The Best Australian Science Writing 2014 (25 page)

Postscript:
This article was published in
The Weekend Australian Magazine
on 6 April 2013. Professor John Mainstone died on 23 August 2013. The ninth pitch drop touched down on 17 April 2014.

The now delusion

Reached by committee, nineteen eighty-three

Uniquely human

Thomas Suddendorf

This is about you, what you are, and how you got here. Biology puts beyond doubt that you are an organism. Like all living organisms, humans metabolise and reproduce. Your genome uses the same dictionary as a tulip and overlaps considerably with the genetic make-up of yeast, bananas, and mice. You are an animal. Like all animals, you have to eat other organisms – whether plant, fungus, or animal – for sustenance. You tend to approach things you want to eat while avoiding things that want to eat you, just as spiders do. You are a vertebrate. Like all vertebrates, your body has a spinal cord that leads up to the brain. Your skeleton is based on the same blueprint – four limbs and five digits – as that of a crocodile. You are a mammal. Like all placental mammals, you grew inside your mother and after birth received her milk (or someone else's). Your body features the same terminal hair as a poodle. You are a primate. Like other primates, you have an immensely useful opposable thumb. Your view of the world is based on the same colour vision as that of a baboon. You are a hominid. Like all hominids, you have shoulders that allow your arms to fully rotate. Your closest living animal relative is a chimpanzee. Yet it would be prudent of me to call you an ape only from a safe distance.

Humans tend to think of themselves as better than, or at least separate from, all other species on this planet. But every species is unique, and in that sense humans are no different. In the tree of life each species is a distinct branch with characteristics that set it apart from others. Humans differ from chimpanzees and other primates in some notable respects. We can lock our knees straight, have longer legs than arms, and habitually walk upright, freeing our hands to do things other than carry our weight. We have a chin. Our body surface is covered in sweat glands that provide a more effective cooling system than those of other primates. We have lost our canines and much of our protective fur, leaving males with the apparently pointless, but persistent, growth of beards. The iris of our eyes is relatively small and surrounded by white rather than dark sclera, making it easy for us to identify the direction of another's gaze. Human females show no outward markers of their fertile phase, and human males lack a penis bone.

These are not exactly groundbreaking traits, compared to, say, the emergence of wings in birds, which predictably catapulted their bearers into a new sphere of possibility. Yet despite the paltry list of distinct physical attributes, we have managed to seize control of much of the planet. That is because our extraordinary powers do not derive from our muscles and bones but from our minds. It is our mental capacities that have allowed us to tame fire and invent the wheel. They enable us to construct tools that make us stronger, fiercer, faster and more precise, resilient and versatile than any beast. We build machines that speed us from one place to the other, even to outer space. We investigate nature and rapidly accumulate and share knowledge. We create complex artificial worlds in which we wield unheralded power – power to shape the future and power to destroy and annihilate. We reflect on and argue about our present situation, our history, and our destiny. We envision wonderful, harmonious worlds as
easily as we do dreadful tyrannies. Our powers are used for good as they are for bad, and we incessantly debate which is which. Our minds have spawned civilisations and technologies that have changed the face of the Earth, while our closest living animal relatives sit unobtrusively in their remaining forests. There appears to be a tremendous gap between human and animal minds, the nature and origin of which fascinated philosophers and researchers for centuries.

Take Bertrand Russell. Like many a scholar before and since, he confidently asserts that certain traits – ‘speech, fire, agriculture, writing, tools and large-scale cooperation' – set humans apart from animals. Although we appear to excel in many domains, such claims are not typically founded in any thorough comparison. In fact, if you set the bar low, you can conclude that parrots can speak, ants have agriculture, crows make tools, and bees cooperate on a large scale. We need to dig deeper to understand to what we owe our unique success. Over the past ten years I have surveyed the scientific evidence regarding the abilities most commonly cited as uniquely human: language, foresight, theory of mind, intelligence, culture and morality. It turns out that in each of these domains, various nonhuman species have competences, but human ability is special in some respects – and they have much in common.

In all six domains I've repeatedly found two major features that set us apart: our open-ended ability to imagine and reflect on different situations, and our deep-seated drive to link our scenario-building minds together. It seems to be primarily these two attributes that carried our ancestors across the gap, turning animal communication into open-ended human language, memory into mental time travel, social cognition into theory of mind, problem solving into abstract reasoning, social traditions into cumulative culture and empathy into morality.

Humans are avid scenario builders. We can tell stories,
picture future situations, imagine others' experiences, contemplate potential explanations, plan how to teach, and reflect on moral dilemmas. Nested scenario building refers not to a single ability but to a complex faculty, itself built on a variety of sophisticated components that allow us to simulate and to reflect.

A basic capacity to simulate seems to exist in other animals. When rats are in a well-known maze, the sequential firing of so-called place cells in the hippocampus suggests that the rats can cognitively sweep ahead, considering one path and then the other, before making a decision about where to go. Appropriate placecell sequences have also been recorded during sleep and rest, suggesting a neural basis for the learning of the maze layout and its options. The challenges of navigation may well have selected for the fundamentals of mental scene construction. Moreover, great apes have demonstrated several other relevant capacities. They can think about hidden movements, learn and interpret human symbols, solve some problems through mental rather than physical computation, have complex sociality and some traditions, console each other, recognise themselves in mirrors, and show signs of pretence in play and deception. Great apes have a basic capacity to imagine alternative mental scenarios of the world. In certain contexts their abilities are comparable to those of 18- to 24-month-old human children.

Human development of mental scenario building explodes after age two, however, while great apes' capacities do not. Children spend a considerable amount of their waking life in fantasy play. They conjure up and untiringly repeat scenarios with props such as dolls and toys. Thinking, in a fundamental way, is imagining actions and perceptions, and it has been argued that in play children test hypotheses, consider probabilities and make causal inferences not entirely unlike (adult) scientists. Play certainly provides opportunity to practise, to build up expectations and to test them. Children take on roles and act out narratives
of what happens in certain situations. Gradually, they learn to deliberately imagine scenarios and their consequences without having to act them out. They learn to simulate mentally. They learn to think.

Eventually, children can imagine an almost limitless array of events. They begin to deploy counterfactual reasoning in which they contrast what did happen with scenarios of what did not happen. They increasingly consider what might happen in the future. A key to our open-ended, generative capacity is our ability to recursively embed one thing in another, as it enables us to combine and recombine basic elements such as people, objects and actions into novel scenarios. Such nesting is also essential for reflection: our capacity to think about our own thinking. Nested thinking allows us to reason about the mental scenarios we entertain (just as we can draw pictures of ourselves drawing a picture).

We can connect diverse scenarios into larger plots. Narratives provide us with explanations for why things are the way they are and with opportunities for predicting how they will be. We can compare alternative routes to the future and deliberately select one plan over another – giving us a sense of free will and an edge over creatures with less foresight. We can prepare for whatever may lie ahead and actively shape the future to our design. However, this capacity also burdens us with the responsibility of getting it right.

Individual simulation is flexible and powerful but also a risky way of making decisions that can lead us fatally astray. In the heat of Australia's north a river may appear inviting for a swim – until you note the sign about the crocodiles. Individually, we often miscalculate, harbour false expectations, and become confused as to which option to pursue. Nested mental scenario building is not a crystal ball, nor is it a logical supercomputer. For flexible scenario building to really take off as the ultimate survival strategy, it required a second leg to stand on.

Our ancestors discovered that they could dramatically improve the accuracy of their mental scenarios by increasingly connecting their minds to others. We give each other advice – for instance, by posting signs about the possible presence of crocodiles. We can broadcast our imaginary play not only throughout our own system but to others around us. We exchange our ideas and give feedback. We ask others, and we inform them – for instance, by recounting what it was like when we were in a similar situation. We take an interest even without knowing whether anything important or useful comes of it. There are individual differences in how much an interest people display in what certain others have to say, but we are generally driven to wire our minds to those around us. Our expectations and plans are subsequently a lot better than they could have been if we didn't listen. It is generally good advice to consider advice – preferably from a variety of sources – before making up your own mind.

Nested scenario builders can benefit from cooperating with other scenario builders in many other ways. For instance, our audience can be recruited for common goals. We can hatch complex plans, divide labour, and pledge cooperation. We can accumulate our achievements and pass them on to the next generation. To ensure all this happens, we appear to be hardwired with an insatiable urge to connect our minds.

Primates are social creatures, and evidence that social pressures have driven the evolution of primate intelligence is mounting. Humans have taken this sociality to another level. Unlike other primates, children sob to attract attention and sympathy. We ask what's wrong and try to make things better. We look each other in the eye, share what's on our minds, and absorb what is on the other's. This urge to connect must have been crucial to the establishment of signs and words that allow us to effectively read others' minds and express our own. We are driven to wire our mental scenario builders into large systems of scenario
builders. We can learn from others' experience, even secondor third-hand. Our drive ultimately led to today's networks of mobile phones and social media that let us exchange our minds across the globe.

As Michael Tomasello and his colleagues have demonstrated in many studies on apes and children, we make and pursue shared goals where our closest animal relatives do not. Even two-year-old children outperform great apes on tasks of social learning, communication and intention reading. Other animals may give alarm calls and food calls but otherwise do not show many signs of a drive to share their experience and knowledge with others. Again, in all six domains this cooperative drive is evident and plays a significant role. Language is the primary means by which we exchange our minds. We talk to each other about the past and make plans about the future. We read and tell each other what is on our minds. We reason and solve problems collectively. We build social narratives that explain the world around us. We teach, and we learn from each other. And we argue about what is right and what is wrong. These examples serve to remind us how pervasive the urge to connect is. Those who lack this drive have severe social difficulties (and may be diagnosed as autistic). Our urge to connect was essential for the creation of cumulative cultures that shape our minds and endow us with our awesome powers.

Our capacity for nested scenario building even allows us, drawing on past experiences, to imagine others' advice internally. (Hearing voices is quite normal. Relax. The trouble starts when you attribute these internal voices to external sources.) So you might ask yourself what your mother would have said about the situation you find yourself in. We care about whether our parents, friends, heroes or gods would be proud of what we do, even if they no longer exist (or never did). We can consider what others might remember us for. These thoughts can be important
drivers motivating us to go beyond satisfying immediate personal self-interests in pursuit of ‘higher' notions of honour, valour and glory.