A Review of “Eve Spoke: Human Language and Human Evolution,” by Philip Lieberman

The following is a description of the text titled “Eve Spoke: Human Langage and Human Evolution,” written by Philip Lieberman, published in 1998. Lieberman is an experienced anthropologist who has worked with a talented array of researchers and at various prestigious institutions. This particular title covers a wide range of topics pertaining to both physical and cultural anthropology, as well as biology and anatomy. Knowledge and techniques from several different subfields are utilized to reach the conclusions posited by the author.

The main focus of the text lies with the origin of human language, including the biological aspects such as the mechanisms of speech, as well as the psychological and neurological factors involved in the evolution of language. To find support for his hypotheses he explores the evolutionary processes that made humans distinct from other species, particularly the cognitive and communicative abilities that differentiate Homo sapiens from any other species. A continuous theme throughout the book is the evolutionary relationship between motor skills, speech, language and cognition, forming a self-reinforcing progression towards the precise manual control and linguistic skills seen in humans today.

As a prerequisite for reading this text, it should be noted that the author Lieberman accepts the Recent African Origin(Out-of-Africa) model as the correct model of human migrations. According the Lieberman, the multiregional model of human migration does not account for the remarkable lack of genetic diversity among living humans. He also states that gene flow is an unsatisfactory explanation for this fact since gene flow would tend to eliminate regional variation, which is certainly not the case. As evidence for the improbability of the multiregional model, the author cites the research of William W. Howells, working at the Peabody Museum of A. and E. of Harvard University, who has studied the skulls of human populations worldwide. Howells has demonstrated that certain anatomical features of human skulls never occur in Neanderthal skulls, and the reverse is also true. The author’s son Daniel Lieberman, also an anthropologist, has cited a lack of physical features which would link H. erectus fossils directly with the present populations inhabiting the same places.

Lieberman also dismisses the concepts put forth by influential linguist Noam Chomsky, specifically the idea of a “language organ”. According the Chomsky, human infants are born with an innate “universal grammar”, which endows the infant with a complete knowledge of all the rules of syntax of all human languages. Once a child comes into contact with a spoken language, only the set of rules pertaining to that particular language are applied. Lieberman counters based on research by the University of North Carolina’s Gilbert Gottlieb, who found through experimentation with ducks that this principal does hold true for lower lifeforms. However since most human behavior, including many aspects of language, are learned, Chomsky’s theory cannot truly account for the child’s ability to effortlessly learn one or more languages before they are even five years of age.

Lieberman makes an attempt to summarize the history of the study of language origins starting with the first attempts to train chimpanzees to speak, in the 17th century. None have been very successful, and the author points out that this fact is due to humanity’s specialized anatomy and a special-purpose neurological “functional language system”, which regulates aspects of speech from the brain. He also describes the work of Jane Goodall, the foremost name in the study of chimpanzees. Her studies of chimps have done away with the notion that humans are special because they manufacture tools, and also disagree with the idea that tool-making was the key to the evolution of the human brain. Lieberman cites Goodall’s documentation of chimpanzees using tools, such as the familiar termite stick. The author notes importantly that different populations of chimpanzees use different tools which may never be adopted or conceived of by a distant population. This fact inherently reflects that chimpanzees have culture, and can also anticipate and plan ahead for tasks using tools.

Later, Lieberman details his work at Haskins Laboratories in New York. It is here that the author delves into studies of the morphology of primate skulls and airways. A very important observation made by Lieberman and his colleagues was the fact that the vocal tracts of human infants were more similar to adult apes and monkeys than they were to adult humans. The scientists also studied the Neanderthal skull unearthed at La Chapelle-aux-Saints in France. This skull’s lower section too showed a striking resemblance to that of a newborn human, particularly in the areas where the tissues of the airway attach to the skeleton. This perculiarity would become an important basis of Lieberman’s theories. Lieberman wished to explore the primate vocal tract, along with his colleague Ed Crelin, chief of anatomy at Yale University School of Medicine. They quickly found the difficulty of obtaining infant cadavers for research. This led the researchers into studying photographs of X-rays, particularly of the supralaryngeal vocal tracts(SVTs). The SVT contains the entire airway, including the mouth, from the larynx up or forward, depending on the species discussed. Eventually, Lieberman and Crelin moved on to fabricating molds and casts of this structure from silicone rubber, and made an important discovery.

One of the main pieces of evidence supporting Lieberman’s theory is the fact that the larynx and pharynx of the adult human is positioned differently from that of any other mammal, including newborn humans. The pharynx of apes, monkeys, dogs and human infants is positioned almost directly behind the larynx. In this position, the larynx is able to pull up into the opening to the nose, and allows food and liquid to pass down into the pharynx, with reduced possibility of ingested material entering the larynx, which would cause choking. This also allows for simultaneous breathing and suckling. In all other mammals, this morphological pattern remains unchanged throughout life, but in humans the structures begin to migrate within the body to a new position after about 3 months of age. At that age the larynx begins to drop down into the pharynx. By the age of 15, the larynx and pharynx have reached their adult configuration and size. The unique positioning of the larynx means that adult humans are much more susceptible to choking since food and liquid must pass over the larynx before entering the pharynx and on to the esophagus. The constricted and angled nature of the adult SVT leads to the conclusion that less space is needed to house these structures, which is indeed the case when compared to apes and archaic humans. This in turn leads to less space for the teeth, which can lead to impacted molars(wisdom teeth), which in pre-industrial humans could be fatal. The overall line of reasoning is that the shape, proportion, and configuration of the adult human supralaryngeal vocal tract is adaptive for nothing but the purpose of speaking. For breathing, eating and dental health, it is maladaptive.

Lieberman’s second major posit has to do with the origin of the neuroanatomical structures regulating speech. Lieberman bucks the traditional view that the area of the brain known as Broca’s area(along with Wernicke’s area) is the anatomical “seat” of language. Neurologist Paul Broca had reached this conclusion based on studies of a partially paralyzed patient with cognitive difficulties, who had previously suffered a massive stroke. The author cites Ralph Holloway of Columbia University, who states that there is no evidence that Broca’s and Wernicke’s areas were expanded or more developed in the genus Homo. Lieberman eventually conducted his own studies of brain mechanisms along with Dr. Chu-Yu Tseng at the Academia Sinica in Taiwan. Their studies focused on the speech deficiencies of patients with a brain disorder known as Broca’s aphasia. The illness results from damage to Broca’s area. A common symptom of aphasia is the inability of the patient to distinctly pronounce stop consonants. A patient’s [b] will often be heard as [p], [k] as [g], and so on. This lead to the conclusion that some defect was interfering with the timing of the patients pronunciation – the vocal cords were not activating at the correct time during speech. The similarity of these symptoms to those suffered in Parkinson’s disease led the team to the brain’s basal ganglia structures, which form circuits that connect different parts of the brain for various activities, and are known to be damaged in Parkinson’s sufferers. When the patients were given the drug L-dopa, which temporarily restores basal ganglia function, the patients were for a short time “cured” of their speech deficiencies.

This experiment led Lieberman to the conclusion that the neuroanatomical basis of speech and language is spread throughout the brain, and that language and speaking are complex processes which require input from various brain structures. Lieberman describes scientific examination of the brain using special chemical compounds known as “tracers”, which can spread through neurological pathways in the brain, highlighting circuits of neurons. Because the subject of experimentation dies during the process, this technique cannot be used on humans. However, important discoveries have been made using animal subjects. According to the research, different structures of the brain’s neocortex are linked to subcortical structures through independent networks of neurons which in the text are called neural circuits. The basal ganglia seem to perform an important role in receiving and forwarding signals through circuits. When the basal ganglia do not function correctly, as due to a reduced level of dopamine, the patient will suffer both cognitive and motor deficits, including speech problems. The overall theme is that the physical structures underlying speech involve many aspects of brain anatomy, and are very closely related to general cognition and precise motor controls.

Much of the text is focused on the linguistic abilities of archaic Homo, in particular H. neanderthalis. Along with Dennis Klatt, the author returned to the study of Neanderthal SVTs, from which they formed a computer program that simulates the Neanderthal vocal tract based on the fossils available, and X-rays of living humans speaking. After testing the procedure against previous acoustic analyses, the scientist began analysis of the possible sounds that could be uttered by Neanderthals. Surprisingly, they discovered that the Neanderthal SVT could produce virtually every human vowel except [i], [u], and [a]. These vowels also happen to be the “universal” vowels, since some form is found in every known language. Also, the Neanderthal speech would have had a nasal quality quite dissimilar to humans. Gordon Peterson, of Bell Telephone Laboratories, had conducted research while developing devices which could recognize human speech. One of his experiment’s involved having listeners write down the words they believe they had heard spoken by anonymous speakers. When the results were tallied, the vowel sounds [i] and [u] had been heard correctly nearly 100% of the time. These happen to be the vowels that Neanderthals were incapable of producing. Other vowels sounds, such as [e] had much higher error rates.

The importance of these experiments comes into view when combined with other scientific discoveries. First, since these universal vowels are less likely to be confused, they are more likely to be heard correctly over long distances or through loud background noise. This allows more precise communication, quicker reaction time for the listener, and lowers the chance of the speaker receiving the incorrect response from the listener. Obviously, humans who lived in proximity and concurrently with Neanderthals would have held this slight advantage over them. Better communication of any type would have given H. sapiens greater biological fitness than H. neanderthalis. Ezra Zubrow, of the State University of New York at Buffalo, shows that even a slight advantage of 1% in competition would have allowed humans to outcompete Neanderthals within 30,000 years. This conclusion also implies that Neanderthals and humans were genetically isolated. Lieberman supports this theory of genetic isolation, and cites the work of Guido Barbujani and Robert Sokal at SUNY-Stony Brook. Their studies compared the distribution of biologically “neutral” alleles in Europe to physical and linguistic maps. Areas separated by physical boundaries, such as the Alps or Baltic Sea were to be expected. But the researchers also found sharp genetic boundaries along lines that separated languages without the presence of physical barriers, such as Low and High German. The research led to the conclusion that language can also be a genetic isolating mechanism.

This leads Lieberman back to the Neanderthals. Since they would have been unable to produce important human sounds, they would have been incomprehensible and therefore highly unlikely to interbreed with anatomically modern humans – which is of course why they went extinct. Overall however, Lieberman does agree that Neanderthals were capable of speech as well as symbolic thought, more advanced than earlier members of Homo. Lieberman also states that it is likely that both H. habilis and H. erectus were able to communicate verbally, though not nearly to the degree that modern humans have done since about 150,000 years ago.

In closing, the author states the premise that language capabilities evolved along with precise motor control due to these characteristic behaviors being housed in the same areas of the brain. As the human ability to affect it’s environment developed, so did the human ability to describe it’s environment. Since the physical structures that allow us to speak are not adaptive for any other purpose, being able to talk must have been a highly adaptive trait.

The author Lieberman has an efficient, yet comprehensive view on the origin of language. This writing and the arguments within do have some weaknesses, however. At some points, he seems to just gloss over what he has built up as highly important research. Also, Lieberman seems prematurely dismissive of several posited hypotheses from other researchers. He seems to have a particular distaste for Noam Chomsky and his school. Some of the arguments he put forward regarding ape behavior were presented with little evidence, but the reader is advised to accept them as fact. The author makes a radical claim regarding Middle Paleolithic tool-making – that the tools were so difficult to make that H. erectus possibly had “skilled specialists” to make them. This statement flies in the face of much that has been established regarding hominid origins and culture. Also, the author practices some ethnocentrism when he continuously links the Holy Land with the origin of anatomically modern humans. He cites the Skhul V fossil as the oldest known modern human fossil, completely discounting older fossils found in Africa. He also adds a radical claim when he states the possibility that Mitochondrial Eve and Y-chromosomal Adam lived in the Levant. Overall however, this text was very informative and gives a more clear picture of the context within which human language evolved.