Seals Evolved Amphibious Hearing 26 Million Years Ago Using Ear Tissue
Updated
Updated · The Conversation · Jul 14
Seals Evolved Amphibious Hearing 26 Million Years Ago Using Ear Tissue
3 articles · Updated · The Conversation · Jul 14
Summary
3D scans of seal ears found cavernous, blood-filled tissue that lets underwater sound reach the middle ear with less than 1% signal loss, versus 99% if the ear remained air-filled.
Statistical comparisons of modern carnivorans and fossil relatives showed the earliest seal ancestors heard only in air, while marine seals such as Enaliarctos had evolved amphibious hearing by 26 million years ago.
Those early marine seals initially heard less well in both air and water, before later seal lineages developed modified middle ears that restored acute hearing in both environments and made true seals especially sensitive underwater.
The findings help explain a rare mammalian ability that now faces a modern threat, as growing ocean noise from ships, construction and sonar can mask communication and damage hearing in seals and other marine mammals.