India, March 7 -- The outer ears that sit on the sides of your head share an unexpected genetic heritage with the gills of fish. According to research published in the journal Nature by scientists from the University of Southern California, the genes that provide the instructions for human ears once directed the formation of gills in our ancient aquatic ancestors, giving us a new and incredible example of genetic recycling.

"When we started the project, the evolutionary origin of the outer ear was a complete black box," said Gage Crump, professor of stem cell biology and regenerative medicine at the Keck School of Medicine of USC and senior author of the study.

Because elastic cartilage which makes up the outer ear rarely fossilises, th...