Why were dinosaurs covered in feathers long before the early bird species Archaeopteryx first attempted flight?
Scientists try to answer that in an article in the latest issue of the research journal Science. They propose that these ancient lizards had a highly developed color sensitivity, and that feathers made them more colorful, aiding communication, mate selection and procreation.
The idea that birds and dinosaurs are close relatives dates back to the 1800s, when the father of evolutionary theory, Charles Darwin, was at work. But it took over 130 years for the first real proof to come to light with many discoveries of fossils of feathered dinosaurs, mainly in China.
Thanks to these finds, scientists now believe that birds descend from a branch of medium-sized predatory dinosaurs called theropods, such as Tyrannosaurus rex and also velociraptors, made famous by the film Jurassic Park.
Many of them, including possibly T. rex, had feathers. But why did they, if they couldn’t fly?
“Up until now, the evolution of feathers was mainly considered to be an adaptation related to flight or to warm-bloodedness, seasoned with a few speculations about display capabilities,” said Marie-Claire Koschowitz of the University of Bonn in Germany, an author of the paper.
“I was never really convinced by any of these theories. There has to be some particularly important feature attached to feathers that makes them so unique and caused them to spread so rapidly amongst the ancestors of the birds we know today.”
She now suggests this feature is found in dinosaurs’ color vision. After analyzing dinosaurs’ genetic relationships to reptiles and birds, she concluded that dinosaurs could see not only the colors we can discern, but also ultraviolet.
Mammals generally have rather poor color vision or even none because they tended to be nocturnal during the early stages of their evolution. But many studies on the social behavior and mate choice among reptiles and birds, which are active during the day, have found that they respond to ultraviolet.
The precursors to feathers resembled hairs similar to mammals’ fur, the authors explain. These strands served mainly to help keep the smaller predatory dinosaurs, which would eventually give rise to birds, warm. But they weren’t very colorful. They eventually evolved into flat feathers, which could display of an almost infinite variety of colors while still providing insulation. Their broad surface area, created by interlocked strands of a material called keratin, allows for the bending of light, called refraction, producing color.
“This allowed dinosaurs to not only show off their colorful feathery attire, but to be warm-blooded animals at the same time – something mammals never managed,” said co-author Martin Sander of the university.
Source : www.world-science.net