|Image by Bogdanov of Wikipedia|
Based on Japanese research, the argument is now settled... the ear evolved independently into a similar appearing eardrum, a phenomenon called convergent evolution.
How did they make this determination?
As we have already known, the ear in mammals (i.e. humans) develop from the lower jaw. What was unclear is whether this was also true in reptiles. If there was a common ancestor, the ear would also be found to develop from the lower jaw in reptiles. If the ear does not, that would imply convergent evolution.
So what the scientists did was inhibit the lower jaw formation in fetal mice and chickens.
As expected, no ear structures developed in mice lacking a lower jaw.
But in chickens, although no lower jaw developed, what happened was that TWO upper jaws from which TWO sets of eardrums appeared.
How cool is that?
Developmental genetic bases behind the independent origin of the tympanic membrane in mammals and diapsids. Nature Communications 6, Article number: 6853 doi:10.1038/ncomms7853