Most predators rely on powerful limbs and a superior sense of hearing and smell to hunt. So why do snakes – some of the most common predators worldwide – have no legs or ears?
Snakes typically hunt in the water or in burrows. Here, having no limbs allows snakes to move faster and fit in tight spaces. Snakes don’t have outer ears, but they do have inner ears that can detect vibrations, which helps them detect the location of their prey.
In the rest of this article, I’ll explain how snakes evolved to have no legs or ears and how this evolutionary process benefits them.
How Did Snakes Evolve To Have No Legs and Ears?
The evolution of snakes is a fascinating process. Research suggests that snakes actually had legs around 150 million years ago. They started evolving to become the legless reptiles we know today approximately 100 million years ago, in the Upper Cretaceous period.
The Sonic Hedgehog Genetic Mutation
The Sonic Hedgehog gene produces a protein that decides the growth of parts of the brain, limbs, and other body parts. It decides the shape and structure of the body and is the main reason why we grow limbs.
According to a study, two scientists discovered that the Sonic Hedgehog gene activates briefly in snakes in the embryonic stage. However, the limbs never fully form because they degrade almost immediately due to the arrest of the gene. This can be seen in pythons, which have small, truncated limbs that indicate where their legs would have been.
The study shows that a trio of genetic mutations in the Sonic Hedgehog gene were the reason snakes developed to be legless. This mutation began around 100 million years ago.
Snakes Evolved To Suit Their Hunting Grounds
Scientists have theorized that the main reason snakes evolved to have no legs or outer ears is to suit their hunting grounds. They mostly hunt in water, sand, or small burrows, where having a compact body helps.
As for the ears, snakes actually have ears, but they’re not as developed as ours. They don’t have outer or middle ears capable of detecting a wide range of sounds. However, they have inner ears that can detect vibrations through their skulls.
The ability to detect vibrations allows them to “hear” quite well in an environment where they’re surrounded by earth or water. Their lack of limbs allows them to move faster in water and fit in small holes in the ground. Thus, their lack of fully formed ears or limbs actually helps them hunt better.
Final Thoughts
Snakes have evolved unusually compared to other predators. However, the lack of limbs and ears actually benefits them in their chosen hunting grounds. It allows them to move faster, fit in small places, and locate their prey using the vibrations around them.
Sources
- Audubon Society of Rhode Island: Why Don’t Snakes Have Legs PDF
- Vice: This is Why Snakes Have No Legs
- Medline Plus: SHH Gene
- National Public Radio: How Snakes Lost Their Legs
- Current Biology: Loss and Re-emergence of Legs in Snakes by Modular Evolution of Sonic hedgehog and HOXD Enhancers
- Science Focus Magazine: What evolutionary advantage did snakes gain by losing their legs?
- Smithsonian’s National Zoo and Conservation Biology Institute: Do Snakes Have Ears? And Other Sensational Serpent Questions
- Washington Post: How Snakes Hear Without Ears
- Live Science: Do Snakes Have Ears?
- Futurity: How Snakes Evolved to Lose Their Legs
- British Broadcasting Corporation: Studying How Snakes Got Legless