London: Feathers were initially evolved in birds to keep them warm and not for flying, a new study has claimed.
Researchers found that feathers on prehistoric dinosaurs, which later evolved into birds, were arranged in multiple layers to act as insulation and preserve heat.
The study from the Universities of Bristol, Yale and Calgary found that prehistoric birds had a very primitive version of wings, and it was not until millions of years later that they began to evolve for display and camouflage, and then finally to allow the dinosaurs to fly.
Instead of flexible and aerodynamic feathers, the creatures had rigid layers which acted as simple airfoils and could be used for limited gliding, the 'Daily Mail' reported.
However, over millions of years natural selection modified these into highly-effective feathered wings which could rapidly change their span, shape and area.
"We are starting to get an intricate picture of how feathers and birds evolved from within the dinosaurs. We now seem to see that feathers evolved initially for insulation.
Later in evolution, more complex vaned or pinnate feathers evolved for display," researcher Jakob Vinther said.
"These display feathers turned out to be excellent membranes that could have been utilised for aerial locomotion, which only very late in bird evolution became what we consider flapping flight.
"This new research is shedding light not just on how birds came to fly, but more specifically on how feathers came to be the way they are today - one of the most amazing and highly specialised structures in nature," said Vinther.
Researchers looked at two different pre-historic species, the Anchiornis huxleyi a dinosaur, and the Archaeopteryx lithographica, a Jurassic bird, thought to be 155 million years old.
They found that the wings differed greatly from modern day birds and were composed of multiple layers of long feathers.
The study revealed the inability of pre-historic birds to separate their feathers, suggesting that taking off and flying at low speeds may have been limited.
Scientists said the wings were primarily used in insulation, or when needed in high-speed gliding or flapping flight.
Once the feathers had evolved by natural selection the basic wing configuration remained almost the same for 130 million years, researchers said.
As the role of aerodynamics and the mechanics of flight became more apparent, birds developed wings which included a layer of long, asymmetrical flight feathers with short covert feathers on top.