Evolution of Feathers

Feathers are seen only in birds, and all the species have feathers. Interestingly, birds are dinosaurs – in fact, they are the sole surviving lineage in the entire dinosaur family tree. Hence, feathers, can be traced back to the dinosaurs. However, it is important to note that not all species sported feathers.

Functionally, feathers are thought to provide flight as well as insulation. However, since remains of feathers have been discovered in non-flying dinosaurs, the functions of feathers have been extended to waterproofing and even thermoregulation.

Traditionally, feathers are thought to have evolved from reptilian scales – where the scales in the ancestors of birds frayed and spilt, eventually turning into feathers. It was also speculated that the ancestors of birds were small reptilians that lived in the canopies of trees, leaping from tree to tree. If their scales were longer, it would have provided more lift, enabling the organism to glide further and further. Later down the line, the arms would have evolved into wings – transitioning from gliding to true powered flights. However, new research have objections to this idea.

Regardless, feathers in modern birds are brightly colored, which are in response to sexual selection (attracting the opposite sex). Hence, feathers in dinosaurs could have evolved based on the same idea. This speculation gained traction in 2009, when scientists took at a closer look at their structure, revealing microscopic structures called melanosomes. These fossilized, sac-like melanosomes were compared to the melanosomes from living birds.

What they found was very interesting – the melanosomes correspond precisely in shape to structures, which are associated to very specific colours in the feathers of extant birds. What this meant was that the scientists were able to reconstruct the feather’s colours. For instance, the tail of Sinosauropteryx appears to have red and white stripes on its tail. Scientists believe that this may have been used for courtship- where males attracted females. Some scientists also believe that both sexes might have used these stripes the way a zebra uses its stripes – to confuse potential predators.

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