When feather really took flight

Washington, Feb 12 (ANI): The molecular structure of the modern feather began to take form some 125 million years ago - more recently than once thought.

This is the finding of a molecular dating research by scientists at the University of South Carolina.

The team also sees hints that powered flight might be the innovation that drove the feather's evolution from that point forward.

Feathers are largely made of proteins, and particularly of beta-keratin, which is also found in the scales and claws of birds, as well as related species like crocodiles and anoles, the small green lizard common throughout the southeastern United States.

Roger Sawyer, a biologist in USC's College of Arts and Sciences, has been studying the details of the bricks made of beta-keratin since the early 1970s; his approach has been molecular, using biochemistry and immunology to access new data as innovations in laboratory tools became available over the years.

By looking at the kind of beta-keratin found in scales, claws, and feathers in modern animals, for example, Sawyer's lab has grouped certain sequences into families, defined in a straightforward manner as scale, claw, and feather beta-keratins.

And, thanks to recent advances in genetic sequencing, the full genomes of several modern animals are now available, including the zebra finch, the chicken, and the turkey.

The fossil record shows that the zebra finch and the chicken began diverging about 100 million years ago, and their gene sequences offer a comparison of how far their genomes have diverged since emerging from a common ancestor.

By comparing the details of how the gene sequences for the beta-keratins are now arranged in the genomes of modern animals with how much time it has taken for those species differences to arise, Sawyer's group has developed new insight into how and when the beta-keratin families developed.

And as Sawyer and post-doc Matthew Greenwold reported in December in the Journal of Experimental Zoology, one big surprise was that the evolution of the family of feather beta-keratins doesn't appear to coincide with the evolutionary origin of feathers themselves.

The fully feathered fossil of Anchiornis huxleyi, for example, is 155 million years old, yet Sawyer's results point to the family of feather beta-keratin just beginning to develop its distinguishing characteristics about 143 million years ago.

Moreover, about 125 million years ago, there began a dramatic expansion of feather beta-keratin sequences throughout the genome.

They have also shown that the scale and claw families of beta-keratin emerged earlier than that, concluding that the first feathers comprised beta-keratins more similar to those now found in scales and claws-a more primitive feather, in a sense. (ANI)