What makes us human? I suggest that most of the things that differentiate us from our nearest evolutionary relatives spring directly or indirectly from one simple cognitive trick: we can travel mentally in time.
Anyone who has trained a dog knows that rewards and punishments must always follow directly the behaviour that you wish to encourage or discourage; otherwise the dog will not make the connection. Dogs have very good memories in the sense of being able to recognise people and places, even after a long gap in time, but they do not seem able to recall a past event and relate it logically to a different event in the present.
Some unfortunate humans cannot do this either as a result of brain damage. Significantly these people seem incapable of plannning for the future either, suggesting that we use the same cognitive function whether we are travelling forwards or backwards in time.
Apes certainly don’t plan for the future. No chimpanzee gets up in the morning, fashions a termite-fishing rod and goes off to find a termite mound. Chimpanzee tools are always made in situ, in response to a perceived need, and then abandoned when that need has been satisfied. That is one reason why chimps do not make tools more complex than a stripped twig to fish for termites or a sponge of torn-up leaves to sop up water from a hollow stump. It would simply not be adaptive to spend much time and effort making a durable tool which would then be used only once.
Another reason why apes do not make stone tools is that, in order to do so, you first have to learn how. Apes cannot learn anything that is not immediately rewarding. They can be taught to knap flints in the laboratory, where they are rewarded with fruit at every stage of the process. In the wild the only reward for such learning is the indirect one of knowing that you will be able to make a tool later, when you need it. In order to work for an indirect reward, you need to be able to visualise the future.
The entire history of human technology can be summed up as a greater and greater degree of indirectness in the rewards for which we work. For example, modern humans prospect for oil in order to extract it from the ground, in order to turn it into plastics, in order to make polythene bags to carry food home from the supermarket.
Technology plans for the future; science looks to the past. Animals can recognise correlations only between events which are nearly simultaneous. Even a ten-second delay between action and reward can be too long when training a dog. But once you can consciously remember the past, you have an almost infinite number of sets of events to test for reliable correlations. This makes it possible to move from the concept of correlation to that of causation. A is always followed by B because A causes B. From there it is a short hop to causality, the idea that all events have causes and that these causes can in principle be discovered. And what, after all, is science but a refinement of that insight?
The ability to remember the past also gives us that unique human invention, the biographical self. Basic self-awareness first appears (at least in our lineage) with the apes. A monkey cannot recognise its own reflection in a mirror but an ape can. Significantly, apes have also been observed deceiving each other, which monkeys never do. In order to deceive, you need a theory of mind: that is, you must recognise that other members of your species are also centres of consciousness. Self-awareness is a necessary precondition for theory of mind though not apparently a sufficient one (autistic people have great difficulty in taking this step and severe autists never make it).
If I have self-awareness and I can recall my past, then my self has a biography. It is quite definitely my self, not just any old self. I can remember a great deal of what has happened to me and how I came to be the person I am, and this converts the simple biological urge to survive into an intellectual conviction that I have intrinsic value and should be protected from harm and exploitation. If, in addition, I have a theory of mind, then I can see that logically other people must have the same kind of value and the same rights. And so morality is born.
It is often claimed that animals also have a kind of morality. Certainly they often behave in ways that suggest mutual altruism. For example, vampire bats will regurgitate blood to feed a comrade who has failed to find a blood meal that night. But they do so in the hope of future favours. The true law of the jungle is “Do as you have been done to” or “tit for tat!”. This doesn’t require any belief in the consciousness or rights of others; it’s merely a strategy for optimal survival within a group. A computer can be programmed to apply it, and it has been shown mathematically to be an optimal strategy for all social situations in which other members of your group may respond unpredictably to your needs.
This is different in its very essence from the Golden Rule of “Do as you would be done to ” and also from Hilel’s earlier and less-known Silver Rule: ‘Whatever seems vile to you, do not do it to others”. Both these rules are based on a conscious evaluation of other selves as having logically the same rights that one has oneself. Neither is in any sense a strategy for survival. On the contrary, human moral behaviour often contradicts not just immediate but also long-term self-interest, and is most highly praised when it does so. It makes no sense without a theory of mind.
My awareness of myself as a continuing entity with a past also interacts with the results of my travelling in time in the opposite direction. I know, as a mere beast does not, that I have a finite lifetime and that there will come a time when I will die. This leads me to wonder about what will happen to me when I die. Will I just cease to exist? Will I continue to exist in some other dimension? If there is an afterlife of some kind, will I have to answer to anyone there for the things I did in this life? And if there is no afterlife, what is the value and purpose of my life in this world? Such questions are asked by every human being, and they lead naturally to religion and metaphysics.
Science and technology, biographical memory and awareness of a continuing self, morality and religion, philosophy and political beliefs about human rights, awareness of death and speculation about an afterlife — everything that is specifically and undeniably human springs from this one root. If I am sitting here, fully clothed, typing philosophical speculations into a computer, and not swinging, naked and hairy, from a branch in a tropical forest canopy, it could be ultimately because our ancestors learned this one simple trick of time travel.
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