mattered not at all. So long as it had a contrasting spot near the tip of the bill, preferably in red, it would elicit pecking. In modern jargon, scientists would say that the chick’s instinct, and the adult’s beak spot had ‘co-evolved’. An instinct is designed to be triggered by an external object or event. Nature plus nurture.22
The significance of Tinbergen’s experiments was to reveal just how complex instincts could be, and yet how simply triggered. The digger wasp he studied would dig a burrow, go and catch a caterpillar, paralyse it with a sting, bring it back to the burrow and deposit it with an egg on top, so that the baby wasp could feed on the caterpillar while growing. All of this complex behaviour, including the ability to navigate back to the burrow, was achieved with almost no learning, let alone parental teaching. A digger wasp never meets its parents. A cuckoo migrates to Africa and back, sings its song and mates with one of its own species without as a chick ever seeing either a parent or a sibling.
The notion that animal behaviour is in the genes once troubled biologists as much as it now troubles social scientists. Max Delbruck, pioneering molecular biologist, refused to believe that his colleague at Caltech Seymour Benzer had found a behavioural mutant fly. Behaviour, he insisted was too complex to reduce to single genes. Yet the idea of behaviour genes has long been accepted by the amateur breeders of domestic animals. The Chinese started breeding mice of different colours in the seventeenth century or earlier and they produced a mouse called the waltzing mouse, famous for its dance-like gait caused by an inherited defect in the inner ear. Mouse breeding then caught on in Japan in the nineteenth century and thence spread to Europe and America. Some time before the year 1900 a retired schoolteacher in Granby, Massachusetts, by the name of Abbie Lathrop, took up the ‘mouse fancying’ hobby. Soon she was breeding different strains of mice herself in a small barn adjoining her property and selling them to pet shops. She was especially fond of what were by then known as Japanese waltzing mice, and she developed several new strains. She also noticed that some strains got cancer more often than others; picked up by Yale University, this hint became the basis of early studies of cancer.
But it was Lathrop’s link to Harvard that uncovered the link between genes and behaviour. William Castle of Harvard bought some of her mice and started a mouse laboratory. Under Castle’s student Clarence Little, the main mouse laboratory moved to Bar Harbor, Maine, where it still is – a giant factory of inbred mouse strains used in research. Very early on, the scientists began to realise that different strains of mice behaved in different ways, too. Benson Ginsburg, for instance, found out the hard way. He noticed that when he picked up a mouse of the ‘guinea-pig’ strain (named for its coat colour), he often got bitten. He was soon able to breed a new strain that had the coat colour but not the aggressive streak: proof enough that aggression was somewhere in the genes. His colleague Paul Scott also developed aggressive strains of mice, but bizarrely, Ginsburg’s most aggressive strain was Scott’s most pacific. The explanation was that Scott and Ginsburg had handled the mice differently as babies. For some strains, handling did not matter. But for one strain in particular, C57-Black-6, early handling increased the aggressiveness of the mouse. Here was the first hint that a gene must interact with an environment if it is to have its effect. Or, as Ginsburg put it, the road from the ‘encoded genotype’ the mouse inherits to the ‘effective genotype’ it expresses passes through the process of social development.23
Ginsburg and Scott both later went on to work with dogs, Scott proving by crossing experiments between cocker spaniels and African basenjis that play-fighting in puppies is controlled by two genes that regulate the threshold for aggression.24 But it did not need science to prove the inheritance of behaviour in dogs: that was old news to dog-breeders. The point of dogs is that they come in different behavioural types: retrievers, pointers, setters, shepherds, terriers, poodles, bulldogs, wolfhounds – their very names denote the fact that they have instincts bred into them. And those instincts are innate. A retriever cannot be trained to guard livestock and a guard dog cannot be trained to herd sheep. It’s been tried. In the process of domestication, dogs have kept incomplete or exaggerated elements of wolf behaviour development. A wolf will stalk, chase, pounce, grab, kill, dissect, and carry food, and a wolf pup will practise each of these activities in turn as it grows up. Dogs are wolf pups frozen in the practising stage. Collies and pointers are stuck in the stalking stage; retrievers are stuck with carrying and pit bulls with biting: each is a frozen mixture of different wolf-pup themes. Is it in their genes? You bet: ‘Breed-specific behaviours are irrefutable,’ says dog chronicler Stephen Budiansky firmly.25
Or go ask the cattle-breeders. I have in front of me a catalogue of dairy bulls designed to entice me into ordering some semen by mail. In enormous detail it describes the quality and shape of the bull’s udder and teats, its milk-producing ability, its milking speed and even its temperament. But surely, you point out, bulls don’t have udders? On every page there is a picture of a cow, not a bull. What the catalogue is referring to is not the bull himself but his daughters. ‘Zidane, the Italian No 1,’ it boasts, ‘improves frame traits and fixes on tremendous rumps with ideal slope. He is particularly impressive in his feet and leg composites with excellent set and terrific depth of heel. He leaves faultless udders, which are snugly attached with deep clefts.’ The characters are all female, but the attribution is to the sire. Perhaps I would prefer to buy a straw of semen from Terminator, whose daughters have ‘great teat placement’, or Igniter, a bull that is a ‘milking speed specialist’ whose daughters ‘display great dairy character’. I might wish to avoid Moet Flirt Freeman, because although his daughters have ‘tremendous width across the chest’ and give more milk than their mothers did, the small print admits they are also slightly ‘below average’ in temperament – which probably means that they tend to kick out when being milked. They are also slow milkers.26
The point is that cattle-breeders have no qualms about attributing behaviour to genes, just as they attribute anatomy to genes. Minute differences in the behaviour of cows they confidently ascribe to the semen that arrived through the mail. Human beings are not cows. Admitting instinct in cows does not prove that human beings are also ruled by instinct, of course. But it demolishes the assumption that because behaviour is complex or subtle, it cannot be instinctive. Such a comforting illusion is still rife within the social sciences; yet no zoologist who has studied animal behaviour could believe that complex behaviour cannot be innate.
MARTIANS AND VENUSIANS
Defining ‘instinct’ has baffled so many scientists that some refuse to use the word altogether. It need not be present from birth: some instincts only develop in adult animals (as wisdom teeth do). It need not be inflexible: digger wasps will alter their behaviour according to how many caterpillars they find already in the burrow they are provisioning. It need not be automatic: unless it meets a red-bellied fish, the stickleback male will not fight. And the boundaries between instinctive and learned behaviour are blurred.
But imprecision does not necessarily render a word useless. The boundaries of Europe are uncertain – how far east does it stretch? Are Turkey and Ukraine in it? – and there are many different meanings of the word ‘European’, but it is still a useful word. The word ‘learn’ covers a multitude of virtues, but it is still a useful word. Likewise, I believe that to call behaviour instinctive can still be useful. It implies that the behaviour is at least partially inherited, hard-wired and automatic, given the expected environment. A characteristic feature of an instinct is that it is universal. That is, if something is primarily instinctive, then it must be approximately the same in all people. Anthropology has always been torn between an interest in human similarities and human differences, with the advocates of nature emphasising the former and the advocates of nurture stressing the latter. The fact that people smile, frown, grimace and laugh in much the same way all over the world struck Darwin and would later strike the ethologists
