There is a Likelihood Snake May Grow Limbs as they Have the Genes to do so

For those with ophidiophobic (from ophiophobia is the irrational/abnormal fear of snakes) this piece of information may not be a good one for you. Imagine waking up to snakes on legs? Scary right?



^{National Geographic: Tetrapodophis catching a lizard.}


About 150 million years ago, snakes used to have four limbs. The tetrapodophis which translate to four-footed snake in Greek roamed Brazil with the dinosaurs. But some genetic mutation caused the reptiles to lose their legs.

But snakes have the gene to grow legs. The gene is referred to as the Sonic Hedgehog Gene. This gene was so-named due to the hedgehog-like spines seen on embryos during the start of limb development. How the gene got Sonic to its name is an intriguing one.

One of the researchers in the Harvard lab, Robert Riddle, working on the first cloning of the Sonic Hedgehog gene got the name from a comic book that the daughter had during the time of paper was being published. The Sonic The Hedgehog was a 1991 Sega game.

The Sonic Hedgehog (SHH) gene is important in the development of limbs as it acts like a motor that controls the development of limbs. The SHH gene is also behind the tiny claw-like objects that could be seen on a python's skin.

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How Snake Lost Their Legs

A journal published in October of 2016 Loss and Re-emergence of Legs in Snakes by Modular Evolution of Sonic hedgehog and HOXD Enhancers showed that mutation in the Zone of Polarizing Activity Regularity Sequence or ZRS is a snake DNA responsible for the limb-altering change.

They ran a clinical trial where this ZRS DNA was removed from mice embryos and had it replaced by snake's own. The mice were found to have difficulty/inability to grow limbs. This result indicates that ZRS is important in the development of limbs according to the researchers.

"This is one of many components of the DNA instructions needed for making limbs in humans and, essentially, all other legged vertebrates. In snakes, it's broken," the study's senior author Axel Visel, a geneticist at the Lawrence Berkeley National Laboratory in California^Source

There is a sort of enhancer or switch if you may, that controls the SHH gene to either be on or off. In snakes, this switch due to mutation is on "off" position preventing limb development.

There are moments there is a flicker and there is an "on" moment and that is when we see the development of such "claws" (pseudo-limbs) in the underbelly of some pythons.

This means we are likely looking at the possibility of having snakes with a limb without an entire evolutionary circle. Scary right? Share your thoughts below.

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Ref: 1,2,3