Language is such an integral part of being human that it is not even learned. Instead, language develops naturally like an organ or what Steven Pinker calls the "language instinct." By the age of five years, humans know all the rules of language. Noam Chomsky named our automatic propensity for learning and mastering the complex and sometimes illogical rules of grammar, our "language acquisition device," and his theory was strengthened by his discovery of a "universal grammar" which is the common basis for all human languages.
It is very difficult to trace direct evidence for human speech and language evolution in the fossil record. None of the soft anatomical parts involved in speech—like the tongue, larynx (voice box), and soft palate—are preserved and the bony parts that do fossilize do not reveal very much useful anatomy.
There is still no conclusive evidence that any hominin other than modern humans had language or could even speak like us. The small, floating horseshoe-shaped bone in the neck called the hyoid was thought to hold some clues, and since it is preserved in the Kebara Neanderthal (from 60
Kya in Israel), hopes were high. But the anatomy of the bone, although humanlike and not at all chimpanzee-like, was found to be identical to a pig's, so it is not diagnostic for language abilities. Although, when the length of the neck and the base of the face and jaw are considered, the Neanderthal vocal tract appears to have ape-like proportions. Apes and human babies have a high larynx and they can suckle and breathe at the same time. But as humans develop past infancy, their larynx lowers and this is what helps us make a wide range of vowel sounds in the throat, but inhibits us from breathing and eating at once.
Because specific areas of the brain are linked to speech and language, there may be potential to glean evidence for language from brain en-docasts. For instance, that of a particular H. erectus cranium SM 3 (from Sambungmacan, Indonesia) has a pronounced Broca's cap, a bump on the left frontal lobe corresponding to Broca's Area, which is the anatomical region associated with speech production and language processing. But, Broca's caps can be found on chimpanzee endocasts so they are not foolproof indicators of language. Furthermore, the brain is wrapped in a covering of meninges, which is composed of the layers called pia mater, arachnoid, and dura mater, that dulls the brain's impression for an endocast, making interpreting the bumps on the brain an even more difficult task.
Complex coordination and control of the muscles of the trunk are necessary to control finely tuned breathing patterns during human speech. So it is possible to link the size of the spinal cord to the quantity of nerves required to monitor breathing and speech. The size of the hole through the vertebrae, the vertebral foramen, is small in H. erectus (based on the Nariokotome Boy), implying that his spinal cord was small too. Thus, there was probably not as much enervation of the thorax in H. erectus as in modern humans and it is unlikely that the Nariokotome boy could speak like us. But that does not rule out the possibility that he had a rudimentary language.
Because the anatomical evidence is inconclusive, we cannot rule out any particular hominin from having language. However, scientists have traditionally correlated symbols, art, and human culture and technology with the presence of language and none of that appears until after 100 Kya. However, cooperative hunting, with evidence of driving herds off cliffs by the middle Pleistocene, may be an earlier innovation that can be linked to language. The social complexity (and thus cognitive functioning, which is required for language) involved in cooperative hunting exists on a much larger scale than that accomplished by dogs and cats that hunt in groups.
The genetics of speech and language are beginning to unfold. Mutations in the gene FOXP2 cause a person to struggle with motor control of the mouth and facial muscles so that word pronunciation is difficult. Persons with mutations at the gene also have deficiencies in certain aspects of grammar and cognition. Once FOXP2 was identified, scientists searched for its function in normal humans and other animals. FOXP2 is a regulatory gene, shared in similar forms by all vertebrates, that manages the activities of other genes, some of which are involved in language but others are not involved in language at all (which complicates hypotheses for its selection based solely on language). The human version of the gene differs from the mouse by only three amino acids and from the chimpanzee by only two, but it is possible that these two changes were of functional significance to the origin of language. Molecular clocks of human FOXP2 point to a very recent origin within the past 200,000, but because it is a regulator gene it is highly unlikely that it would be the only gene involved in evolving language abilities. FOXP2 reminds us that evolution is "descent with modification" as Darwin said, because something so crucial to making humans "human" probably evolved from primitive genes that are not unique at all to humans.
Selection must have acted very strongly on language the way it acted on bipedalism. Hypotheses for its earliest advantages include the ability to hunt more effectively by exchanging information about the physical and ecological environment. Robin Dunbar suggests that language evolved in order to exchange information about the social environment, or basically to gossip. Social communication is no trivial matter, since information about who can be trusted—that is, who plays the reciprocity game fairly—can be shared across a community (see the section on "Altruism and the Human Colony" in this chapter). With language, an individual would not need to keep track of every single one of the complex social and political relationships and networks in their community. By gossiping, that information could be shared and remembered much more easily. Language in this sense allowed humans to live communally in large groups and ramped up the importance of an individual's reputation if others could make information about him or her public knowledge. Language could also have been, as Geoffrey Miller suggests, a seduction tool favored by sexual selection.
Primates rely heavily on both vocal and nonvocal language and foundations for complex human communication exist in primates. As a whole, the group uses its increased numbers of facial muscles to convey emotions. White-handed gibbons use specific songs for warning others that a predator is threateningly close. Chimpanzees are aware of the
Table 5.2 When Are Hominins Humans?
"Hominin" Teeth Bipedalism Small canines Leg proportions Stone tools Meat
Geographic dispersal Body proportions Fire
800 Kya 500 Kya 100 Kya 100 Kya?
6 Mya 5 Mya 5 Mya 3.2 Mya 2.5 Mya 2.5 Mya 2.5 Mya 1.8 Mya 1.8 Mya
Ardipithecus or earlier
Ardipithecus or earlier
Homo sapiens importance of facial communication and have been observed to literally wipe fear smiles off their own faces in the presence of an aggressive group member in order to appear unafraid. Captive chimpanzees will naturally develop specific calls for specific food items like bananas and wild chimpanzees use specific vocalizations for snakes and threatening strangers, and they also have hunting calls.
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