What Do Scales, Feathers And Hair Have In Common?
Scientists have discovered that skin appendages such as scales, feathers and hair evolved from a common ancestor 320 million years ago.
The study was printed in the journal Science Advances. The paper indicates that these different appendages have their roots in a common ancestor of these three diverse lineages. There is similarity on the mechanism behind the embryonic development of scales, feathers and hair, according to Christian Science Monitor.
The scale of the skin of the reptilian creature is developed from structures called placodes, which are tiny bumps of thick tissue found on the surface of developing embryos. The scientists also discovered placodes on the embryos of birds and mammals, wherein they form into feathers and hairs. This was never found on the reptilian embryo before and created controversy about how these features first formed.
Michel C. Milinkovitch, an evolutionary developmental biologist from the University of Geneva in Switzerland and the lead author of the study said that people were fighting about the fact that reptile either lost it or birds and mammals independent developed them. He further said that now they are lucky enough to put this debate to rest because they found the placodes in all reptiles such as lizards, snakes and crocodiles. Milinkovitch and his team then concluded that mammals, reptiles and birds all inherited their placodes from the ancient reptilian ancestor, according to New York Times.
Meanwhile, Richard Prum, an ornithologist at Yale University and who also studied these same developmental structures said that 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.
Dr. Plum explained that they are homologous as appendages. He added that they all use the same signaling system to develop the place where something grows out of the skin, which is more subtle. He further explained that during embryonic development a signaling system tells the skin of an organism to start readying a location to develop an appendage. The scale, hair feather or the tooth grows out of an anatomical structure, which is called placode. This forms the top layer of the skin. Once the signal is sent to a certain location in the skin to develop a placode, the top layer of the skin begins to thicken in that place, as columnar cells that divide more slowly than the normal form.