With the extra room at the farm, Lyudmila also began breeding a population of control foxes, which would allow her and Dmitri to make rigorous comparisons between behavior and physiology of these foxes and those foxes bred for tameness. An important component of this comparative work would be measuring the levels of hormones in the two populations, with a focus on the stress-related hormones, which Dmitri and Lyudmila were sure were involved in some way with the foxes becoming tamer. Lyudmila had been able to take the blood samples only on occasion at Lesnoi because sampling required the help of workers to hold the foxes while she and her assistants drew the blood. Now she could do so regularly. This difficult and time-consuming sampling would soon produce rich rewards.
Another bonus of the experimental farm was that Belyaev could finally get to know the foxes intimately too, and he visited the farm as often as he could, sometimes even if he could only sneak away from the Institute for a few minutes with them. He especially loved watching the pups play out in their yards, seeing for himself the striking differences in the behavior of the tame pups versus the control pups. When he arrived, Lyudmila would sometimes bring a set of the tamest pups out so that he could see how they would lick his hands or roll over for him to pet their bellies. He was so enamored of the tame pups, marveling at how dog-like they were becoming, that he began imitating them when telling people about them, the way he acted out stories during dinners at his home with the staff. One of the researchers at the Institute recalls that “when he was talking about his foxes, changes would come over Belyaev, to his manners, to the way he was speaking, he behaved like a tame fox, he resembled a tame fox.” He’d curl up his wrists as if he were begging, smile and open his eyes as wide as possible mimicking the foxes’ excited reactions. The staff immensely enjoyed this because it showed a new part of him, what an animal lover he was.
Belyaev would occasionally bring visitors to the farm to show them the foxes, such as higher-ups in the Soviet Academy of Science or government officials on trips to Akademgorodok, and these people were also invariably charmed by the tame foxes. Lyudmila vividly recalls one such visit in particular. “I remember late in the evening after all the workers went home, Belyaev brought a famous army general, General Lukov, to the fox farm. I was given a heads-up that he was coming and that I must wait for the renowned guest.” Lukov was a formal man, with a military bearing hardened by years of service, including the horrors of the Soviet front in World War II. Yet, when Lyudmila opened a cage that housed one of the elite females, and the fox scampered right over to Lyudmila and laid down next to her, the General’s dignified demeanor melted away. “Lukov was astonished,” Lyudmila says. “He squatted near the fox and petted her head for a long time.” There was no denying that the tamest foxes were having a powerful emotional effect on people. And though the study of this effect was not a central component of the design of the experiment, they realized that it was a significant finding and might help to explain how domestication first started.
The rapid emergence of such solicitous behavior in some of the tame foxes fit well with Dmitri’s idea that the process of wolf domestication had been kicked off by the animals first becoming tamer. Now perhaps the experiment had produced an important clue about why the process would have escalated thereafter.
One long-standing idea about wolf domestication was that humans had adopted wolf pups, perhaps choosing ones that were especially cute, with the most juvenile facial and body features. But what if it were the wolves that initiated contact, not the humans? Naturally more adventurous when it comes to humans, tamer wolves might have begun making their way into human encampments to scavenge for food. Maybe, given that they’re nocturnal, they snuck into campsites in the night as our early ancestors slept. Or perhaps they had learned to closely follow human hunting parties to scavenge for prey. It’s easy to understand why wolves who were relatively comfortable with human presence–naturally semi-tame—would have done so. We were a much more reliable food source than the wild. But why had early human groups accepted the wolves into their inner sanctums? Wolves on their way to becoming dogs might well have helped with hunting and acted as sentinels, warning of approaching dangers. But there must have been earlier stages of their transition before they were performing these functions particularly well. If the process of the silver foxes’ domestication really was mimicking that of wolf domestication, then perhaps these same lovable solicitous behaviors emerged early on in wolves also. And maybe that made them more appealing to our early ancestors.8
But what would have driven the emergence of these behavioral changes in the wolves? Lyudmila was actively selecting the tamest foxes for mating. Is it plausible to believe that early humans would have actively mated wolves in a similar way? Perhaps they wouldn’t have needed to. Natural selection would likely have favored the wolves who had gained access to such a reliable, human-based food source. The wolves that were friendlier to humans might have found themselves living in close proximity with other such friendlier wolves who were hanging around humans, and they might have selected their own, semi-tame, kind as mates. That would have created the radically new selection pressure for tameness that the fox experiment was applying. And as Lyudmila and Belyaev were seeing with the foxes, this new selection pressure favoring tameness might have been enough to trigger the kinds of changes they were seeing in their tamest foxes. The process would have taken way longer than with Lyudmila’s artificial selection—as, indeed, it’s thought to have with wolves—but the same essential force might have been at play.
Dmitri and Lyudmila also realized that the early emergence of the endearing behaviors in their foxes might provide some important new perspective on the evolution of animal expressions, and perhaps even on the nature of animal emotions, which were hotly contested subjects at the time. The debate had raged for decades about whether animals feel anything like human emotion, and whether the behaviors of animals that appear to be expressions of emotion really are, or whether instead they’re simply automatic reflexes.
Charles Darwin was so fascinated by animal emotions that he made an extensive study of the subject, which he summarized in his classic book The Expression of the Emotions in Man and Animal. Published in 1872, the book was beautifully illustrated with drawings of animals’ expressions, which Darwin commissioned from a number of the leading animal illustrators of the day, such as of a cat arching its back and raising its tail to show affection, and a dog looking up in a submissive and affectionate pose.
Darwin thought many animals have rich emotional lives, and he argued that their emotions, and their thinking abilities, too, are on a continuum with those of humans. “The difference in mind between man and the higher animals, great as it is,” he wrote in The Descent of Man, “is certainly one of degree and not of kind.” Throughout The Expression of the Emotions, he showed great empathy toward animals and the intensity of emotion they can feel: “The appearance of dejection in young orangs and chimpanzees,” he wrote,” . . . is as plain and almost as pathetic as in the case of our children.”9 Many human expressions, too, Darwin argued, are instinctive. And to illustrate, he included a striking set of photographs of people displaying characteristic expressions, such as those of grief, surprise, and joy.
A SCHOOL OF ANIMAL BEHAVIOR RESEARCHERS who eventually followed in Darwin’s footsteps documented an astonishing array of complex innate behaviors, including, but not limited to, emotional behaviors. So compelling was the increasing evidence they produced of how genetically programmed animal behavior seemed to be that the idea that much of animal behavior was shaped by natural selection became the paradigm.
Generations of intrepid animal behaviorists had followed Leonid Krushinsky and others’ example of observing animals in the wild and headed out to forests, meadows, streams, and mountain ranges to conduct studies. Others began observing animals both in the wild and in captivity through inventive new techniques. Three men in particular—Konrad Lorenz, Karl von Frisch, and Nikolaas Tinbergen—did so much
to advance the understanding of animal behavior that they were jointly awarded the Nobel Prize in Physiology or Medicine in 1973. They carried out this work primarily in the 1930s, ’40s, and ’50s, and their fascinating findings were discussed often at both biology and psychology meetings.
The argument for natural selection as the driving force shaping animal behavior was strong. Many of the behaviors that Lorenz, von Frisch, and Tinbergen had observed generally conferred clear survival advantages. One of the most amazing of the elaborate behaviors observed was discovered by von Frisch, and performed by honeybees. Ingenious experiments he conducted with them revealed that they send signals to one another about where sources of nectar and pollen can be found when they return to their hives from foraging and perform a “waggle” dance.
Tinbergen observed remarkably complex and standardized behaviors in stickleback fish when it came time for mating. He discovered that the male always digs out a little crater of sand, which is almost always about two inches wide and two inches deep, and then covers it with a sticky wad of algae he forms from pulling bits together from the surrounding water into the crater. He then swims through this wad of algae to make a tunnel. Perhaps most amazing of all of is that he then changes color, from his normal bluish green to white on its back and a bright red on its underside. This is the trigger for a female to come mate, and when a female approaches, he directs her into the tunnel. She swims in, lays her eggs and leaves, and then he swims in and fertilizes them.10
For his part, Konrad Lorenz had caused a stir with his finding that Greylag goslings would treat him as their mother, becoming so attached to him that they waddled around behind him if he brought them out to a yard and walked around. Lorenz had noted how closely and rigorously goslings bonded to their mothers in the wild, never straying off and associating with other adult birds or with goslings other than their siblings. He was curious about this bonding process, and he performed an experiment in which he divided a group of freshly laid Greylag eggs in two, with one set being brooded over by the mother goose and cared for by her when they hatched and the other set placed in an incubator and cared for by Lorenz after they hatched. Those he had cared for became attached to him in just the way they would normally attach to their mother.
With more work, he discovered that there was a limited window of time during which this attachment formed. Whatever the goslings were exposed to during that window, they would treat as a parent, even if that was an inanimate object like a rubber ball. He concluded that the bond was formed instinctively, and he called the process imprinting. During this critical period in animals’ early development, their genetically determined behaviors could be dramatically altered by the conditions they were exposed to.11
What was fascinating about Lyudmila and Dmitri’s fox experiment results in relation to this work was that neither imprinting nor natural selection were the driving force behind the new behaviors or those that were retained beyond childhood in the tame foxes. Artificial selection for tameness was the driver. Exactly how, they did not know. But they were confident that Belyaev’s theory of destabilizing selection provided the answers about what was happening with the foxes. To prove it, they would have to gather a great deal more evidence.
The foxes would not let them down.
4
Dream
With the foxes moved into their roomier new home at the new farm, Lyudmila was delighted that she could give them exercise, and she had the caretakers let them out into the yards behind the sheds to run around for about half an hour every day. This gave Lyudmila a whole new category of observations to make—she could now watch them play.
When the pups were still small, from two to four months old, they were let out in small groups of three or four at a time, with no adults, so that things wouldn’t get too raucous. Just as with pups in the wild, who play with each other constantly when they’re not sleeping or feeding, the pups on the farm scampered exuberantly around chasing and pouncing on one another, nipping at each other’s tails and ears, and faux fighting by rolling around and wrestling with one another. Animal behaviorists refer to this kind of frisky roughhousing among animals as social play.
Many animals also engage in lots of play with inanimate objects, called object play, such as birds playing with twigs or shiny pieces of glass; cheetah cubs on the plains of the Serengeti who pat, carry, bite, or kick everything from bones to glass bottles; and dolphins playing with the air bubble rings they create. The tame fox pups threw themselves into this as well. Lyudmila bought them rubber balls, which they especially loved playing with, pushing them around with their snouts and jumping on them, but they had fun with anything they could get their little paws or mouths on, rocks, twigs, and some balloons also put out in the yards. As they got bigger and their jaws could open wide enough, they would pick the balls up in their mouths and race around the yard with them, trying to keep their prizes away from their brothers and sisters. This merging of social play with other pups and object play is also common in young animals, and is thought to help them develop the skills to keep a hold on their prizes from foraging or hunting that others in their own group would love to snatch away.
The adult foxes also played, and some of this was expected. Mothers in the wild play with their pups, and once in a while, Lyudmila observed them doing so and it pleased her greatly. Though social play between adults was rare in the elite foxes, they did engage in lots of object play with the balls and tin cans, and this was a big surprise. In the wild, adult foxes are preoccupied at almost all times with looking for food and avoiding predators. If an adult fox comes upon a novel object in the wild, it might smell the strange thing, or even paw it a little, trying to figure out what it is and whether it can be eaten. But that sort of exploratory behavior is quite different from what animal behaviorists categorize as object play, which continues after the animal has become familiar with an object and knows it’s not food.
This avid object play by the adult tame foxes was another way in which they were acting like pups longer, and also more like dogs, who love social and object play as both puppies and adults. Seeing the foxes out in the yard from a distance, one would have assumed they were some kind of smaller breed of huskies.
Lyudmila and the assistants from the Institute now working with her would often go into the yards to observe the fox pups playing up close, but they never attempted to interact with them at all, and they were careful never to interfere with their pups’ roughhousing. But some of the tame fox pups took the initiave and began involving Lyudmila and the assistants in their play routine, running up close to them with wagging tails, racing around them, and hiding behind their legs or nipping their shoes and bashfully running away. They seemed curious, and excited, about these tall beings in their midst.
Lyudmila had expected that observing the foxes play would be an important part of her work. The ways in which animals play had long been studied. Ornithologists had observed many types of bird play, such as when they hang upside down from tree branches and swing back and forth with apparent glee. Chimpanzees had been observed playing and chasing each other in ways that looked much like children playing tag. Even some insects had been observed to play. In 1929, August Forel, an influential ant researcher, wrote in his book The Social World of the Ants as Compared to Man: “On fine, calm days when they are feeling no hunger or any other cause of anxiety, certain ants entertain themselves with sham fights, without doing each other any harm; but these games come to an end directly [if] they are scared. This is one of their most amusing habits.”1 Today experts believe that these mock fights prepare ants for combat and courtship contests, which are key events in their lives.
Some observations suggest that animal play is, at times, a matter of pure enjoyment. Ravens in Alaska, northern Canada, and Russia are known to slide down steep, snow-covered roofs. When they reach the bottom, they walk or fly back to the top, and repeat the process over and over again. In Maine, ravens have been observed tumbling down small mounds of
snow, sometimes while holding sticks between their talons. Chimps living on the Mahale Mountains of Tanzania do something remarkably similar, and again for no discernable reason. Videotapes have captured them stopping as they walk down a mount, marching backwards and pulling a handful of leaves as they proceed. They then often stop and somersault through the pile in apparent joy.2 They seem to simply enjoy this play.
But play is also serious business, with many animal behaviorists arguing that it is essential for developing a host of social, physical, and psychological skills, preparing young animals for the challenges they will face as adults. Much social play is now thought to facilitate cooperation in groups of animals, such as when they’re hunting or defending themselves from predators, and also to teach the young where they are in the pecking order and who they’d likely beat in a fight versus who they’d better watch out for.
Parents often lead their young in play, as when older meerkats teach the young how to hunt.3 Juvenile kangaroos, called joeys, start play-fighting as soon as they leave their mother’s pouch, often seen sparring with their mothers. Their stylized boxing isn’t dangerous. Older partners self-handicap when they play with joeys by standing flat-booted and pawing, instead of throwing hard punches, teaching their little ones the finer art of sparring for when they will need it as they grow up, but sparing them the bumps and bruises.
Young ravens in nature manipulate and play with every object they encounter—leaves, twigs, pebbles, bottle caps, sea shells, glass fragments, and inedible berries—just as Lyudmila observed with the fox pups. Experiments in which Bernd Heinrich placed novel objects both in the field and in large aviaries show that this sort of object play by young ravens teaches them what is safe to eat when they are out foraging on their own as adults.4
How to Tame a Fox (and Build a Dog) Page 8
