Human Evolution

Dr. Philip Lieberman of Brown University explained on NPR's "The Human Edge" that [blank] humans diverged from an early-ape ancestor more than 100,000 years ago, the shape of the mouth and vocal tract changed, with the tongue and larynx, or voice box, moving further down the track. The tongue became more [blank] and independent and was able to be controlled more precisely. The tongue is attached to the hyoid bone, which is not attached to any other bones in the body. Meanwhile, the human neck grew longer to accommodate the tongue and larynx, and the human mouth grew smaller. The larynx is lower in the throats of humans [blank] it is in chimpanzees, which, along with the increased flexibility of the mouth, tongue, and lips, is what enables humans to speak as well as to change [blank] and sing. The ability to speak and develop language was an enormous advantage for humans. The disadvantage of this [blank] development is that this flexibility comes with an increased risk of food going down the wrong track and causing choking.