How closely related are dinosaurs to today's birds? A recent study delves into this issue, investigating how proteins in dinosaur feathers evolved and changed over millions of years and extreme temperatures. Powerful X-rays produced by the SLAC National Accelerator Laboratory are giving researchers new insights into the evolution of feathers.
New research shows that the protein composition of dinosaur feathers is similar to that of modern birds, hinting at the early origins of bird feather chemistry, possibly 125 million years ago. The study found that the α-protein in fossil feathers was likely formed by heat during the fossilization process, rather than originally existing. (Artist's conception of dinosaur feathers).
Previous research has shown that dinosaur feathers contained proteins that made them less stiff than the feathers of modern birds. Now, researchers at University College Cork (UCC), the Stanford Synchrotron Radiation Lightsource (SSRL) at the Department of Energy's SLAC National Accelerator Laboratory, and other institutions have discovered that the original protein composition of dinosaur feathers was very similar to that of modern bird feathers.
This result means that the chemical composition of today's bird feathers may have originated much earlier than previously thought, possibly as early as 125 million years ago.
"It's really exciting to discover new similarities between dinosaurs and birds," said Tiffany Slater, a palaeontologist at UCC and first author of the new study. "Using X-rays and infrared light, we found that the feathers of the dinosaur Sinornithosaurus contained large amounts of beta protein, just like the feathers of today's birds. This finding validates our hypothesis that dinosaur birds had stiff feathers - just like modern birds."
The key is the combination of proteins. Earlier tests on dinosaur feathers found that dinosaur feathers contained mostly alpha-keratin, a protein that makes feathers less stiff, while modern bird feathers are rich in beta-keratin, a protein that enhances the feathers' ability to fly. Still, the researchers wanted to know whether the difference reflected the true chemistry of the feathers during life or whether it was an artifact of the fossilization process.
To find out, Slater and UCC paleontologist Maria McNamara, working with SSRL scientists, analyzed feathers from 125-million-year-old dinosaurs Sinornithosaurus and early bird Confuciusornis, as well as a 50-million-year-old feather from the United States.
To detect proteins in the ancient feathers, the researchers exposed the fossils to SSRL's powerful X-rays, which can show whether key components of beta proteins are present. SSRL scientist Sam Webb says this helps researchers determine whether the beta-protein in a sample is still in its "native" state or has changed over time, and how that change occurs chemically.
Weber said the team also conducted separate experiments simulating the temperatures the fossils were exposed to over time. These experiments suggest that the alpha-protein in the fossil may have been formed during fossilization, rather than being part of the life process of the feather.
The analysis showed that although some fossil feathers contain large amounts of α-protein, they were likely not originally there but developed over time. They were formed because the fossils experienced intense heat.
"Our experiments help explain why this strange chemical difference is the result of protein degradation during fossilization," Slater said. "So while some dinosaur feathers do retain traces of the original beta protein, other fossil feathers contain alpha proteins that were formed during fossilization."
"Raw protein composition may change over time, an often overlooked aspect when studying deep biomarkers," Weber said. "Comparing our X-ray spectroscopy results with additional laboratory measurements of experimentally heated feather samples helps calibrate our findings."
Maria McNamara, senior author of the study, said: "Traces of ancient biomolecules can clearly survive for millions of years, but you can't read the fossil record literally because even seemingly well-preserved fossil tissue has been cooked and squashed during fossilization. We are developing new tools to understand what happened during fossilization and unlocking the chemical secrets of fossils will provide us with exciting new insights into evolution."