a . Mark P. Cosgrove, The Amazing Body Human (Grand Rapids: Baker Book House, 1987), pp. 106–109.
“If we are honest, we will face the facts and admit that we can find no evolutionary development to explain our unique speech center [in the human brain].” Ibid., p. 164.
b . Jeffrey T. Laitman, “The Anatomy of Human Speech,” Natural History, Vol. 93, August 1984, pp. 20 – 26.
u “Chimpanzees communicate with each other by making vocal sounds just as most mammals do, but they don’t have the capacity for true language, either verbally or by using signs and symbols. ... Therefore, the speech sound production ability of a chimpanzee vocal tract is extremely limited, because it lacks the ability to produce the segmental contrast of consonants and vowels in a series. ... I conclude that all of the foregoing basic structural and functional deficiencies of the chimpanzee vocal tract, which interfere or limit the production of speech sounds, also pertain to all of the other nonhuman primates.” Edmund S. Crelin, The Human Vocal Tract (New York: Vantage Press, 1987), p. 83.