From dinosaurs to birds: The mysterious origin of feathers

Birds and feathers are closely tied together – feathers enable flight, provide insulation, and make courtship displays possible. Yet the origin of these remarkable structures predates birds.

Feathered dinosaurs were first reported in the 1990s, but many mysteries remain about how and when feathers emerged. Did all dinosaurs share a feathered ancestor, or did feathers appear multiple times in different lineages? 

A new study co-authored by Paul Barrett and Xu Xing from the Natural History Museum attempts to consolidate the latest knowledge and move us closer to an answer.

Feathers of the distant past

Fossil evidence has revealed that feathers are not exclusive to modern birds and their immediate relatives. Dinosaurs with feathers existed in the distant past, showing that these structures are much more ancient than once believed. 

However, broad questions endure: Are feathers found only in meat-eating theropods close to birds, or could they have been more widespread across the dinosaur family tree?

“While dozens of feathered dinosaurs have been identified since Sinosauropteryx was first unveiled in the 1990s, they’re mainly meat-eaters that are close relatives of birds,” Barrett explained. “Everyone agrees that these dinosaurs had feathers, but there’s little consensus beyond that.”

“To settle these disagreements, we need more fossils and to define what a feather is. If we can sort this out, it could reveal where feathers first came from and whether they predate the dinosaurs themselves.”

Conflicting theories on feather origins

Some scientists propose that feathers originated in a common ancestor of dinosaurs and pterosaurs, suggesting all later descendants inherited the potential to grow feathers – though some lost it over time. 

Others argue that pterosaurs did not have true feathers, meaning the structures observed on them might be something else. A third viewpoint holds that feathers emerged solely within theropods, the group that includes well-known predators like Velociraptor and Tyrannosaurus.

To resolve these debates, better fossil evidence from earlier time periods is essential. Most known feathered dinosaur fossils date to the Cretaceous, yet feathers may have evolved well before then. 

Finding older specimens could clarify whether feathers appeared at the dawn of dinosaur evolution or surfaced in only one branch of the family tree.

Did early dinosaurs have feathers?

Professor Barrett emphasized the importance of discovering prehistoric remains from much earlier geological periods. 

“We need to find new sites with fossilized feathers, particularly from the Jurassic and the Triassic,” he said. “The Triassic is especially important, as finding feathered dinosaurs at this early time in dinosaur evolution would suggest that all dinosaurs had an ancestor with feathers.”

“If feathered dinosaurs aren’t found among early dinosaurs, then it makes it more likely feathers were an innovation among later groups.”

Such discoveries could shift perceptions of the entire dinosaur lineage. Were feathers a universal trait that some species shed over time, or did they evolve independently in separate groups?

Defining a “true feather”

Another challenge paleontologists face involves the definition of a “true feather.” Modern bird feathers have distinct chemical and structural characteristics, including growth from a follicle in the skin. Ancient dinosaur feathers may have looked different, reflecting earlier evolutionary stages.

“To identify a true feather from a living bird, we’d look to see what it’s made out of, and its structure,” Barrett explained. “One of the characteristics we have to identify is that the feather grows out of a follicle in the skin.”

“It’s possible, however, that follicles and other modern characteristics might not have been present in all dinosaur feathers. Detailed anatomical work at a microscopic level to compare preserved skin and feathers with examples from living birds could help to resolve this.”

Fossilized skin can also offer important clues. Some specimens display bird-like tissues, hinting that the common ancestor of certain dinosaurs and birds shared these traits. 

But other dinosaurs show more reptilian textures, indicating the possibility that feathers evolved separately in multiple lineages.

Unraveling the history of feathers

For the moment, experts remain divided on how feathers took hold in dinosaur evolution. The challenge lies in discovering enough well-preserved fossils from the right time periods and reaching a clear consensus on what counts as a feather. 

From tantalizing glimpses in existing fossils to ongoing searches in promising new sites, researchers continue to piece together this ancient puzzle.

Ultimately, answers about the origins of feathers may transform how scientists understand dinosaur evolution – and the emergence of birds. 

Until then, paleontologists will continue to search the world for the fossils which can finally settle this decades-old debate. Each new find has the potential to reshape our perception of the prehistoric world and the ancestors of the birds we see in our skies today.

The study is published in the journal Biology Letters.

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