Bats and dolphins have something in common: They both use "echolocation," or sonar, to navigate the air and water. Now two scientific breakthroughs help explain how these animals' extraordinary abilities evolved, and how they work.
Research published in this week's issue of Nature creates a better understanding of the manner by which bats use echolocation. The sounds for the bats' built-in sonar is created in two different ways depending on specie: for some, the clicking is produced via the tongue, but other species emit it from the larynx. It turns out that this latter group also have a stylohyal bone, which connects their larynx to the bones surrounding the ear drum. This structure was identified through micro-CT scans, and for the first time allows researchers to identify the source of a bat's biosonar through skeletal remains. This creates a situation where ancient and fossil remains can possibly be understood better, and we can gain greater knowledge of what point in the animals' evolution echolocation arose.
In the most recent issue of Current Biology, a group of scientists from Queen Mary, University of London analyzed the mechanisms of echolocation in both dolphins and bats, and found that not only is this skill an example of convergent evolution, but occurred through the same genetic mutation. Both animals evolved same specialised form of inner-ear hair cells that allow them to echolocate. The genetic change occurred in the Prestin gene, which describes proteins found in the inner-ear hair cells of all mammals. The mutation most likely allows the hair cells to vibrate faster, and pick up higher frequencies. Researcher Stephen Rossiter said "The fact that it is the very same genetic changes that occurred twice in nature suggests that there might be a limited number of evolutionary routes to high frequency hearing in mammals". I say: now we know what to tweak to give us all sonar.