Seals have a unique superpower in their ears, and we finally know how it evolved

Seals are the only mammals that hear equally well in air and water. Scientists have finally figured out how. The Conversation reports that specialized tissue in seal ears—packed with blood vessels—fills with blood during dives. Since blood has roughly the same density as water, it can channel underwater sounds to the inner ear with virtually no loss. Early seal ancestors couldn't do this; they heard in air only. About twenty-six million years ago, when seals moved into the ocean, they started evolving this amphibious hearing. Over the next several million years, true seals refined the ability, developing acute underwater hearing while keeping their land-based ears sharp. Now, as ocean noise pollution grows, that sophisticated dual hearing is increasingly threatened.

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