In addition, the sections of the DNA that usually control how the eyes form have changed in these animals. Since there is less need for a working eye in dark environments, DNA related to the eye is no longer protected from damaging mutations in mammals that live underground. So, by comparing the DNA of mammals that live above ground and underground, scientists can identify the parts of DNA that help form mammals’ eyes.

Previous studies have discovered many sections of DNA responsible for producing the proteins that make up the eye. However, scientists know less about which sections of DNA control when and where these proteins are made. To address this, Raghavendran Partha and colleagues have studied the DNA of four underground mammals: the star-nosed mole, the cape golden mole, the naked mole-rat and the blind mole-rat.

By comparing the DNA of these animals with that of mammals that live above ground, Partha and colleagues identified sections of DNA that contained an abnormally high number of changes in the blind underground mammals. Many of these sections are involved in forming the eye, including controlling when and where proteins are made. Overall, the findings show that comparing rates of evolution in different species can help uncover sections of DNA that guide and influence how organisms develop.

Understanding how the eye is formed is not only of interest to scientists studying evolution and biology; it also has wider applications in healthcare. Many people suffer from unexplained eye abnormalities, and insight into the sections of DNA that control the eye’s development could help medical professionals diagnose these cases and design new treatments.