Snakes may be creepy, but they are also a poignant example of the power of evolution. According to a report from UPI, a groundbreaking new study may have figured out why snakes ditched their arms and legs in the first place.

Researchers from the University of Edinburgh in Scotland have compared modern snake skulls with fossilized samples as old as 90 million years to try and figure out what could have precipitated the shift towards a limbless body. They think that it may have had something to do with snakes’ penchant for burrowing underground.

The researchers used CT scans to examine the inner ear cavity of a fossilized species called Dinilysia patagonica. They found that the ancient snake’s ear canal was strikingly similar to modern snake species that spend the majority of their time burrowing underground.

According to the study’s lead researcher Dr. Honguy Yi from the University of Edinburgh’s School of Geosciences, the discovery may be the first real hint into how snakes began evolving to live without arms and legs. The inner ear can tell scientists a large number of things about the way the snake interacted with its environment, and it is usually well preserved in skull fossils across the epochs.

An earlier Yale study this year offered strong evidence that snakes had evolved on land, and not in the water as researchers once believed. Scientists think that the most recent common ancestor for all living snakes was a serpent-like creature with tiny rear limbs that lived 128 million years ago.

A press release from the University of Edinburgh describing the details of the study can be found here.