How Dinosaurs Became Birds

Passed on to me by ABA Events Coordinator and blog contributor George Armistead was this fascinating piece out of the Harvard Gazette reporting on the work done on bird evolution by biologist Arkhat Abzhanov. 

We've known for some time that modern birds are little more than shrunken flying dinosaurs, and one only has to watch squabbling House Sparrows at an outdoor cafe for a brief while to see the tiny Tyrannosaur within, but the actual evolutionary developments that made the change real are unclear.  Enter Abzhanov:

As reported in a May 27 paper in Nature, Arkhat Abzhanov, associate professor of organismic and evolutionary biology, and Bhart-Anjan Bhullar, a Ph.D. student in Abzhanov’s laboratory and the first author of the study, found evidence that the evolution of birds is the result of a drastic developmental change. Rather than take years to reach sexual maturity, as many dinosaurs did, birds sped up the clock — some species take as little as 12 weeks to mature — allowing them to retain the physical characteristics of baby dinosaurs.

“What is interesting about this research is the way it illustrates evolution as a developmental phenomenon,” Abzhanov said. “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.”

You read that right.  Birds are baby dinosaurs.  Using CT scans to get a detailed three dimensional look at bird skulls, as well as those of bird-like theropod dinosaurs, Abzhanov and his team were able to map "landmarks" on the skull and mark how it changed over millions of years. 

The key discovery is that, while bird skulls change very little from hatchling to adult, dinosaurs change a significant amount more.  Moreso, modern birds and baby dinosaurs show a marked similarity in the location of those landmarks. 

So next time you get a good look at a flycatcher hawking insects, or a mockingbird defending its turf, you're seeing something far more primal.  The last of the dinosaurs.