Bats and dolphins trod an identical genetic path to evolve a vital component of the complex sonar systems they use to pursue and catch prey.

The finding is unusual, because although many creatures have independently evolved characteristics such as eyes, tusks or wings, they usually took diverse genetic routes to get there.

Analysis of a specific gene has now demonstrated that although bats live in air and dolphins in water, where sound travels five times faster, they independently evolved a near-identical gene that allows them to accept high-frequency sound in the ear – vital for sonar.

The gene makes prestin, a protein in hair cells of the cochlea, which is the organ in the inner ear where sonar signals are accepted and amplified. Prestin changes shape when exposed to high-frequency sound, and this in turn deforms the fine hair cells, setting off an electrical impulse to the brain. So the protein has the important jobs of detecting and selecting high-frequency sounds for amplification.


When researchers examined the molecular structure of the prestin gene from a range of animals, they found that the variants in echolocating bats and dolphins were virtually indistinguishable. By contrast, the prestin genes from baleen whales, which don’t have sonar, were much more similar to those from cows, to which whales are closely related. Likewise, four non-echolocating bats lacked the “sonar” version.

Prestin this way

The researchers also worked backwards through genetic time to demonstrate that the prestin gene evolved in echolocating bats and dolphins by the same route, gradually picking up the same mutations to get there.

“It means that high-frequency hearing fundamental to echolocation evolved through the same molecular route,” says Stephen Rossiter of Queen Mary, University of London.

Rossiter says the outcome is a “striking example” of evolution through the same genetic route, because echolocation is such a complex trait. Although there have been previous examples, they have been of much simpler characteristics, such as the evolution of the antibacterial enzyme lysozyme to degrade bacterial walls.

Aural menagerie

Rossiter’s team were alerted to the potential importance of the prestin gene to echolocating animals by earlier work showing that in humans, damage to the gene prevents people from hearing high-frequency sounds.

To investigate further, the team looked at the prestin gene from four toothed whales, two baleen whales, 18 bats and a variety of other animals.

“The parallels in echolocation between the bats and the dolphins are striking,” says Brock Fenton, who studies the evolution of bat bones linked with echolocation at the University of Western Ontario in London, Canada. “The story could be further enriched if there were data about prestin genes in echolocating birds and other echolocators, such as shrews,” he says.

Journal reference: Current Biology, DOI: 10.1016/j.cub.2009.11.042