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Is it possible for feathers, scales and hairs to have anything in common? According to a new paper featured this week in the journal Science Advances, it is. Experts believe that all of these skin appendages could share a common ancestor.
Researchers noted that the mechanism responsible for the embryonic development of a bird’s feathers, a reptile’s scales, and a mammal’s hairs are strikingly similar.
“This doesn’t imply at all that feathers evolved from hair or that scales evolved from hair or that hair evolved from scales, et cetera,” said Richard Prum, a Yale University ornithologist who did not participate in this study.
He went on to explain that these three different developmental structures are “homologous as appendages,” which means they are similar in the way they created the place where something grows out of the skin.
According to Dr. Prum’s research, published previously in 2017, this mechanism is what is shared, the one signaling an organism to prepare certain spots for skin appendages.
Hairs, feathers, and scales – and even a tooth, to a certain degree – grow out of a placode, an anatomical structure that prepares the spot by thickening the top layer of the skin.
Spotting the similarities in placodes between feather and hair development was fairly easy, but experts had a lot of trouble identifying them in scaly reptiles.
This apparent lack of placodes in reptilians led scientists to believe they have lost the feature over time, even if they did have it at some point in their evolution.
The Yale University team, however, managed to find the anatomical placodes in reptile embryos, proving successful where previous research pieces had failed.
In mammals, the placodes appear at the same time over the entire skin; so if researchers took a good look during the embryonic stage, these structures were easily identified. The same does not apply to reptiles, however.
Because the placodes develop at different time intervals on various parts of the reptile’s body, it’s fairly difficult to spot them. It also doesn’t help that they maintain this identifiable state for a very short time – you blink and you might miss it!
Image Source: Good WP
