A major difference between mammals and our reptile ancestors is the presence of our complex, highly sensitive ears.
Researchers from the University of New England (UNE) and the University of Queensland want to shed light on the evolution of this differing feature, challenging current beliefs which are ‘based on insufficient data’.
“What is clear is that over tens of millions of years – bones that once formed part of the reptilian jaw were greatly downsized, repositioned and repurposed to help conduct sound more effectively to the inner ear in mammals,” said co-author and director of UNE’s Function, Evolution and Anatomy Research lab, Associate Professor Stephen Wroe.
“One explanation has been that these bones were pushed away as the mammalian brain expanded. It has also been widely thought that the evolutionary process, which is now well-documented in the fossil record, is quite tightly recapitulated during the development of living mammals.
“In some mammals, the process whereby bones in the embryo’s jaw shrink and move to become part of the ear is relatively easy to track. This makes them a great test case for examining theories on the jaw transition.”
Using high resolution CAT scan data of Australian marsupial embryos the research team showed that there was no support for the notion that the process was driven by an expanding brain. It was also clear that the process documented in the fossil record is perhaps not so perfectly recreated in the development of living animals.
Read more here: University of New England & The University of Queensland.