A new study in the journal Current Biology, shows that the familiar anatomical features of birds – such as feathers, wings and wishbones – all first evolved piecemeal, over tens of millions of years, in their dinosaur ancestors.
However, once a fully functioning bird body shape was complete, an evolutionary explosion began, causing a rapid increase in the rate at which birds evolved.
Based on their findings from fossil records, researchers say the emergence of birds some 150 million years ago was a gradual process, as some dinosaurs became more bird-like over time.
Steve Brusatte of the University of Edinburgh’s School of GeoSciences led the study. He said:
There was no moment in time when a dinosaur became a bird, and there is no single missing link between them. What we think of as the classic bird skeleton was pieced together gradually over tens of millions of years. Once it came together fully, it unlocked great evolutionary potential that allowed birds to evolve at a super-charged rate.
The team of researchers examined the evolutionary links between ancient birds and their closest dinosaur relatives. They did this by analyzing the anatomical make-up of more than 850 body features in 150 extinct species, and used statistical techniques to analyze their findings and assemble a detailed family tree.
Steve C. Wang, Associate Professor of Statistics at Swarthmore College is part of the research team. He said:
The evolution of birds from their dinosaur ancestors was a landmark in the history of life. This process was so gradual that if you traveled back in time to the Jurassic, you’d find that the earliest birds looked indistinguishable from many other dinosaurs.
Birds as we know them evolved over millions of years, accumulating small shifts in shape and function of the skeleton. But once all these pieces were in place to form the archetypal bird skeleton, birds then evolved rapidly, eventually leading to the great diversity of species we know today.
Findings from the study support a controversial theory proposed in the 1940s that the emergence of new body shapes in groups of species could result in a surge in their evolution.
Bottom line: Familiar anatomical features of birds such as feathers, wings and wishbones all first evolved piecemeal, over tens of millions of years, in their dinosaur ancestors. However, once a fully functioning bird body shape was complete, an evolutionary explosion began, causing a rapid increase in the rate at which birds evolved.
Eleanor Imster has helped write and edit EarthSky since 1995. She was an integral part of the award-winning EarthSky radio series almost since it began until it ended in 2013. Today, as Lead Editor at EarthSky.org, she helps present the science and nature stories and photos you enjoy. She also serves as one of the voices of EarthSky on social media platforms including Facebook, Twitter and G+. She and her husband live in Tennessee and have two grown sons.