The Disappearance of Snake Legs

Snakes have lost their legs about 150 million years ago due to a DNA composition change that created a mutation to get rid of legs. This has been confirmed two separate times by two separate groups of scientists. We know that snakes used to have legs because through dissection experiments of boas and pythons and other snakes, we can find tiny receded bone groups that seemed to be used as legs before.

"Mutations in DNA located near a gene key to limb formation keep that gene rom ever turning on"

The snakes at first were looked at under the mutation of the hedgehog gene that we learned about before in class. So they analyzed the sonic the hedgehog gene and they noticed that there were three deletions and a modified enhancer within snakes. In order to study this enhancer a special technique called CRISPR-Cas9 was used.

"CRISPR-Cas9 is a unique technology that enables geneticists and medical researchers to edit parts of the genome by cutting out, replacing, or adding parts to the DNA sequence"

When the snake enhancer was put into a mouse, the issue was that the mouse grew very stubby legs. When the snake enhancer was repaired with the missing deletions and then put into the mouse, it grew normally. This is molecular genetic evidence for snakes that used to have legs.

I am very excited to see how genetics is now affecting the idea of phylogenies and relationships between animals because for a long time scientists have been using taxonomy in order to project phylogeny, but the only way to truly study relationships is on the genetic and molecular level. Studies like this will continue amending the phylogenies we have developed thus far to be more accurate in telling us how things tacked back to their common ancestors and evolved.