In addition to Ameslan, chimpanzees and other nonhuman primates are being taught a variety of other gestural languages. And it is just this transition from tongue to hand that has permitted humans to regain the ability-lost, according to Josephus, since Eden-to communicate with the animals.
Carl Sagan, Dragons of Eden: Speculations on the Evolution of Human Intelligence
animal-communication, animal-intelligence, communication, sign-language