Geneticist who ‘turned foxes into dogs’

After reading Darwin’s The Variation of Animals and Plants Under Domestication, a study of how animals and plants have evolved through artificial selection, Belyaev had come to believe that the defining characteristic of a domesticated animal was its “tameness” and the experiment aimed, in essence, to fast-track the evolutionary process which had over centuries transformed wolves into dogs by selectively breeding for a particular trait: docility. “We have compressed into a few decades an ancient process that originally unfolded over thousands of years,” Trut said.

The project was larger in scale than any in the history of Russian genetics, which had previously stuck to viruses, bacteria and flies. Belyaev and Trut chose as their test animal the silver fox, a canny, elusive and often vicious variant of the red fox that had never before been domesticated. They were famous for their glossy silver coats and Trut sourced her patient zeros — some 140 silver foxes — from fur farms across the Soviet Union. To find the right location for the experiment she travelled on slow trains across vast stretches of the wintry country, disembarking at remote stations, usually deep in the forest, to visit commercial farms, all of which were owned by the state. She finally settled on a farm called Lesnoi, some 225 miles from Novosibirsk.

Trut with a domesticated Fox in 1974

SVETLANA ARGUTINSKAYA

It was fortunate that Lesnoi was so far from civilisation. The Fifties were a dangerous time to be a geneticist in the USSR and the team was working under the guise of increasing fur production. In the 1930s the pseudo-scientist Trofim Lysenko, who had risen up the ranks of the Communist Party by claiming to have invented a farming technique to triple crop yields, had initiated a widespread crackdown on the field of genetics. Stalin had branded genetics a “fascist science” and several researchers had been executed or thrown into prison camps.

In 1958 Lysenko created a committee and dispatched them to inspect the new institute in Siberia. “Committee members were snooping in the laboratories,” said Trut, and when the premier Nikita Khrushchev learnt of the committee’s unfavourable report he too paid them a visit. Khrushchev was “very discontented” and the experiment was only spared because his daughter, Rada, a well-respected journalist and biologist, believed Lysenko to be a charlatan. She reportedly convinced her father to keep it open.

Every year, Trut selected which foxes to breed by donning two-inch-thick protective gloves and placing a stick inside their cage, grading each fox’s reaction to her intrusion from one to four. “In the first years the vast majority of the foxes seemed less like dogs than like fire-breathing dragons,” she recalled. “I am sure these low scorers would have loved to rip my hand off.” The next generation seemed “to tolerate, but not enjoy, the presence of humans” but by the fourth and fifth the pups were wagging their tails as Trut approached. The sixth were whining, whimpering and licking her face, as a pet dog might do.

“The elites”, as Trut dubbed the 2 per cent that reacted in this way, appeared to “yearn for human companionship”. By 2017 that figure stood at about 70 per cent. “The elites charmed every human they met, no matter how toughened,” she recalled. “One evening after the staff went home, Belyaev brought a famous army officer, a General Lukov, to our facility. Lukov was a formal man, hardened by the horrors of war. But when I opened a cage that housed one of the elite females and the fox scampered over and laid down next to me, the general’s dignified demeanour melted away.”

Trut and Belyaev were able to show that the foxes responded to fear in a different way by measuring a steady decline in the hormone-producing adrenal gland, the flight or flight hormone, as well as an increase in serotonin — sometimes called the “happiness hormone”.

As she recalled in How to Tame a Fox (and Build a Dog), published in 2017, the physical appearance of the foxes also changed in what we now know as “domestication syndrome”. The camouflage coat of the wild foxes morphed into piebald splotches of white fur; their eyes were floppy instead of straight; they had shorter legs, curlier tails and more blunted snouts — and their faces were rounder. Their sex lives had also transformed: while wild female foxes had sex about once a year, tamer ones were more promiscuous. “Before our eyes,” Trut said, “the ‘Beast’ has turned into ‘Beauty’, as the aggressive behaviour of our herd’s wild progenitors entirely disappeared.’’

To prove that the changes were genetic, Trut and Belyaev developed a test in which they moved embryos from a group of tame mothers into the wombs of another group of more aggressive foxes they had developed — “what we thought of as a fox equivalent of Cerberus, the multiheaded hound of Hades that guards the gates of the Underworld. These were mean foxes.” The pups behaved like their biological rather than surrogate mother, proving that the changes were indeed inherited.

By 1974 most of the tame foxes had fallen into the “elite” category and to test further the bond that had developed between humans and the foxes, Trut suggested that she move into the small house on the farm with a fox called Pushinka (Russian for “a tiny ball of fuzz”), who was heavily pregnant. “In one of her favourite games I would hide a treat in my pocket, and she would try to snatch it out,” Trut recalled. “Sometimes she would lie on her back, inviting me to pet her exposed belly.” When Pushinka gave birth, she carried one of her pups over and laid it at Trut’s feet; Trut would “play ball” with the pups and “if I popped out of the house for a bit, Pushinka would sometimes sit at the window, looking out in anticipation of my return”.

Such canine devotion was nothing new. Born just outside Moscow in 1933, Lyudmila Nikolayevna Trut was raised by a dog-loving mother who during the Second World War, when food was scarce, would feed the starving stray dogs and tell her daughter: “If we don’t feed them, Lyudmila, how will they survive? They need people.”

Lyudmila took her mother along when she moved to Siberia, as well as her husband, Volodya, an aviation mechanic, and their baby daughter Marina. She spent most of her time alone in unheated sheds with the foxes in temperatures that regularly dipped below minus 40C, and she was often lonely. Yet she loved the work and never wanted to leave, even when she continued alone after Belayaev died in 1985 — or when, after the collapse of the Soviet Union four years later, most of their funding dried up. They were eventually forced to sell some of the foxes to Scandinavian fur breeders or as exotic house pets. By 1999 there were only some 100 females and 30 males left.

She was proud to have pioneered what is seen as one of the most ambitious long-term biological studies attempted. “As I look back on the experiment to which I have devoted three quarters of my life,” she wrote in 2017, “my thoughts sometimes drift to Antoine de Saint-Exupéry’s classic story The Little Prince and the fox’s admonition to the prince that “you become responsible forever for what you have tamed”.

Lyudmila Trut, geneticist, was born on November 6, 1933. She died on October 9, 2024, aged 90