Did our outer ears come from ancient fish gills?

Human outer ears may have evolved from the gills of prehistoric fish. Gene-editing experiments indicate that cartilage in fish gills migrated into the ear canal millions of years ago during the course of our evolution.

- SASCHA PARE

Going even further back, our outer ears may have evolutionary roots in ancient marine invertebrates, such as horseshoe crabs. The new research sheds light on the mysterious origins of outer ears, which are unique to mammals. “When we started the project, the evolutionary origin of the outer ear was a complete black box,” said Gage Crump, a professor of stem cell biology and regenerative medicine at the University of Southern California.

Researchers already knew that our middle ears, each of which sits behind the eardrum and comprises three small bones, arose from the jawbones of ancient fish. This example of evolution transforming and repurposing anatomical structures “made us wonder whether the cartilaginous outer ear may also have arisen from some ancestral fish structure,” Crump said. Our outer ears and those of other mammals are made of a subtype of cartilage called elastic cartilage.