Another characteristic of modern humans is their parabolic dental arcade. The evolution of human dentition has many causes and effects and dentition is important to fossil classification. Homo species’ teeth shrank relative to their overall body size. Its canines in particular became smaller, which is important because this meant that Homo males no longer needed the larger teeth of other primates in order to fight for mating rights.
As the human dental arcade became more parabolic in shape, their faces came to possess more space for the articulation of different consonants and greater resonance for vowels, making a larger array of sounds available for human speech.
In order to summarise the output of human evolution in relation to other primates and to better understand the fossil record, a review of the primate phylogenetic tree on page 24 above is important.
Figure 4: The hominin family tree
Taking discoveries in order of the age of the fossils found, the first ‘node’ in the primate tree that links to humans (and chimps) is quite possibly Sahelanthropus tchadensis, literally Man of Chad of the Sahel area (‘sahel’ being cognate with Sahara, which gives name to what is today the largest desert on earth). Sahelanthropus is a potential direct link between humans and chimps but the more likely hypothesis is that it, like Orrorin tugenensis and Ardipithecus, was one of the first hominins as in the lower right portion of Figure 4. The repetition of the names above and below the split indicates the two major hypotheses regarding these hominin fossils. It lived some 7 million years ago. Though we have only parts of the cranium, mandibles and teeth of Sahelanthropus, it is important to the fossil record of the evolution of Homo sapiens because it represents several distinct but equally important possible clues to human evolution. It could even be the ‘node’ in the phylogenetic tree from which chimpanzees and humans split (Figure 4).
Before concluding the discussion of the rise of hominins, it would be useful to compare what is emerging about the cognitive and communicational abilities of other great apes in order to more effectively reflect on the nature of the different evolutionary paths – if any – to language.
Mammals are the most intelligent creatures of the animal kingdom. Primates are the most intelligent mammals and humans are the most intelligent primates. Therefore, humans are the most intelligent animals. This may not be saying much. After all, our intelligence is the reason we murder one another and fight wars. Our brains are a mixed blessing. Jellyfish get along quite nicely without brains.
Nevertheless, human language is possible only because of this greater intelligence. Humans are the only creatures known that use symbols and cooperate to communicate more effectively. And unlike other animals, when humans communicate they almost never say all that they think, leaving their hearer to infer meaning.
There are some prerequisites, or what are often called ‘platforms’, needed for language.3 Two of those are culture and ‘theory of mind’ – an awareness that all people share cognitive abilities. Culture is an important topic, but right now it is worth discussing the theory of mind, because this also helps gauge an area of cognition where humans are regularly claimed to have something that no other animal has – the ability to ‘read’ the minds of others. Although actually being able to see or hear the thoughts of others is science fiction, there is some truth to the idea that humans can guess what others are thinking and then use this knowledge as a key to communication.
To cognitive scientists such as Robert Lurz, mind-reading is ‘the ability to attribute mental states, such as beliefs, intentions and perceptual experiences, to others by the decidedly mundane and indirect means of observing their behaviours within environmental contexts’.4 An example of this might be to see a man with two bags of groceries standing outside the entrance to a house feeling around with his free hand in his pockets. A person with a knowledge of locks and keys and the custom of locking one’s house should be able to guess that the person is searching for his keys and that he plans to unlock and then enter the house. Even for this seemingly simple scenario, there is a huge amount of cultural knowledge being drawn from. Amazonians who lack locks and keys might not have a clue as to what the man has his hands in his pockets for. And yet all humans will most likely recognise that the man has an intent, a purpose or a goal; that his actions are not random. That’s because all humans have very similar brains, which is in essence what the theory of mind is. Folks with autistic spectrum disorder might not understand this, because there is reason to believe that some forms of this set of ailments are caused by a lack of this kind of awareness.
Language works only because people believe other people think enough like they do to understand what they want to tell them. When one says what one is thinking, they do so believing that their hearer will be able to understand, infer conclusions about and match our words to their own experiences. Therefore, the question that arises is whether humans alone in the animal kingdom have this ability. If other creatures possess it, what does that mean for their systems of communication, their cognition and the evolution of human language?
Studying animal behaviour (just like studying the cognitive abilities of human infants before they can speak) is extremely hard because of the danger of overinterpretation. To take an example from my Amazonian field research, consider the Amazonian horsefly. The bite of this nasty little creature hurts more than most because they (the females only) suck blood by lacerating the skin. What’s worse is that the locations of the bites itch for a good long time afterwards. Hiking through the jungle is almost always rewarded with multiple bites from these pests, along with their partners in crime, mosquitoes, wasps and smaller species of blood-sucking flies. One thing about horseflies, though, is that they seem to know where you are not looking!
On a certain level, it often seems as though Amazonian horseflies must have minds that can figure out human behaviour. While it is true that they seem to use a strategy for choosing a location on the body (clothes are no impediment as they can easily bite through denim jeans and cotton T-shirts) based on an interpretation of other animals’ behaviour, should one then say that horseflies have a plan for sucking blood that is based on interpretation of their victim’s perceptions? Doubtful.
An alternative explanation could simply be that the flies are genetically programmed to bite the relatively darker areas of a victim – the shaded part of their appendages. A shaded part of your body will also be one in which the visibility will be much reduced. People often anthropomorphise and interpret as cognitively designed actions what are in all likelihood physically determined.
Getting back to primates and animals more generally; there are many rigorous studies that avoid overinterpreting animals’ behaviours.5 One of the most problematic issues in the lengthy conversation in science about whether animals have cognitive abilities in any way similar to those of humans is the profoundly circular assumption that cognition requires language, human language at that, and that therefore animals cannot have cognition because they lack language. This is simply declaring by fiat that humans alone have cognition, before research has been conducted. Such ideas are misguided by their anthropocentric framing of the questions.
These views derive from the work of René Descartes in the seventeenth century, who believed that only humans ‘think therefore they are’. Descartes’s views arguably set back studies of human cognition because they discouraged comparative evolutionary studies of mentality. They also affected non-human studies by simply declaring that animals lacked mental lives.
In Descartes’s view, non-humans possess no consciousness, no thought and no feelings. Additionally, his view that human minds are disconnected from bodily experience led instinctively to his linguistic-based theory of cognition, namely that only language users think.
But as philosopher Paul Churchland aptly puts it: ‘Among many other defects, it [the account that only humans think because thinking requires language] denies any theoretical understanding whatever to nonhuman animals, since they do not traffic in
sentential or propositional attitudes.’6
Any view of cognition that ignores non-human animals ignores evolution. Whether we are talking about the nature of ineffable knowledge or any other kind of cognitive or physical capacity, our account must be informed by and be applicable to comparative biology if it is to have any explanatory adequacy. Animal cognition helps understand the importance of evolutionary theory and comparative biology in the understanding of our own cognition. It also allows for tremendous insight into how the bodies of both humans and other animals are causally implicated in their cognition.
The main problem with disregarding animal cognition is that, in doing so, we are essentially disregarding what cognition might have been like among our ancestors before they got language. Their prelinguistic state was the cognitive foundation that language emerged from. If there is no cognition before language, à la Descartes and many others, the problem of understanding how language evolved becomes intractable.
Of course, there are those who claim that language did not evolve gradually, so we wouldn’t expect to find its roots in any other species. According to such researchers, the grammatical core of language ‘popped’ into being via a mutation, bringing forth a linguistic Prometheus whose X-Men genes spread quickly throughout the entire species.
On the other hand, there are those who work experimentally to address the question of whether primates have beliefs and desires and whether other primates are capable of ‘mind-reading’. For both questions the evidence so far answers tentatively ‘yes’ – there does seem to be some form of these abilities in other primates.
So humans may not be alone in the world of thinking and interpreting others. But if other primates, such as chimpanzees with their 275–450cm3 brains, are capable of reading the intentions of other creatures, as well as holding beliefs and desires, then surely the 500cm3-brained primates of the genus Australopithecus or the 950–1,400cm3-brain-sized species of Homo had even more well-developed powers of cognition and social understanding.
Animals and fossils strongly support the idea that humans got their unique abilities by baby steps. And our debt for this knowledge goes back to the fossil hunters. The painstaking work of collecting fossils and attempting to piece together cultural and anatomical evidence for the origins of our species takes physical fortitude – to withstand the heat, sweat, remoteness and occasional danger of palaeontological field research. It is a cut-throat, competitive enterprise at times, with mudslinging from all sides.
But in spite of the hard, painstaking field research of palaeontologists, on 1 January 1987 an article appeared in the journal Nature which threatened to wrest all the glory, power and science from the palaeoanthropologists and transfer it to lab-coat-wearing geneticists. The paper, ‘Mitochondrial DNA and Human Evolution’, co-authored by Rebecca L. Cann, Mark Stoneking and Allan Wilson, argued that genetic evidence clearly established that the DNA of all current Homo sapiens traces back to a single female’s mitochondrial DNA about 200,000 years ago in Africa.
This was a bombshell. Could it really be that three people in a comfortable laboratory put an end to the controversy surrounding the ‘recent out of Africa’ vs ‘multiregional’ hypotheses? To review, the former claimed that Homo sapiens originated in Africa and migrated out, replacing other Homo species across the globe. The latter suggested that all modern humans evolved in separate lineages from the various sites of Homo erectus around the world.
It turned out that the multiregional hypothesis was shown to be largely incorrect. When it first became public, the ‘Mitochondrial Eve’ theory was met by criticism from the proponents of the multiregional hypothesis, among others. But it has held up well to scrutiny and is now accepted widely by palaeoanthropologists, biologists and geneticists. The lab workers beat the field workers on this one.
Before one can grasp the significance of Mitochondrial Eve for language origins, however, it is necessary to review the science behind the conclusions. This is the theory that underlies the notion of a molecular clock on which the Mitochondrial Eve story is based. Originating sometime in the early 1960s and first published in a paper by Linus Pauling and Emile Zuckerkandl, the molecular clock idea came about after noticing that changes in amino acids across species are temporally constant. Thus, knowing the differences in amino acids between two species can tell when these species split from a constant ancestor.
As with most scientific discoveries, several people soon added to these ideas. Then in 1968 Motoo Kimura published a now famous article, ‘Evolutionary Rate at the Molecular Level’, in Nature. Kimura’s paper laid out the basic ideas of a ‘neutral theory of molecular evolution’. The neutral theory here is non-Darwinian, meaning that, rather than natural selection, Kimura placed the responsibility for most evolutionary change on genetic drift produced by random, neutral variations in organisms. Since these changes do not affect the survivability of an organism, it is able to pass on its genes normally to viable and fertile offspring.
Applying the molecular clock to mitochondrial DNA collected from humans around the world led to the proposal that all living Homo sapiens come from a single woman (called ‘Lucky Woman’ or ‘Mitochondrial Eve’) in Africa, about 200 millennia ago. In other words, only one woman from the past produced an unbroken line of daughters up until the present, thus transmitting her mitochondrial DNA to all living humans.
The genus Homo thus arose in Mother Africa. But if life was so good in Africa, why, when and how did our Homo ancestors leave there?
* Humans are able to run down game for several reasons. First, unlike any quadruped, humans are able to breathe hard while running. Second, humans’ lack of fur, their perspiration, and their upright posture (with its greater surface area exposed to evaporation of perspiration) allow them to cool far more efficiently than quadrupeds. A human running after a horse, other things being equal, will eventually catch it.
3
The Hominins Depart
We travel, some of us forever, to seek other states, other lives, other souls.
Anaïs Nin
THE GREATEST HUNTER. The greatest communicator. The most intrepid traveller. Perhaps the greatest distance runner on earth, Homo erectus was the unsurpassed marvel of its time. No other creature has ever contrasted more starkly with all the animals that had ever lived. Neanderthalensis and sapiens were born from and first lived in the shadow of erectus. We were not new. They were. Sapiens are just the improved model of Homo. Erectus was the first to journey. They were the original imagination-motivated travellers.
Of course, travel itself did not begin with Homo. Many species move from one environment to another. Migration sets up competition with the local species. The genus Homo is no different. Yet so early did Homo begin to travel that, although they originated in Africa, their first fossils were found not there but in Asia – in Indonesia and China. Later, the fossils of other Homos were discovered in Europe – in Spain, France and Germany. How did these fossils come to be in these places? It seems like a nearly impossible task for humans to actually walk around the world. But they did. And for Homo, with its nearly unprecedented endurance, the trip wasn’t as hard as it sounds.
Initially erectus and other Homo species were hunters and gatherers. As such, they needed to move frequently as they exhausted the edible flora and fauna of a given region in a relatively short period of time. Hunter-gatherers usually move a bit further each day from their original village. They may sometimes return to an established camp, but as food becomes ever scarcer in the area surrounding the original village, hunter-gatherers move to establish new settlements closer to their fresher sources of proteins and plant foods.
The average forager travels just over nine miles (fifteen kilometres) per day. Assume that they move communities around four times per year and that each new village is a day’s foraging from the last village. That is thirty-seven miles (sixty kilometres) per year. How long, at that rate, would it take an erectus community to travel from Africa to Beijing or Indonesi
a, both locations where erectus fossils were found? Well, if one divides 10,000 kilometres (roughly the distance from East Africa to where erectus fossils have been found in China) by sixty (the number of kilometres erectus would, under my extremely conservative calculation, move in a year), then it would take only 167 years for erectus to traverse Eurasia, moving at a normal pace. But if erectus populations had other reasons to travel, such as to escape hostile neighbours or climatic events such as flood or drought, they might have moved even more quickly, potentially reducing the time needed in the extreme case to as little as a year. Likewise, if they moved more slowly due to, say, the discovery of rich food supplies in a place along their route, then a larger period of time would elapse. It was, in any case, easily within the grasp of erectus to settle large regions of the world within only a thousand years, a trivial amount of time from an evolutionary perspective.
In the course of their earliest journeys, erectus populations would never have encountered any other humans. They were the first to arrive at every destination. They had all the natural resources of the world before them, with all the land they saw at their disposal. Homo erectus men and women were the greatest and most fearless pioneers of our species.
How Language Began Page 6