Imagine what a dinner conversation would be like if you had decent table manners, but the ears of a lizard. Not only would you have to stop eating whenever you wanted to speak, but, because parts of your ears are now attached to your jaw, you’d have to stop eating whenever you wanted to hear anybody else, as well. With no fork action on your end, your waiter would soon conclude that you were obviously “done working on that” and would whisk your unbreached baked ziti away.

Sometimes it’s the little things in life that make all the difference  in this case, the three littlest bones of the human body. Tucked in our auditory canal, just on the inner side of the eardrum, are the musically named malleus, incus and stapes, each minibone, each ossicle, about the size of a small freshwater pearl and jointly the basis of one of evolution’s greatest inventions, the mammalian middle ear. The middle ear gives us our sound bite, our capacity to masticate without being forced to turn a momentarily deaf ear to the world, as most other vertebrates are. Who can say whether we humans would have become so voraciously verbal if not for the practice our ancestors had of jawboning around the wildebeest spit.

The middle ear also explains why mammals, as a group, have the sharpest hearing on Earth and the greatest diversity of listening styles, from the bats and dolphins that can detect pressure waves bouncing around at the spiky, ultrasonic end of the bandwidth, to elephants and humpbacked whales that can hear infrasonically, capturing the long, low sound prints muttered by their peers for miles around. All told, a new study suggests, the middle ear was such a great invention, such an essential part of being a mammal, that once evolution had seized upon it, no crude substitute or older model would do.

In the current issue of the journal Science, paleontologists report on the fossilized remains of a newly discovered mammal from the Mesozoic era, some 123 million years ago. The snouty, 3-ounce, chipmunk-size animal, named Maotherium asiaticus, lived in what is now northeastern China and darted around the feet of the dominant dinosaur overlords, as mammals had been doing for some 100 million years.