Are dinosaurs and birds related? Very much so, according to Harvard's Arkhat Abzhanov. In fact according to Abzhanov, birds are baby dinosaurs. It was all a matter of timing.

The evolution from dinosaur to bird was the result of a drastic change in how the dinosaur developed that gave way to the evolution of birds.

Abzhanov says in his research, “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 study was sparked by the realization that the skulls of modern birds and those of juvenile dinosaurs were remarkably similar. Harvard co-researcher Bhart-Anjan Bhullar spoke of that realization, “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.”

Using a rather unusual methodology, the researchers employed CT scanners to scan dozens of skulls from modern birds, through to the skulls of therapods, the sub-order that is widely believed to be the dinosaur most closely related to birds. Using this method, the researchers were able to track the changes that took place to the skull of the creatures through millions of years. Throughout the study, they took as landmarks, the cranial cavity, orbits and other skull features to make their determination.

“We examined skulls from the entire lineage that gave rise to modern birds,” Abzhanov said. “We looked back approximately 250 million years, to the Archosaurs, the group which gave rise to crocodiles and alligators as well as modern birds. Our goal was to look at these skulls to see how they changed, and try to understand what actually happened during the evolution of the bird skull.”

According to Abzhanov and his colleagues, what they found was surprising. They found that as dinosaurs matured, they go through a broad array of changes, but the skulls of juvenile dinosaurs and adult birds remained remarkably similar.

The research determined that modern birds are a result of a process called progenesis, which causes an animal to reach sexual maturity earlier. Unlike their dinosaurian ancestors, that many times took years to reach maturity, modern birds take dramatically less time, in some cases, just 12 weeks in many species, to reach maturity, allowing birds to retain the characteristics of their juvenile ancestors into adulthood.

The development of birds in this manner highlights the diversity of evolutionary strategies that have been used over millions of years.

“That you can have such dramatic success simply by changing the relative timing of events in a creature’s development is remarkable,” he said. “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.”

“It shows that there’s so much for evolution to act upon,” Bhullar agreed. “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.”