Symbolic thought and language: purely human abilities?
Deliberate communication of one form or another undoubtedly started a long time ago in animals. Vocal speech is merely the most sophisticated form of animal communication, and has selected for a number of specialized physical changes in humans. Vocal speech has special advantages over simple gesture language apart from its ability to convey complex ideas. We can communicate in the dark, through trees, and without looking at the person we are speaking to. It is much easier to con, deceive, and tell lies, and to hide our communication from strangers speaking other tongues. Children learn to lie at around the age of four. Some have suggested that males’ prowess at telling jokes, and making females laugh, might have been an element in sexual selection. Like all other aspects of culture, however, language was invented and has to be internally reinvented in every child learning to speak.
We modern humans justifiably differentiate ourselves from our other living primate relatives by our power of speech. Unfortunately we do not leave the qualitative comparisons there. In the same way that we exaggerate religious and ethnic variations among our own kind, we try to take perceived differences from other apes much further in order to establish an us/them framework. A recent and extreme manifestation of this habit of exclusion between modern human groups was seen in the term untermensch (literally ‘under-people’ or ‘less-than-human’) used by the Nazis to describe the people they persecuted, robbed and murdered.
We have also credited ourselves with having multiple unique intellectual and manipulative skills that fence us off from the rest of the animal kingdom. Trying to look through that fence is condemned as ‘anthropomorphism’. In spite of this, since the beginning of the twentieth century our nearest living relative, the chimp, has surprised careful observers by charmingly picking the wicker from these hurdles one by one. Old myths of unique human skills have died hard. First, people maintained that humans were the only animals to use tools. When that idea lost credibility, the prejudice was refined to state that humans were the only animals to modify tools. When this was disproved, we had to content ourselves with the assertion that only humans were capable of inventing and making tools. Again, chimps proved us wrong.
Much of this simple information was available from Wolfgang Köhler’s studies in the early 1920s of a chimp colony on the island of Tenerife. Köhler, a Gestalt psychologist, went much further than showing that chimps could solve problems. He elegantly demonstrated that they were capable of both abstract and rational thought.24 Unfortunately, few humans were able to look at his experimental results rationally at the time. It took Jane Goodall and others with their patient observation and brilliant camera-work in the field to convert the scientists and the public to the implications of Köhler’s results, much later in the century.
The big surprise in the second half of the twentieth century was to find that chimps, a non-speaking ape species separated from us by at least 5 million years on the evolutionary tree, have a nascent language ability. Chimps have been taught to communicate with humans. More impressively, they are able to take their new skill and use it to communicate with one another using symbolic and coded signs. The greatest star of this story is Kanzi, a bonobo (bonobos are close relatives of chimpanzees, with several behavioural traits reminiscent of ourselves). Kanzi learnt to communicate using a complex coded symbol language on a computer. He also spontaneously learnt to comprehend spoken English, correctly interpreting syntax. The scale of his achievement could have something to do with the fact that he was a bonobo (it appears that bonobos may be slightly closer genetically to humans than other chimps) but it seems more likely the result of his having picked up the skills spontaneously as an infant at his chimp foster mother’s side, when his childlike learning ability window was open and at its best. She was actually the intended target of the language teaching and, as an adult, was struggling to learn these new symbols. Chimps have also been shown to demonstrate abstract, symbolic, and rational thought, as well as what is termed ‘symbolic inference’ and ‘symbolic manipulation’, although they are clearly not as good at these skills as we are. Most likely, this is simply a matter of degree. As far as language is concerned, chimps are obviously hampered by lack of vocal control and are either not disposed to or unable to see the value of extended non-verbal communication.25
Surprisingly, the full implications of these experiments are still largely ignored by linguists. To understand this obstinacy we have to appreciate the dichotomy in current theories of the origins of language and thought. Two lines of argument have run in parallel since the nineteenth century. The first of these, in which language is seen essentially as an invention, was initiated by the eighteenth-century Enlightenment philosophe Étienne Bonnot de Condillac. He argued that spoken language had developed out of gesture language (langage d’action) and that both were inventions arising initially from simple association. The Condillac view anticipated the concept of cultural evolution and, with some development, can be traced through Darwinism and a mid-twentieth-century thinker, Ronald Englefield, right down to the present day with the work of New Zealand psychologist Michael Corballis and others. The full theory sees gesture language as arising originally among apes, and then becoming conventional or coded as the new skill drove its own evolution. Subsequently, verbal signals, some already present in the ‘innate’ primate repertory, were co-opted and developed into deliberate coded communication. Evolutionary pressures then promoted the development of the vocal apparatus and also of part of the brain immediately next to that responsible for gestures. This speech centre is often called Broca’s area.26
Touched with the gift of speech?
The other, at present dominant view of the origin of language is almost creationist in its denial of the process of evolution. Language, in this case specifically the spoken word, is seen as having arisen suddenly among modern humans between 35,000 and 50,000 years ago as some kind of ‘big bang’ speciation event. According to Noam Chomsky, the ability to speak words and also to use syntax was recently genetically hard-wired into our brains in some kind of language organ. This view of language is associated with the old idea that logical or rational thought is somehow dependent on words. This concept originated with Plato and was much in vogue in the nineteenth century with writers such as Jakob Grimm – ‘Animals do not speak because they do not think’ – and Max Müller – ‘Language is our Rubicon, and no brute will dare to cross it’ and ‘without speech, no reason, without reason, no speech’.27
The creationist notion of a great leap forward in the quality of human thinking is further reflected in a common interpretation of Upper Palaeolithic art in Europe. European cave paintings and carved figurines which have been dated to over 30,000 years ago are seen, according to this perspective, as the first stirrings of symbolic and abstract thought and also of language. However, the mature sophistication of the earliest paintings found in Chauvet Cave in the south of France seems to deny this view.28 In any case, such a Eurocentric interpretation ignores the knowledge that Australians were already painting on rocks on the other side of the world at the same time as the early Europeans. It is absurd to suggest that they and the rest of the world had to learn their own speech and painting from Europeans. There is every reason and much evidence, as will be discussed in this book, to suppose that their common African ancestor had already mastered the skills of speech, art, and symbolic representation long before leaving Africa 80,000 years ago.
Another problem with the creationist or ‘big bang’ view of modern humans’ unique abilities is that there is evidence that Neanderthals had the same specialized vocal anatomy that we have. The possession of a similar hyoid bone, an enlarged thoracic spinal cord, and an enlarged orifice to carry the hypoglossal nerve to the tongue, are consistent with Neanderthals speaking. On Baldwin’s hypothesis, these attributes also indicate that Neanderthals’ (and our own) common ancestor Homo heidelbergensis was already speaking over half a million years ago. Since Homo he
idelbergensis also had an equally enlarged nerve orifice and some other key anatomical features of speech, the argument could possibly be stretched back further to Homo erectus, who shows evidence of a lopsided brain. The latter is thought to be an important associated phenomenon of language. Homo habilis is thought by some to show an impression, inside the skull, of Broca’s area, consistent with the view that the process of specialized enlargement to adapt to speech had already begun 2 million years ago.29
This anatomical speculation brings us back to the first humans and the dramatic sprint in brain enlargement in Homo and Paranthropus. If there ever was a big bang in the speciation of smart hominids, this was it. Tim Crow, a professor of psychiatry in Oxford, has argued that two important speciation events can be inferred from two closely related mutations on the Y chromosome, sometime after the split between chimps and ourselves. There is some reason for supposing that one or both of these mutations might be associated with cerebral asymmetry, and possibly with language. If so, then we might speculate that the first mutation occurred in the common ancestor of Homo and Paranthropus and the second in Homo erectus, since the latter shows the first evidence of cerebral asymmetry.30
Modern neurophysiological research, using a variety of techniques including active imaging, has further undermined the biologically deterministic view of thought and language evolution and acquisition. We now know that the syntax of different types of language is handled in different parts of the brain. Syntax is not hard-wired: it is inferred by young children, who, compared to adults learning a new language, have a greater and more flexible ability to decode symbolic associations and guess the correct syntactic inference. Humans are not unique in having a critical period in development when language skills are acquired. The same phenomenon is seen in the ‘singing’ non-primates, such as birds and whales. The complex, often unique songs sung in later life by these animals are learnt, modified, and imprinted at an early stage. Moreover, research shows that speech is not necessarily limited to a particular part or parts of the brain.31
These neurophysiological studies have suggested an alternative to the Chomskian theory of language evolution, one which incorporates the ideas of Condillac, Englefield, and Corballis. This is the view that spoken language was ultimately a primate invention, like toolmaking, which drove the biological evolution of the brain and vocal apparatus. As a cultural invention, it has also evolved separately outside our bodies within specific cultural communities. The unique combination of lexical and syntactic features of a language such as French are the cultural possessions of the French community, and clearly do not result from a unique biological aspect of being French. Each language and its syntax evolves from one generation to the next, constantly adapting itself to cope with the learning biases of each new set of young immature minds.
In summary, of all the mental and practical skills that philosophers have put forward as qualitative differences between modern humans and chimps, the only one that remains is human speech. Clearly, there is a great quantitative difference in intellectual ability, but human intellect did not suddenly flower 35,000 years ago in the European Upper Palaeolithic – it had been evolving over the previous 4 million years. For the past 2 million years humans have been improving on the walking-ape model by using their brains, but they may have been aided in this by speech-driven coevolution in brain size. Just like the flexible new trunk of the Elephant’s Child in Kipling’s fable, the enhanced abilities of our new brain to manipulate symbolic concepts and sets has been turned to a variety of complex tasks other than speech. The fact that we can speculate about the geometry of the universe and its origins, and even start to explore it, suggests that our intellect has few limits of flexibility and fresh application.
We have seen that the cycles of African desiccation accompanying ice ages encouraged the growth of human brains over 2 million years ago. This also happened in our sister genus Paranthropus, but not in large savannah-dwelling monkeys, suggesting that some special behaviour which depended on brain size was already being shared exclusively by those hominids. There is a tendency to see runaway brain growth as a recent event among humans, but if we look at the evidence we find that the opposite seems to be true. The most rapid proportional brain growth happened between 1 and 2 million years ago. By the time modern humans came along, brain growth had largely slowed down. The paradox is that our apparent behavioural explosion is mostly recent and is accelerating geometrically.
Rather than accept the obvious – that human culture feeds into itself, thus generating its own accelerating tempo – many anthropologists, archaeologists, and linguists believe that something ‘genetic’ happened to the way our brains worked within the last 100,000 years, producing a different kind of human brain with new wiring. Some go even further, suggesting that language is the most obvious candidate for that new and unique behaviour.32 Frankly, I think this is perverse logic and un-Darwinian. Deliberate coded communication, or ‘language’, is certainly a useful, new, and unique behaviour. How much simpler, though, if this was what had differentiated our early ancestors from other large savannah primates and had driven evolution of their brain size 2.5 million years earlier so that they could communicate better and cope with their worsening environment in a more inventive way.
So far I have made little reference to genetics, which is going to figure prominently in this book. Much of the human history of the past 2.5 million years has been reconstructed by a combination of studies of fossil bones and past climates. All but one human species became extinct, some of them long ago, so we do not have their living genes to study. This is not to say that genetics has nothing to tell us about the dark ages of our evolution, before modern humans appeared on the stage. In the 1970s, some geneticists began to use crude immunological tools to measure protein similarities between species, and suggested that humans and chimps were even more closely related than had been thought. Their suggestion was met with derision at the time, but as techniques of comparison turned from immunology to demonstrating a basic genetic similarity and then eventually to measuring precise genetic differences, they were vindicated. The realization has grown that we are much closer to chimps than to the other great apes, the gorillas and orang-utans, our common lineage having split not much more than 5 million years ago.33
To say that there are no genes left over from past human species is also not quite true. Most of our nuclear genes are inherited nearly intact from ancestral humans and apes. Some human genes can be found in several forms that split from one another long before we appeared on Earth. Scientists have also extracted short fragmentary stretches of mitochondrial DNA from a number of Neanderthal bones, and are now in a position to answer basic questions about how closely we are related to them and whether there are any of their genes left in modern human populations.
However, the real revolution in understanding human genetic prehistory covers the last 200,000 years, which is what concerns us here. For this period, the new genetics has shone a bright light onto a contentious field previously dominated by collections of European and African stone tools and a few poorly dated skeletal remains. Before turning to details of genetic tracking, it may help to look at some of the ideas behind genetic inheritance and how they have evolved. The concepts are mainly simple, being related to our own everyday understanding of and pre-occupation with inheritance, but are often misrepresented, either for reasons of hype or because they are veiled in jargon.
The secrets of the peas
Humans have been aware of some idea of genetic inheritance ever since the first animals and plants were domesticated. Farmers made deliberate attempts to breed out unwanted features such as large size or aggression. Cereal grain was bred for increased size and ease of cropping. However, much of the detail of ‘farmer’s lore’ was fundamentally wrong, though crudely functional. Speculation about the exact mechanisms and rules underlying inheritance increased in the mid-nineteenth century with the publication of Charles Darwin’s Origin of Species, but Darw
in’s understanding of the principles of heredity was not much more sophisticated than that of his predecessors. Instead it was his contemporary, the nineteenth-century Austrian cleric Gregor Mendel, who first laid down a logical framework for understanding how parental characteristics were transmitted, based on his obsessive mathematical calculations on the inheritance of the colour and shape of pea plants.
Basically, Mendel showed that, for any particular physical feature, or character, such as flower colour, each pea plant possessed two genes (although he used another term) that determined the expression or outcome of the character. Variation in relative dominance between these two genes determined their expression in the plant. During the process of sexual procreation, only one of these genes would be donated by each parent to each offspring plant. Thus, each offspring inherited a mixture of characters from each parent, with the combined effect of two genes determining each physical character at each generation. Since either parent could have different functioning gene types, for instance different petal colours, for each (and any) pair of genes, and only one of the two was chosen at random, the proportions of different varieties of offspring formed a pattern that could be predicted from a knowledge of the characters possessed by each parent. In this way, Mendel showed that inheritance of characters took place by the transfer of discrete packets of information. The variation in the offspring was down to the precise but random mix of these packets, or genes, in each individual, whether it be a pea seed or a human.
Out of Eden: The Peopling of the World Page 5