In 2003, while the geneticist Svante Pääbo was visiting Novosibirsk, Russia's third-largest city, he decided to look in on a famous experiment run by the Institute of Cytology and Genetics, which is based in the city. Fifty years ago, the then head of the institute, the geneticist Dmitry Belyaev, had begun breeding silver foxes to see how easily they could be tamed. What Dr Pääbo did not know, though, is that Belyaev had also set up another experiment in the 1970s involving rats. This time, one line of rats was selected for tameness and another selected for aggression.
When Dr Pääbo saw them, he was stunned. After just 30 years of selection, the researchers had fashioned two populations that could hardly be more different. "I could take the tame ones out of the cage with my bare hands. They would creep under my shirt and seemed to actually seek and enjoy contact," Dr Pääbo recalled. "The aggressive animals were so aggressive I got the feeling that 10 or 20 of them would probably kill me if they got out of the cages," he realised.
Here was a great opportunity to uncover the genetic changes responsible for the behavioural differences, Dr Pääbo realised. Back at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, Dr Pääbo and his team have been trying to do just this. If they succeed, their findings could have far-reaching consequences. Charles Darwin thought the process of domestication was "insensibly slow". But Belyaev thought otherwise. He proposed that many of the features typical of domesticated animals arose because our distant ancestors made their initial selection of wild animals on the basis of just one, rather practical characteristic: tameness.
In 1959, Belyaev set out to test his idea. He obtained 130 relatively friendly silver foxes from a fur farm in Estonia and installed them at a farm near the small town of Kainskaya Zaimka, on the outskirts of Novosibirsk. He began to breed them, but in each generation only allowed the very tamest animals to reproduce. Within four generations, some of the foxes had started to wag their tails; after eight generations new spots and markings began to appear on some of the offspring; then ears flopped, tails shortened, skulls widened and the foxes became more relaxed about when they bred. After just 20 years, Belyaev's team had created a domestic fox.
The silver fox is just one animal, though. Would selection for tameness bring about similar rapid changes in other mammals, too? It was to address this that Belyaev obtained a group of wild rats in 1972 and set about creating the two lineages. Next, Belyaev turned his attention to American mink. He approached a fur farm housing 30,000 animals and came away with 200 relatively tame individuals. After just four generations of selective breeding, there was clear evidence that domestication was under way. Not only were the animals easier to approach, but novel coat colours and other anatomical features had started to appear, just as they had done with the foxes.
Starting in 1980, the researchers began to capture wild river otters, bringing them to the farm from Sakhalin Island, north of Japan. Thirteen years and three generations later, the percentage of tame river otters at the farm had more than tripled, from around 10 per cent initially. These animals also had lighter markings, earlier reproduction and changes in brain chemistry. The results of these experiments suggest that Belyaev was right: far from the characteristic features of domesticated mammals requiring hundreds of generations of selective breeding, they start to appear in just a few. With all the animals, selecting for tameness brought with it new colour variants and altered reproduction, in fact pretty much all the features typical of a domesticated species. According to Lyudmila Trut, who took charge of the experiments after Belyaev's death in 1985, part of the reason is that breeding for tameness produces changes in the timing of developmental processes.
Confident that the differences in behaviour are due to gene variants, the researchers set out to find them. Their preliminary findings highlight several key regions of the genome that have a strong effect on tameness. The mission is now to home in on what these genes are and exactly what they do. If there are multiple mutations, each with a small effect on behaviour, this will be pretty challenging, said Leif Andersson, a geneticist at Uppsala University in Sweden involved in the project. "I am optimistic that we will be able to reveal the mutation and the gene underlying this major effect within a couple of years."
The same genes might turn out to underlie social behaviour in a wide range of mammals - including us. If there is a common genetic basis for domestication, the work of Dr Pääbo could make it much easier to domesticate other species. Take the African buffalo, for example. It is notoriously aggressive, killing more people each year than the lion. The benefits of creating a line of less volatile - even friendly - buffalo would be enormous.
Some people will object to the very notion of domesticating more wild species, whether for farms or as pets. But many tame animals, such as dogs, cats, horses, sheep, now far outnumber their wild relatives. Wouldn't it be better if some threatened animals survived as pets or farm animals rather than not at all? There is also a certain appeal to the idea of taming exotic creatures. Take zebras. While a few individuals have managed to ride them, they have never been fully tamed.
"Maybe we have not tried hard enough to find zebras that are suitable for domestication," Dr Andersson said. If Dr Pääbo's genetic quest reveals the secret to taming the zebra, Royal Ascot might never be the same again. New Scientist