How some vertebrates evolved biological sonar

Sid Perkins in Science News:

4291Bats are members of one of the most diverse groups of mammals, and the echolocation capability that enables some bat species to detect, track, and catch insects on the wing—even ones as small as mosquitoes—is a crucial part of bats’ success.

Sonar use has evolved independently among widely disparate groups of creatures. For aquatic mammals, such as porpoises and whales, the sequence of adaptations that led to echolocation is well preserved in the fossil record of their ancestors. But no such trail exists for bats, a group whose oldest known remains indicate that echolocation was already in use.

In the handful of bird species that use sonar, the origin of that ability is even murkier. Some echolocating species have close relatives that apparently possess the anatomical means to echolocate but don’t use it, implying that avian echolocation is a behavior that some species simply haven’t learned. For insights into how echolocation evolved in birds and bats, scientists are turning to DNA, a modern source of information about ancient biological relationships.

More here.