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Chapter II. Evolution of the Human Mind >> Development of the speech apparatus

Development of the speech apparatus

Speech provides a method of communication superior to sign communication. Group members using sound do not need to see the speaker in order to receive a warning. Auditory warnings are often used in communications between non-human primates in the wild. Recall that the vervet monkeys of East Africa have different warnings for different threats (a leopard, a snake, an eagle, and a baboon warning), and so we can say that they have words for these predators. They have words for objects stored in their memory. Vervet monkeys do not have words for eyes, ears, palms, and tails, since they have no use for these words. Their visual system is not accustomed to dissecting visual objects into such fine details and matching these details directly to memory. Therefore their visual system is not trained to generate mental images of an eye, an ear, a palm, or a tail. Words are only good for communicating information that a listener can understand. Since monkey listeners are not able to generate a mental image of an eye, an ear, a palm, or a tail, the monkeys’ language lacks these words.

Since apes do not identify many elements in the visual field, there is no evolutionary pressure on the vocal apparatus. Monkeys, chimps, and gorillas have a vocal apparatus that perfectly suits their particular needs. It is likely that the physical ability of the vocal apparatus to generate sounds follows the need of any particular animal. In fact, the vocal apparatus in birds evolved independently from mammals. Many singing birds use sounds for courtship, alarms, and to keep members of a flock in contact. Some birds, including African Grey Parrots and Indian Mynah birds developed the ability to mimic a wide range of sounds (including human sounds). In the wild it allows them to imitate other species of birds and animals. The point is that, evolutionary acquisition of a better vocal apparatus is not such a big deal. When an animal benefits from making a wider range of sounds, it acquires a better vocal apparatus. In the case of hominids, redesign of the vocal apparatus was particularly simple. The larynx and the hyoid bone had to change their positions by descending down along the trachea. In fact, the hyoid bone of the human neonate is positioned as high as in other mammals. In both human and chimpanzee larynxes descend during postnatal development (Nishimura, 2003). However, the human larynx descends significantly lower than that of the chimpanzee, allowing humans to produce a wide range of sounds that other animals cannot produce. Thus, the only needed evolutionary adjustment was that of extending time the larynx is allowed to descent during child development.

The evolution of hominids from Homo habilis (2.4 million years ago) to Homo sapiens (150,000 years ago) involved a greater propensity to separate a whole image into its elements. As hominids were able to separate more and more elements from the visual image, they needed more and more words to describe these elements. This put a pressure on the development of more sophisticated vocal capabilities in order to describe the elements. Hominids needed words for all the elements that were important to them. Do we find support for this idea in the skeletal remains? Yes. We observe a consistent improvement of the speech apparatus from a primitive one in Turkana boy (Homo ergaster) to the Neanderthal, who was probably capable of generating child like sounds, to modern humans capable of generating complex sounds. The evolution of the vocal apparatus just followed the hominid’s needs for communication.

A conversation with a Neanderthal

It is likely that Neanderthals had hundreds of words in their vocabulary (just like chimps are able to learn hundreds of signs). They had names for all the elements that were important to them such as handaxe, spear, spearhead, meat, and bone. They had words for many feelings such as excitement, fear, and pain. They had multiple auditory warnings. They could probably compare two objects, so they may have had words such as “smaller”, “bigger”, “shorter”, and “wider”. However, the Neanderthal language was a non-synthesizing language: it was still a language of codes. A Neanderthal who learned the words for a cup and a keyboard would not be able to synthesize a new mental image of “a cup on top of a keyboard”. A Neanderthal who learned the words “fish”, “eat”, and “human”, would not see a difference between the phrases “human eats fish” and “fish eats human”. One needs to be able to synthesize a mental image to understand complex syntax. Neanderthals could not synthesize a new mental image and therefore they would not have had a need for a synthesizing language. Neanderthals could not verbally describe toolmaking. Neanderthals and all the hominids before Neanderthals would have to demonstrate toolmaking in a hands-on presentation.

What kind of conversation could you have with a Neanderthal? The conversation could be similar in content to the one you could have with a two-year-old child or a talking ape (like Koko). You could teach a Neanderthal to say some words in English, since Neanderthals had a developed vocal apparatus. A Neanderthal could explain to you what he wants (an apple, a banana, or a piece of meat), he could express his feelings, he could ask you to bring something, etc. However, a Neanderthal could not explain to you a complex concept that required mental synthesis on his part. A Neanderthal could have shown you how to make a spear, but he could not have explained the process in a speech at a lecture hall.