New fossil found in China reveals evolution of hearing skills in mammals

According to a study published on Thursday in America's magazine Science, the long-sought fossil evidence of the first step in this epochal evolutionary pathway has been found. The researchers say that the discovery has filled a missing link in the evolution of mammals’ auditory arrangement. Scientists have discovered it as a big step in their ideas and concepts and the material basis on which they can discuss the very intricate evolutionary processes.

Discovery of six specimens

Excavation of a 123-million-year-old igneous rock formation has lead to the discovery of fossils of six specimens of a previously unknown species called Origolestes lii in northeastern China. The creature is an ancestor to therian mammals. Using high-resolution CT scans and other imaging techniques, the Chinese-led team of researchers were able to describe the specimens in detail, including the details of the structure of their auditory bones and cartilage, which unlike the earlier species lacked the bone-on-bone contact.

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The tiniest three bones collectively known as the “ossicles” in the middle ear transmit vibrations from the eardrum to the cochlea, significantly sharpening your hearing. These auditory ossicles are unique to mammals. Reptiles and birds all have only one middle-ear bone which is fused with the joints of their jaw. The ossicles are an important evolutionary innovation despite their size. 

They emerged independently multiple times in mammals, not only because of the resulting boost to hearing but also because of their detachment from the jaw freed those animals to adapt to a wider variety of food sources. Scientists have hypothesized that the decoupling of the hearing and chewing system removed the physical constraints the two processes placed on each other which lead to an improvement in their hearing as well as a diversification of the food they ate. Guillermo Rougier, an evolutionary biologist at the University of Louisville who is not associated with the research said that it's a fantastic set of evidence. The discovered fossils were a treasure trove for researchers. And an embarrassment of riches, truly.

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