Feathers are one of the most complex features found on animals, but where did they come from?
Scientists now believe that feathers didn’t just appear suddenly in birds.
Instead, they evolved step by step from much simpler structures called proto-feathers, which first appeared in some dinosaurs about 200 million years ago.
Proto-feathers were tiny, tube-shaped filaments—not like the feathers we see on birds today. They didn’t have barbs or barbules (the little branches on feathers that help them stick together), and they didn’t grow from follicles (small pits in the skin).
These simple structures may have helped dinosaurs stay warm or look attractive to others before eventually evolving into the feathers that allow birds to fly.
Some scientists think proto-feathers may have even existed earlier, possibly around 240 million years ago, in the common ancestor of both dinosaurs and pterosaurs (the first flying reptiles with wings like bats).
To understand how feathers developed, researchers in Switzerland, led by Professor Michel Milinkovitch at the University of Geneva, study how feathers, scales, and hair form in embryos.
Their focus is on molecular signaling pathways—systems that allow cells to “talk” to each other during development. One of these pathways is called the Sonic Hedgehog (Shh) pathway.
In a previous study, the team activated the Shh pathway in chicken embryos and turned foot scales into feathers—permanently. This showed that small changes in early development can lead to big differences in appearance.
In a new study, researchers Rory Cooper and Michel Milinkovitch blocked the Shh pathway in chicken embryos just before feather buds began to form. This caused the feathers to grow as simple, unbranched filaments—very similar to proto-feathers in dinosaurs. But something surprising happened. Although the chicks hatched with bare skin, their bodies soon recovered. Hidden feather follicles activated by themselves, and the birds eventually grew normal feathers.
This experiment revealed something important: while it’s fairly easy to trigger the growth of feathers where there were scales, it’s much harder to stop feathers from forming where they’re supposed to grow. Evolution has made the genetic system that builds feathers very strong and hard to break.
The next big question for scientists is: how did these powerful gene networks evolve over time to create something as unique as feathers? Studying these systems may help us better understand how all kinds of new features appear during evolution.
Source: University of Geneva.
