Tree of Origin: What Primate Behaviour Can Tell Us about Human Social Evolution 
edited by Frans de Waal.
Harvard, 311 pp., £20.50, August 2001, 0 674 00460 4
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The Ape and the Sushi Master: Cultural Reflections by a Primatologist 
by Frans de Waal.
Allen Lane, 433 pp., £16.99, June 2001, 0 7139 9569 6
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Asked​ whether any single word would serve as a prescription for all one’s life, Confucius proposed ‘Reciprocity’. Jesus said it in a few more words: ‘Do unto others as you would have them do unto you.’ They weren’t the first. A ‘black-haired, big-jawed, knuckle-walking species, that ate seasonally available soft, ripe rainforest fruits’ probably had a similar code of conduct. That was our ancestor of some six to eight million years ago, also the grandparent of our two closest modern cousins: bonobos and chimpanzees. Knuckle-walking and the like have been inherited today by chimps, bonobos and a more distant relative, the gorilla. This ancestor must also have had (in some form or other) three traits shared by all of its present-day descendants: intelligence, co-operation, and the rudiments of culture.

The description of what we might call Pan prior, ‘the first chimpanzee’, is from an essay by Richard Wrangham in Tree of Origin. Like The Ape and the Sushi Master, Tree of Origin proposes that we (human beings) share with our near primate cousins some of the behaviour we like best in ourselves. Professional primate-watchers are usually wary of venturing into fuzzy areas of human evolution. We all do it, but clutching Zimmer frames of jargon in case we stumble. Frans de Waal steps out and puts his opinions on the line. He has also persuaded eight of his most distinguished colleagues to do the same.

De Waal is one of the subtlest, most knowledgeable and most cheerful students of great ape behaviour. He broke through the professional/popular barrier in 1982 with his first book, Chimpanzee Politics, and has been punching holes in it ever since. In The Ape and the Sushi Master, a book that aims to make you proud to be a primate, he draws from his own experience with aggressive chimpanzees, sexy bonobos, hierarchical rhesus macaques and coalition-building stumptailed and Tibetan macaques.

De Waal is not mawkish. He despises the ‘Bambification’ of animals. The chimpanzees he watches have been known to kill each other. They have castrated their rivals. But chimpanzees also hug and kiss in reassurance and friendship. After fights, they are likely to make up with extra shows of affection. They need each other, and they seem to know it. Bonobos go further. They defuse tension, within and between groups, by sexual contact – with anyone, in any position, of any age. It would be child abuse to deprive an infant bonobo of sex. Tree of Origin describes in some detail chimpanzee and bonobo society, as well as that of muriquis, the most ape-like monkeys, and speculates about possible stages in the transition to humanity: hunting and meat-sharing, root-digging and cooking, minds that could learn programmes of behaviour, brains that could evolve language and, finally, culture.

In The Ape and the Sushi Master, de Waal points out that Darwin, like Aristotle and Aristotle’s contemporary, the Chinese sage Mencius, thought kindness and co-operation must be based on natural instincts. It was Huxley, he writes, who distorted Darwinism into ‘nature red in tooth and claw’. Nowadays, the metaphor of the ‘selfish gene’ has done much to purge the wishful thinking that genes, or animals, will sacrifice themselves for larger wholes like the good of the species. However, if genes gain reproductive advantage by co-operation instead of competition, fine – they go for co-operation. De Waal moves up several levels from genes and genomes to explore how individual animals may have evolved to want to help each other.

He has a wonderful photograph of a dog stepping daintily over the head of a recumbent tiger, who opens an eye to look up as she passes. They live together in a zoo in Thailand. Zookeepers gave three tiger cubs to the dog to suckle along with her own puppy. De Waal points out that she sacrificed energy that could have been devoted to her own potential reproductive effort, because she had evolved nurturing instincts for needy babies, even if they did smell funny and have stripes. The grown tigers now observe one of our own rules: honour your mother, and don’t eat her. She is top dog in the group. (The tigers haven’t lost their predatory instincts: de Waal watched uneasily as their yellow eyes followed the three-year-old human child he took to the zoo.)

It is easy to see why parents’ care for children and children’s respect for parents have evolved. How far such feelings spread varies from species to species. A wolf or a wild dog suckles her pack-mate’s young, and, it is said, even human wolf-children. A sheep, on the other hand, defends herself against rearing others. Lambs run through the whole herd, and could easily steal milk if allowed to. But a ewe learns her own new-born’s smell as she licks off the birth fluids. After that she will suckle no other lamb, butting away any interlopers. Primates, like dogs, are good adopters. Within a monkey troop, or even among ring-tailed lemurs, females may nurse and carry the young of related females. Orphans who are old enough to feed themselves can be reared by other animals – even by males. Not always, of course, but often enough to suggest it’s a widespread trait of our whole lineage. Two cases of human children falling into gorilla enclosures at the zoo have hit the newspaper headlines. Jambo, a silverback in Jersey, stood guard over an unconscious five-year-old until help came. Binti Jua, a female in Chicago, picked the baby up and carried it back to the door to give to her keepers. As de Waal points out, it is nonsense to think that gorillas, famous for long-term individual recognition, and in Binti Jua’s case with her own baby on her back, might not distinguish a little blond boy in red trainers from a gorilla infant. It’s just that many primates like babies – even those of other species.

What about less dramatic kindnesses: you groom me, I groom you; you groom me, I help in your next fight – Confucius’ reciprocity? Reciprocity is one of the facts of troop life all through the primate line. Of course, alliances are often conditional. De Waal tells the story of Nikkie’s Ghost. Two males, young Dandy and wily old Yeroen, ganged up to take power in the chimpanzee colony at Arnhem Zoo. They deposed the alpha male, Nikkie, driving him into the moat, where he drowned. With Nikkie gone, Dandy and Yeroen moved into rivalry with each other. A year later, a researcher wanted to know if chimpanzees could recognise pictures of each other. He projected a video of the group onto the wall by their indoor quarters. The chimps were apparently unmoved, until a life-sized image of Nikkie loomed on the wall. ‘Dandy ran screaming to Yeroen, jumping literally in the old male’s lap . . . Nikkie’s mysterious resurrection had temporarily restored their old pact.’

Reconciliation is usually more subtle. After a fight, or a little spat, two opponents may seek each other out for grooming. Reconciliation is common among chimpanzees and bonobos. It differs widely among monkeys, according to the prevailing social system and does not seem to exist in lemurs. Arguably, the muriquis studied by Karen Strier are even more given to affiliation. Muriquis are the largest New World monkeys, South America’s nearest ecological equivalent to the apes. In their male-bonded groups males compete indirectly by the quantity (and perhaps quality) of their sperm. They don’t fight each other, so they don’t need to make up – but, like chimps, they hug and cuddle when meeting. Even more complicated is mediated reconciliation. In Chimpanzee Politics, de Waal describes the way Old Mama, the lead female of the Arnhem Zoo colony, would make peace between two feuding males. She would inch back towards one while grooming the other, and the one being groomed would follow to keep in reach of her clever hands. Then, as she was sitting between the two enemies, she would slip away, leaving them with no choice but to groom each other.

It may be easy to accept that there is kindness and co-operation among social animals who live together. It may also be obvious that animals have emotions which can be called love or affection, in the cautious sense that animals seem to want to rehearse the behaviour we associate with friendship and nurturing. The next question is: do primates learn, and transmit, elements of their behaviour? Can an animal community shape its own traditions?

Most examples of such proto-culture have to do with material objects. Jane Goodall’s first published scientific paper was about a ‘fashion’ that swept the Gombe for building night-nests in palm trees. Kinji Imanishi, the guru of Japanese primatology, suggested in 1953 that animals might have ‘culture’, which he defined as ‘socially transmitted adjustable behaviour’. In 1954, 18-month-old Imo made her first innovation, wading into the water with a sweet potato and rubbing the mud off it. Satsue Mito saw her. Mito was a farmer’s daughter hired by the academic researchers to tame the monkeys and to learn to recognise individuals. Now 84, she is an officially designated ‘national treasure’ for her work in primatology. She documented the spread of potato-washing: it took five years for three-quarters of the troop to adopt the new behaviour. Shunzo Kawamura and Masao Kawai also collected data, and published papers, though it was not until 1965 that Kawai publicly called it ‘pre-cultural’ behaviour.

In 1992, William McGrew summarised chimpanzee tool differences in different regions. West African chimps crack nuts using stones as hammers, and other stones or tree-roots as anvils. East African chimps do not. The same nut-tree species grow in East Africa, there are plenty of rocks, and there is no immediate dietary substitute. The East African chimps have both opportunity and motive; they just do not have a tradition that teaches them how to crack nuts. In 1999 all chimp fieldworkers (organised by Andrew Whiten) got together to catalogue known differences between local cultures. It turns out that every single population of chimpanzees differs from all others in some aspects of its toolkit, and also in social quirks – grooming with one hand clasped overhead within the partner’s, for example. In the current issue of Folia primatologica, Tatyana Humle and Tetsuro Matsuzawa reveal that populations of chimps living only 12 kilometres apart, in Guinea and Côte d’Ivoire, may crack different species of nuts, and favour different kinds of tool, even though their habitats have the same trees. My current favourites are the Sierra Leone chimps studied by Rosalind Alp, who carry smooth sticks in their feet so that they can walk on the thorny branches of kapok trees while picking the fruit – Alp calls the sticks ‘footwear’. I am also intrigued by the Mahale Mountains chimps who, when they settle down to groom, first give a few quick scratches to each others’ backs. Other chimps scratch themselves, but not each other. ‘You scratch my back and I’ll scratch yours’ is a local tradition, not a metaphor, for chimpanzees.

It is clear that there is social learning, and tradition with local variations, among the apes (as for various other social animals). The real question is: do apes intend to do any of these things? If an ape is kind, is it kind like a worker ant, like one of our own skin cells, programmed in earlier aeons to be self-sacrificing without choice? Or is it kind in the way that people are kind: innate inclination shaped by social learning, with the implication that other courses of action are possible? Of course the ape, or the human being, who learns a local custom may never imagine that other choices are possible, until someone turns up who points out that other people act differently.

Great apes, it seems, can take account of other apes’ states of knowledge. Sarah Boysen showed each of her chimpanzees a predator approaching the cage of their best friend in the colony. (The predator was a white-coated vet with a dart-gun.) There were two different protocols. Some chimps could observe that their friend could see the looming threat. Others saw that their friend was shut in, and when the door was raised might unknowingly knuckle-walk into danger. The chimps who had no need to warn the friend were relatively quiet; the chimps whose friend needed warning raised Cain. In other words, they were able to take into account the fact that the friend did not know what they knew themselves. This is quite a sophisticated process. Four-year-old human children can do it; three-year-olds, by conventional tests, cannot. Rhesus monkeys, in the same test done by Robert Seyfarth and Dorothy Cheney, did not. (It seems more and more likely that bottle-nosed dolphins and killer whales are like apes and human four-year-olds, not like three-year olds and monkeys.)

Great apes can recognise themselves in mirrors. ‘That, there, is me’ implies some sense that there is a me. Human two-year-olds know themselves in mirrors; monkeys and one-year-olds do not. Great apes practise deception on a level that suggests, again, that they know about others’ ignorance. Apes occasionally imitate each other exactly – even more rarely, they deliberately teach. Christophe Boesch saw a mother chimpanzee take a hammer-stone that her daughter was using awkwardly, position it properly in her own hand, slowly and deliberately crack a nut, and hand it back to her daughter, who then used it correctly herself.

In fact, most of the life skills that people learn are not deliberately taught. McGrew cites a study of the fifty basic skills of Aka pygmies, almost all learned without active teaching. Teaching, he points out, is a last resort: time-consuming, prone to error. Teaching is for the frills of life: really important skills are learned outside school. They are absorbed from watching others, or from trial and error ‘play’ in the company of others. They can be as simple as how to use chopsticks, as complicated as tracking an antelope, as fundamental as learning to talk. As for the apprentice sushi master:

The young man cleans the dishes, mops the kitchen floor, bows to the clients, fetches ingredients, and in the meantime follows from the corners of his eyes, without ever asking a question, everything that the sushi masters are doing. For no less than three years he watches them without being allowed to make actual sushi for the patrons of the restaurant – an extreme case of exposure without practice. He is waiting for the day on which he will be invited to make his first sushi, which he will do with remarkable dexterity.

Apes do not apprentice themselves to masters, though young male chimpanzees may tag after and ‘hero-worship’ an adult role model. It seems, though, that they do have intention, empathy and some knowledge of each other’s knowledge. Furthermore, they have a wide range of kindly emotions, as well as the ability to calibrate them: reciprocating towards friends, reconciling with enemies. Do they ever put these together, to learn to be nicer – or nastier? It seems that daughters may learn and continue their mothers’ own style of mothering. Male chimpanzees of the Taï Forest in the Ivory Coast co-operate when hunting monkeys, while at the Gombe Stream they do not. There is, admittedly, an ecological difference: in the high, closed-canopy Taï rainforest, hunters who did not co-operate would never catch a monkey. There is no proof, yet, that the fundamentals of social behaviour, as opposed to the superficial tricks like mutual back-scratching, can be learned, but all the elements are there.

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