What makes us human is the brain which enables us to ask just this question. We are aware how much we share with the animal kingdom and how close our DNA is to that of the higher mammals. We increasingly hear how much we all have in common with animals. Animals often show at least an equal concern with looking after their young. We know that elephants can grieve, that chimpanzees and other apes learn to use tools and even to share them, so there is the beginning of what we think of as unselfish sharing for mutual benefit. But animals, even those whose DNA is closest to ours, cannot make or control fire.
One wonders how this powerful tool was first discovered, perhaps by primitive man constantly rubbing two dry sticks together in a moment of boredom and producing a spark that lighted a pile of dry leaves. With this apparent miracle a significant step in the long rise to humanity was taken. Fire could be used to frighten away predators, provided the warmth which enabled early man to survive extreme cold and gave him the ability to cook meat and render it more digestible and life-sustaining. The making of fire was one of the most important discoveries which set human beings on the path to domination.
But most people, when faced with the question of what makes us human, give thought to a wider dimension than the difference between Homo sapiens and the animal kingdom, a dimension which includes ethics and morality and the recognition of responsibility for other than the immediate family or species. An animal has no concept of reality outside its own life and that of its young, and its place in the herd. Because we have the capacity to imagine and sympathise with the emotions including the pain of others, surely that implies a responsibility to alleviate suffering and promote well-being among all sentient creatures, including the animals of which we make use for our sustenance, convenience and pleasure.
To describe a person as acting like an animal is an insult, while the expression, “crime against humanity”, implies that there is some behaviour regarded as so appalling that the perpetrator is offending against a recognised code of what is acceptable from human beings. If the offence is committed by a single individual he is commonly labelled a psychopath, a diagnosis which it is seldom possible to follow with effective treatment. If the outrage is committed by a country, as with genocide, international opprobrium and a system of reparation, where this is possible, usually follow. We have the ability, both internationally and at home, to militate against behaviour we view as unacceptable and to make it illegal and punishable by law. We set up complicated legal and social contrivances designed to enable us to live together in peace and safety and which, in all civilised societies, are accepted and incorporated in words. The extent and richness of a country’s language is among the most important measures of its civilisation, and it is primarily language which makes us human.
When we think about what it means to be human, often we are considering what personal preoccupations, ambitions and conduct to others make us unique creatures on the planet. Unlike animals, human beings occupy their minds with concerns outside the compulsions of sex, food, shelter and the herd: the creation of our universe, the possibilities that other planets might sustain life and that eventually we shall make contact with other intelligent beings and communicate with them. We create gods ranging from tribal images in wood and stone to complicated theological arguments, and set up organisations to accommodate these deities and define the obligations of belief and worship.
But in the end the simple difference remains. Over millions of years the Darwinian process of evolution which has given us a Newton, a Shakespeare and a Mozart, has resulted in the human capacity to think, to wonder, to create and to invent. The capacity which enables us to use science to destroy each other in wars is also used to conquer disease, with the risk that we reproduce in numbers which inevitably outstrip the natural resources on which we depend. Unlike animals, we have the means to destroy Planet Earth by our greed, or to make it a safer place in which all living creatures can live.
How should we relate to each other? How do we deal with those aggressive impulses which seem to be in our nature? How do we tolerate people who are different, especially when they come to live among us? How should we educate our young? Is the nuclear family the only right pattern for marriage and parenthood? How can we save the planet which we alone among living creatures have the power to destroy? This is the ultimate question which faces us as humans and it is one of which the animal kingdom is oblivious. It is our responsibility, and it is this responsibility that makes us human.
P D James’s most recent book is “Death Comes to Pemberley” (Faber & Faber, £7.99) This article is the twelfth in our “What Makes Us Human?” series, published in association with BBC Radio 2 and the Jeremy Vine show