Once upon a time, snakes did have legs

New Delhi: About 150 million years ago, snakes roamed on well-developed legs, which researchers say were lost due to mutations in a genetic switch. Taken together, the mutations in the enhancer of a gene known as “Sonic hedgehog” disrupts a genetic circuit that drives limb growth in snakes.

Scientists made their discovery by studying genetic activity in developing python embryos and by comparing DNA sequences of snake and lizard genomes. While some snakes, such as cobras and vipers, are completely limbless, pythons and boa constrictors have retained some vestiges of their leg structures.

During the past 20 years, other scientists have described snake fossils with functional hind legs outside their rib cages. The fossils are estimated to be 90 million years old, and while at least one of these species likely retains the legs of its limbed ancestors, some believe that legs re-evolved in other snakes.

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