At first glance, it's hard to see how a common house sparrow and a Tyrannosaurus Rex might have anything in common. After all, one is a bird that weighs less than an ounce, and the other is a dinosaur that was the size of a school bus and tipped the scales at more than eight tons.
For all their differences, though, scientists now say that two are more closely related than many believed. A new study, led by Harvard scientists, has shown that modern birds are, essentially, living dinosaurs, with skulls that are remarkably similar to those of their juvenile ancestors.
As reported in a May 27 paper in Nature, Arkhat Abzhanov, Associate Professor of Organismic and Evolutionary Biology and Bhart-Anjan Bhullar, a PhD student in Abzhanov laboratory and the first author of the study, found evidence that the evolution of birds is the result of a drastic change in how dinosaurs developed. 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."
"The evolution of the many characteristics of birds things like feathers, flight, and wishbones has traditionally been a difficult problem for biologists," Mark Norell, chair of the Division of Paleontology at the American Museum of Natural History and one of the paper's co-authors, said. "By analyzing fossil evidence from skeletons, eggs, and soft tissue of bird-like dinosaurs and primitive birds, we've learned that birds are living theropod dinosaurs, a group of ca
|Contact: Peter Reuell|