Sensitive hearing may have evolved in mammal ancestors far earlier than scientists once believed. By modeling how sound moved through the skull of Thrinaxodon, a 250-million-year-old mammal predecessor, researchers found it likely used an early eardrum to hear airborne sounds. This challenges the long-held idea that these animals mainly “listened” through their jaws or bones. The results reveal that a key feature of modern mammal hearing was already taking shape deep in prehistory.
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