Chapter 2: Belyaev's Amazing Experiment

DNA is a molecule in living things. It affects the way animals look and behave. Like all kinds of evolution, domestication changes a species’ DNA. These changes can alter animals' size, fur colour, or tail shape . They can also alter how animals behave around people.

Russian scientist Dmitri Belyaev believed that behaviour was the most important difference between wolves and dogs. After all, wolves avoid people, but dogs want to lick peoples’ faces. To find out how domestication changes behaviour, Belyaev designed an amazing experiment.

Dog domestication took thousands of years. Belyaev would try to speed up this process. He would try to turn wild red foxes into tame ones. If it worked, scientists could watch as changes occurred.  They could use these special foxes to understand communication.

To learn about dogs, it made sense to study foxes. They are both part of the canine family, so they have a lot in common. Belyaev believed that meant the foxes, if domesticated, would be similar to dogs.

         Belyaev's second reason was that red foxes already lived around people. In Russia, foxes were raised and sold for their valuable fur. But these foxes were not tame. People could not touch them without danger of being bitten. The foxes lived on farms, but their behaviour was wild.

The Experiment Begins

In 1959, Belyaev's team of scientists bought 130 farm foxes to start the experiment. Each fox had its own wire cage at the Institute of Cytology and Genetics in Siberia, Russia. The scientists were not allowed to pet the foxes or train them. Training changes an animal’s behaviour. To study domestication, Belyaev's team needed to see DNA changes only. Training would ruin the experiment. 

To measure behaviour, the scientists tested the foxes’ reactions to people. They needed to answer several questions. Did the fox stand at the front of its cage, or did it hide at the back? Did the fox growl or snarl? Were its ears relaxed, or pinned to the side of its head? Would the fox let people touch it, or try to bite? The team took notes on each of the foxes. The notes showed how wild foxes behaved at the beginning of the experiment.

Belyaev’s team chose the tamest foxes for breeding. Only one fox out of every ten was chosen. After the foxes mated, they had puppies. The scientists tested how the puppies behaved around people. Then the breeding cycle started again.

Becoming Tame

The results were surprising. Fox behaviour changed much faster than scientists expected. After just three rounds of breeding, fox puppies stopped trying to attack people. After four rounds, a fox puppy wagged its tail like a happy dog. No fox had ever wagged at a person before.

Today, after 50 years of breeding, the wild foxes have become domesticated. When domestic foxes see people, they whine and wiggle for attention. They nibble people’s fingers and slurp people’s faces. They take walks on leashes and come when they’re called. Puppies do these things when they’re just three weeks old, too young to know very much about people. Team member Anna Kukekova says, “They remind me a lot of golden retrievers, who are basically not aware that there are good people, bad people, people that they have met before, and those they haven’t.”

The foxes’ DNA had changed. The next step was to see if the foxes could talk.

 [sidebar] Red Foxes

Wild red foxes live in more places than almost any other land animal. They are found in Canada, the United States, northern Asia, and most o fEurope. Despite their name, not all red foxes have red fur. About 10 percent have dark grey or black fur, and some are even white.

[sidebar] Domestic or Trained?

Circus lions and animal actors are trained to be gentle around people. But training does not change their DNA, so their babies are still wild. Domestic animals have different DNA than their wild ancestors. Their babies will also be domestic.

[sidebar] Learning Fear

When animals are born, they cannot feel fear. They learn to be afraid of new things as they grow. Fear helps them avoid dangers in the wild.

            Wolves and wild foxes learn fear when they are one-and-a-half months old. Domestic foxes don’t learn fear until they are four months old. Dogs take up to six months. Scientists call the time before fear the socialization period. It is longer in domestic animals than in wild ones. This gives domestic animals extra time to learn that people can be part of their packs.

 [callout 3] By 2009, around 50,000 foxes had been born as part of Belyaev’s experiment.

The Opposite of Domestic

In 1970, Belyaev’s team began a second experiment. Instead of picking wild foxes that were tame around people, they bred the meanest, angriest foxes they could find. The descendants of these foxes snarl and snap. Even their puppies try to attack people. These aggressive foxes are the opposite of domestic.

The scientists wondered if fox mothers taught their babies to be mean. They took domestic and aggressive fox mothers and switched their puppies. Domestic puppies raised by aggressive mothers grew up tame. Aggressive puppies raised by domestic mothers grew up mean. This proved that foxes do not learn how to act from their mothers. Instead, their DNA causes their behaviour.