Friday, 1 July 2016

Hairy shells and feathers

What do your hair and a turtle’s shell in common? An ancestor. Nicolas Di-Poï and Michel Milinkovitch have found the common ancestor of hair and shells.

No missing-link
A common origin of shells and hair used to be quit a controversial idea. There are a couple of reasons for this. Firstly, no proper ‘missing-link’ has been found. There is no trace of fossils that had a skin covered with something between shells and hair. When such a missing link is found, it’s usually a strong sign that the two traits, shells and feathers for example, have a common origin. So did the dinosaur Archaeopteryx, which is basically half dinosaur half bird, prove that birds originate from dinosaurs. Another problem for the feathers, hair and shells is the fact that these three things are very different in their chemical make-up. It’s a bit like trying to find a common origin for your cat and your bed. These two things are the reason that scientists have thought that hairs and shells evolved independently of each other for a long time. Two scientists have discovered that this assumption is wrong.

Looking at baby crocodiles
Bearded dragon
Nicolas Di-Poï and Michel Milinkovitch have discovered this common origin by studying the embryos of crocodiles, snakes and bearded dragons. They analysed the unborn animals at different stages and with this, they were able to find out how the shells developed. From this discovery, they concluded that shells, hair and feathers are homologous. That means that they have a common origin, like your arms and a dolphin’s front fins have too, although they don’t look the same. Hair and feathers are formed from an earlier stage of shells because of special proteins called signalling proteins. These proteins are formed by DNA and they influence the growth of, in this case, shells. Different animals have different DNA, so they form different proteins, which changes if they have either feathers, hair or shells. And that’s why you’ll never see a hairy turtle.

One big family
This discovery tells us more about the origin of reptiles, mammals and birds, and how they’re all related. And, while a missing link between hair and shells hasn’t been found yet, it’s pretty sure that one must exist because of this new discovery. That is, however, a thing for archaeologists to find, as fossils of it must still be buried somewhere. On top of that, you might be a bit dinosaur after all, with your hair being related to their shells.

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