Human Speech and Bat Sonar: The Same Basis

Those bat species that emit ultrasounds to spot prey and avoid obstacles present a high variation in the FOXP2 gene, pointing that mutations in the gene boosted the evolution of the bat sonar. The protein encoded by FOXP2 appears to control coordination between mouth muscles and speech.

In 2001, it was connected to speech and language disorders and in 2002 its role in the development of spoken language was proven. The gene also enables mice to communicate by means of ultrasounds.

The new research tried to check if this could be applied in bats as well. Human speech seems simple when compared to the bat echolocation: the animal has to coordinate its nose, mouth, ears and larynx to produce and receive calls, while executing flight maneuvers guided by the returning ultrasounds, all in a matter of fractions of seconds.

The team sequenced the FOXP2 in 13 bats belonging to six families, some using echolocation and some not (only the fruit bats or flying foxes from the Old World do not use echolocation), but also in 23 other mammals, platypus (the most primitive living mammal) included, two birds and a reptile.

The bat's FOXP2 sequence had two times more changes than encountered in all the other species combined, pointing to a very rapid evolution. Closely related bat species, with similar ultrasonic skills presented similar amounts of changes, not common with more distantly related bats or flying foxes. Some bat species presented the same mutation connected to language disorders in humans.

"Our findings suggest that FOXP2 may have played a crucial role during the evolution and diversification of echolocation behavior in bats," said co-author geneticist Stephen Rossiter.

"The results back the idea that speech and language evolved from ancestral vocal and motor systems that became rearranged and more sophisticated through time." said Simon Fisher, a neurogeneticist at the University of Oxford, who found a link between FOXP2 variations and speech disorders.

Still, "to really make the case for a role of FOXP2 in echolocation, functional studies are necessary, such as knocking out the gene," said neurobiologist Constance Scharff of the Free University of Berlin.