity, as many dinosaurs did, birds sped up the developmental clock, allowing them to retain the physical characteristics of baby dinosaurs.
Abzhanov says the research, appearing in Nature, illustrates evolution as a developmental phenomenon. "By changing the developmental biology in early species, nature has produced the modern bird - an entirely new creature - and one that, with approximately 10,000 species, is today the most successful group of land vertebrates on the planet."
Harvard co-researcher Bhart-Anjan Bhullar explained how it was the realization that the skulls of modern birds and juvenile dinosaurs are surprisingly similar that sparked the study. "No one had told the big story of the evolution of the bird head before," said Bhullar. "There had been a number of smaller studies that focused on particular points of the anatomy, but no one had looked at the entire picture. What's interesting is that when you do that, you see the origins of the features that make the bird head special lie deep in the history of the evolution of Archosaurs, a group of animals that were the dominant, meat-eating animals for millions of years."
For modern birds, Abzhanov says, the change is the result of a process known as progenesis, which causes an animal to reach sexual maturity earlier. Unlike their dinosaurian ancestors, modern birds take dramatically less time - just 12 weeks in some species - to reach maturity, allowing birds to retain the characteristics of their juvenile ancestors into adulthood. How the bird skull evolved through changes in the developmental timeline highlights the diversity of evolutionary strategies, Abzhanov claims. "That you can have such dramatic success simply by changing the relative timing of events in a creature's development is remarkable. We now understand the relationship between birds and dinosaurs that much better, and we can say that, when we look at birds, we are actually looking at juvenile dinosaurs."
"There's so much for evolution to act upon," Bhullar added. "When we think of an organism, especially a complex organism, we often think of it as a static entity, but to really study something you have to look at its whole existence, and understand that one portion of its life can be parceled out and made into the entire lifespan of a new, and in this case, radically successful organism."

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