We had assumed we were the only animal to wage war and to kill our fellows. But in 1974 the chimps of Gombe (and subsequently most other colonies studied in Africa) put paid to that theory by raiding silently into the territory of neighbouring troops, ambushing the males and beating them to death.
We still believed we were the only animal with language. But then we discovered monkeys have a vocabulary for referring to different predators and birds, while apes and parrots are capable of learning quite large lexicons of symbols. So far there is nothing to suggest that any other animal can acquire a true grasp of grammar and syntax, though the jury is still out for dolphins.
Some scientists believe that chimpanzees do not have a ‘theory of mind’: that is, they cannot imagine what another chimpanzee is thinking. If so, for example, they could not act upon the knowledge that another individual holds a false belief. But experiments are ambiguous. Chimps regularly engage in deception. In one case, a baby chimp pretended that he was being attacked by an adolescent in order to get his mother to allow him to suckle from her nipple.14 It certainly looks as if they are capable of imagining how other chimps think.
More recently, the argument that only human beings have subjectivity has been revived. The author Kenan Malik argues that ‘humans simply are not like other animals and to assume we are is irrational…Animals are objects of natural forces, not potential subjects of their own destiny.’ Malik’s point is that because we, uniquely, possess consciousness and agency, so we alone can break out of the prison of our heads and go beyond a solipsistic view of the world. Yet I would argue that consciousness and agency are not confined to human beings, any more than instinct is confined to non-human animals. See almost any passage of Goodall’s books for evidence. Even baboons have recently performed well enough at computer discrimination tasks to show they are capable of abstract reasoning.15
This debate has been running for more than a century. In 1871 Darwin drew up a list of human peculiarities that had been claimed to form an impassable barrier between man and animals. He then demolished each peculiarity one by one. Though he believed only man had a fully developed moral sense, he devoted a whole chapter to the argument that a moral sense was present, in primitive form, in other animals. His conclusion was stark:
The difference in mind between man and the higher animals, great as it is, is certainly one of degree and not of kind. We have seen that the senses and intuitions, the various emotions and faculties, such as love, memory, attention, curiosity, imitation, reason, &c., of which man boasts, may be found in an incipient, or even sometimes in a well-developed condition, in the lower animals.16
Wherever you look there are similarities between our behaviour and that of animals, which cannot be simply swept under the Cartesian carpet. Yet, of course, it would be perverse to argue that people are no different from apes. The truth is we are different. We are more capable of self-awareness, of calculation and of altering our surroundings than any other animal. Clearly, in some sense, this sets us apart. We have built cities, travelled in space, worshipped gods and written poetry. Each of these things owes something to our animal instincts – shelter, adventure and love – but that rather misses the point of them. It is when we go beyond instinct that we seem most idiosyncratically human. Perhaps, as Darwin suggested, the difference is one of degree rather than kind; it is quantitative, not qualitative. We can count better than chimpanzees; we can reason better, think better, communicate better, emote better, perhaps even worship better. Our dreams are probably more vivid, our laughter more intense, our empathy more profound.
Yet that leads straight back to mentalism, equating an ape with an apprentice person. Modern mentalists have diligently tried to teach animals to ‘speak’. Washoe (a chimp), Koko (a gorilla), Kanzi (a bonobo) and Alex (a parrot) have all done remarkably well. They have learned hundreds of words, usually in the form of sign language, and have learned to combine them into primitive phrases. Yet, as Herbert Terrace pointed out after doing the same with a chimpanzee called Nim Chimpsky, all these experiments have taught us is how bad these animals are at language. They rarely even rival a two-year-old child, and they seem incapable of using syntax and grammar except by accident. As Stalin is reputed to have said of military force, quantity has a quality all its own. We are so much better at language than even the cleverest ape that it really could be called a difference of kind, not degree. That is not to say it does not have roots and homologies in animal communication, but then a bat’s wing has homology with a frog’s front foot, and a frog cannot fly. To concede that language is a qualitative difference does not imply that we can set human beings apart from nature, though. Trunks are unique to elephants. Spitting venom is unique to cobras. Uniqueness is not unique.
So which are we, similar to apes or different from apes? Both. The argument about human exceptionalism, today as in Victorian times, is mired in a simple confusion. People still insist that their opponents must take sides: either we are instinctive animals, or we are conscious beings, but we cannot be both. Yet both similarity and difference can be true at the same time. You do not have to abandon an ounce of human agency when you accept the kinship of our minds with those of apes.17 Neither similarity nor difference wins; they coexist. Let some scientists study the similarities while others study the differences. It is time we abandoned what the philosopher Mary Midgley has called ‘the strange segregation of humans from their kindred that has deformed much of enlightenment thought’.18
SEX AND ITS EFFECTS
There is one way in which behaviour seems to evolve differently from anatomy. In the case of anatomy, most similarities are the result of common descent, or what evolutionists call phylogenetic inertia. For example, human beings and chimpanzees both have five digits on each hand and foot. This is not because five is the perfect number for the lifestyle of both species, but because among the early amphibians, one happened to have five digits and most of its myriad descendants, from frogs to bats, have not altered the basic pattern. Some, like birds and horses, do have fewer digits, but none of the apes do.
The same is not true of social behaviour. By and large, ethologists have found very little phylogenetic inertia in social systems. Closely related species can have very different social organisation if they live in different habitats or eat different food. Distant relatives can have very similar social systems by convergent evolution if they inhabit similar ecological niches. Where two species show similar behaviour, it tells you less about their common ancestor and more about the pressures of the environment that shaped them.19
A good example is the sex life of the African apes. As primatologists delved further into the lives of apes, they found that alongside the similarities were some intriguing contrasts. These contrasts were thrown into sharper relief by the studies of George Schaller and Diane Fossey on gorillas, Birute Galdikas on orang-utans and the later studies of Takayoshi Kano on bonobos. In the zoo, a chimp looks a bit like a small gorilla. The skeletons of large chimpanzees have been confused with those of small gorillas. In the wild, however, there is a marked difference in their behaviour. It all starts with diet. Gorillas are herbivores, eating the stems and leaves of green plants such as nettles or reeds as well as some fruit. Chimpanzees are principally frugivores, seeking out fruit in trees, but adding ants, termites or monkey meat when they can. This difference in diet dictates a difference in social organisation. Plants are abundant but not very nutritious. To thrive on them, a gorilla must spend nearly all day eating and need not move very far. This makes a group of gorillas rather stable and easy to defend. This in turn has tempted male gorillas into evolving a polygamous mating strategy: each male can monopolise a small harem of females and their immature young, driving away other males.
Fruit, however, appears unpredictably in different places. Chimpanzees need to have large home ranges to be sure of finding a fruiting tree. But when a tree is found there is plenty of food to go round, so the animals can share their home range with many other chimps. But because