Lyudmila Trut, who has died aged 90, was a Soviet scientist and lead researcher on the silver fox domestication study, one of the most significant biology experiments of the 20th century, compressing thousands of years of evolution into a single human lifetime.
After generations of selectively breeding only the tamest of these "fire-breathing dragons", as she put it, she found that the foxes had not only became as friendly as golden retrievers, they had also become more dog-like in appearance. The study was influential as a convincing analogy for how dogs might have emerged from early man's selective breeding of wolves, and in its striking demonstration of the principles of Darwin in action.
Begun in 1959, the experiment was the brainchild of Dmitry Belyaev, a disciple of Darwin and Mendel - ideas that had cost Belyaev his job in 1948 at the Institute for Fur Breeding Animals in Moscow when the genetics-denying charlatan Trofim Lysenko held sway over Soviet science.
Belyaev was gripped by a problem first spotted by Darwin: that domesticated species share a "suite" of characteristics, now known as "the domestication syndrome", including floppy ears; shorter, curlier tails; more juvenile-looking bodies; lower stress hormone levels; mottled or curly coats; and reproductive cycles that ceased to be coupled to the seasons.
These traits expressed themselves regardless of what that particular species had been domesticated for, whether cart-pulling, sheep-guarding, or milking - activities for which a floppy ear or a mottled coat did not seem to confer any particular advantage.
Belyaev's hypothesis was that all domesticated animals must, in the first instance, have been bred to be cooperative with humans, or "tame", before any other trait could be selectively bred; these diverse physical traits must therefore somehow be linked to the genes that code for tameness.
In 1958 the five-foot-tall, 25-year-old Lyudmila Trut was recruited as his lead researcher, and together they devised an experiment to replicate the earliest days of dog domestication, but using a canid that had never before been domesticated: the silver fox.
From fur farms they purchased 130 of the most docile foxes they could find, and at the new Institute of Cytology and Genetics in Novosibirsk, Siberia, started breeding from the calmest kits (babies). To hide from the Lysenkoists, the official aim of the study was to increase fur production.
After only six generations, the foxes were remarkably different: without any training, they would lick the hands of the scientists, whimper for affection and could be picked up and petted. By 1969, they had support for Belyaev's thesis about "domestic" physical traits when a fox called Mechta was born with droopy ears.
In due course, the foxes' bodies became more stocky - an attribute of juvenile wild foxes - and their muzzles shorter and rounder, often with a white star or other pigmentation, and their tails curly. Their stress hormone levels had halved, their adrenal glands had shrunk and their "happy hormone" serotonin levels had gone up.
Belyaev died in 1985, leaving Lyudmila Trut to carry on the project until the present day, yielding reams of useful data on genetics, and compressing "into a few decades an ancient process that originally unfolded over thousands of years," as she put it in Scientific American in 1999. "Before our eyes, 'the Beast' has turned into 'Beauty', as the aggressive behaviour of our herd's wild progenitors entirely disappeared."
In 2019, however, an article in Trends in Ecology and Evolution challenged whether the silver fox study had indeed proved the existence of "the domestication syndrome", arguing that the original foxes were already on the road to domestication, having been bought from fur farms. Others pointed out, however, that Lyudmila Trut had also tested two more lineages of foxes, one bred for aggression and another as a control; neither developed the curly tails or spots of the tame foxes.
Lyudmila Nikolayevna Trut was born on 6 November 1933 and brought up just outside Moscow. She shared "a pathological love for animals" with her mother, who during the Second World War, she recalled, would spare some of their scanty rations for the stray dogs.
Lyudmila studied physiology and animal behaviour at Moscow State University. With her husband Volodya, an aviation mechanic, their baby girl and her mother, she moved to Siberia to start Belyaev's experiment, which would involve over 45,000 foxes across six decades.
Lyudmila Trut kept the study going on a shoestring after fall of the Soviet Union and the late-1990s collapse of the rouble, but by 1999 only 100 tame females and 30 tame males were left alive. An article in Scientific American raised funds to keep the study going, but from 2010 she was resorting to selling foxes as exotic pets via a private company in Las Vegas for $6,950. Even so, each year hundreds of the foxes had to be euthanised or sold to fur farms to cover the costs of caring for the rest.
In 2019 she published, with Lee Alan Dugatkin, How to Tame a Fox (and Build a Dog).