Researchers at King's College London have begun to uncover the cellular and molecular drivers underlying a key anatomical change during the evolution of mammals.
Non-mammals such as reptiles and birds have one tiny bone making up their middle ear, where we mammals have a chain of three. The extra bones are a repurposing of the non-mammal jaw joint, allowed by the evolution of a new mammalian jaw joint, known as the TMJ. This transition can be followed in the fossil record, and is reflected during embryonic development where the new parts of the middle ear develop connected to the jaw, with the ear and jaw separating when the TMJ is fully formed.
