Bats and dolphins, despite their distance on the evolutionary tree of life, both possess an uncommon ability among mammals: echolocation. Now, scientists have discovered that the similarities go down to the genetic level as well as the physical -- bats and dolphins independently underwent many of the same genetic changes that resulted in their special biological sonar systems.
Animals use echolocation to locate prey and navigate by emitting sounds, then listening for the echoes of those calls. Subtle differences in the echoes, caused by sound waves bouncing off of objects, allow animals to construct an image of the world around them. Bats and dolphins aren’t that closely related, but both developed the very specialized trait of echolocation independently; it’s a classic example of what scientists call “convergent evolution” (another example would be the physical similarities between bat wings and bird wings: analogous shapes, arrived at independently).
Researchers led by a team from Queen Mary University of London wondered if some of the genetic steps that bats and dolphins took on their separate evolutionary paths might have been similar. They compared at the complete genetic sequences of 22 different kinds of mammals, including both echolocating and nonecholocating bats, bottlenose dolphins, horses, dogs, mice and humans.
“Strong and significant support for convergence among bats and the bottlenose dolphin was seen in numerous genes linked to hearing or deafness, consistent with an involvement in echolocation,” the authors wrote in Nature. “Unexpectedly, we also found convergence in many genes linked to vision: the convergent signal of many sensory genes was robustly correlated with the strength of natural selection.”
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