Scientists De-Evolve Chicken to Have Dinosaur Feet

Birds are a lot like dinosaurs. Now, scientists have discovered how dinosaur feet, which had back toes that were non-opposable, evolved into the thumb-like opposable toe of birds.

"This is one of the clearest examples of how indirect and morphological consequences of genetic change are mediated," said Gunter Wagner, evolutionary geneticist, in a news release.

Bird embryos move a lot inside the egg during development. In this case, the researchers found that this movement and the onset of movement at this toe coincided with the twisting of its base. In addition, in the toe, genes of cartilage maturation were expressed at a much later stage than in other digits. In fact, it retains many rapidly dividing stem cells for a much longer period. Such immature cartilage is highly plastic and easily transformed by muscular activity.

So what does this mean? The twisting of the toe is a result of mechanical forces imposed on it by the embryonic musculature.

Intrigued by this, the researchers decided to test their theory. The scientists applied Decamethonium bromide, a pharmacological agent capable of paralyzing embryonic musculature. In the end, the researchers created a chicken with a non-opposable toe with a straight, non-twisted base identical to that of their dinosaur ancestors.

Evolutionary research often centers on mutations, but this new study reveals that the development and evolution of the perching toe cannot be understood without the forces of embryonic muscular activity.

"This is one of the clearest examples of how indirect the morphological consequences of genetic change are mediated," said Wagner. "The experiments prove that interactions about organ systems channel the directions of organismal evolution."

The findings are published in the journal Scientific Reports.

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