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Rat: Man’s New Best Friend

December 28, 2012
Image Credit: photolinc / Shutterstock

Alan McStravick for redOrbit.com — Your Universe Online

The dog has been caught unaware by a competitor for man´s affections. And sure, the dog has a strong foothold on its title of ℠Man´s Best Friend´. But this new species angling for the position of top dog and the surreptitious behavior it displays in doing so can only lead one to surmise that this animal is acting, well, like a rat.

The reason one might perceive the rat´s march toward domesticity as particularly insidious is the brevity of time that has been required to get them to the point of docile coexistence with their human handlers when compared to our loyal canine counterparts. Of course, one component to their accelerated acceptance by and of humans has to do with the fact that we were instrumental in the unnatural selection that led to their eventual taming.

On the other hand, it has been hypothesized that the dog, responsible for their own domestication, required thousands of years to warm to their new best friends. Biologist Raymond Coppinger, who has spent over 45 years working with and studying dogs, postulates the taming process of the gray wolf began at the end of the last Ice Age, some 15,000 years ago. Coppinger states humans began, at this time, to gather and live together in what was the pre-cursor to our modern community style of living. He goes on to cite the fossil evidence of dogs, as we now know them, and their proximity to these primitive villages.

“People are organized into continuous settlements — villages where they remain for a long period of time, whether [they] were sitting on the edge of a shell fishery or on the edge of a coral reef. When humans live in the same spot for a long period of time, they create waste, including both sewage and, more importantly for the dog, leftovers. There are things people can´t eat, seeds that fall on the ground, things that have gone bad,” according to Coppinger. “The garbage, which might be found in dumps, or just scattered near houses, attracts scavengers: cockroaches, pigeons, rats, jackals — and wolves.”

It is the idea of “flight distance” according to Coppinger that helped in the transformation of the wild gray wolf to the modern incarnation that is today man´s best friend. “Flight distance” is a representation of how close any animal will allow humans to get before it runs away. The behavioral trait of a shorter flight distance was able, according to Coppinger, to be passed on from generation to generation, finally allowing the gray wolf to become the domesticated animal that was finally able to exist in comfort around humans.

So why is it the rat has been able to hone in on this, the sacred territory of the dog? To answer that question, we have to travel back to Soviet Russia in the 1950´s. The central planning model employed, it could have been argued, either streamlined or stifled the marketplace of ideas. And it was not limited to only the commercial, agricultural and military concerns that were the largest drivers of the national economy. Academia was witness to entire schools of thought being completely discounted in favor of another idea. Once the state had decided on a direction for study to continue, it was not only forbidden to explore other, competing ideas, it was often both professionally and personally dangerous.

One such idea, that of Mendelian genetics, which had been and continues today to be the basis of all genetic study, was summarily dismissed by Trofim Denisovich Lysenko, a Soviet biologist and agronomist who had devised his own, albeit false, study of what he termed vernalization. Vernalization was a method of agriculture that, according to Lysenko, required no minerals or fertilizers for plant growth and that could, through successive breeding, be passed down genetically from seed generation to seed generation. Despite a series of tragic famines that plagued the Soviet state and its satellites as a result of this flawed, even false philosophy, Lysenko was hailed as a hero of the state and maintained his dictatorship over Soviet science until the mid- to late 1960´s.

His “socialist genetics” was a blatant attempt at politicizing science and immediately drew the attention of the man that would become Lysenko´s greatest patron, then Soviet dictator Josef Stalin. With Stalin on his side, many who would dare oppose him would find their study defunded and themselves on a long train to a cold gulag.

Not many had the courage to oppose Lysenko outright. This was the case for the brothers Belyaev. Dmitry Belyaev and his brother were proponents of Mendelian genetics despite the iron fist Lysenko held around the throat of the school of thought he referred to as “alien foreign bourgeois biology.” And they each paid a price for their obstinate need to follow truth. Dmitry´s brother was sent to one of the above mentioned gulag´s where he lived until he died. Dmitry, on the other hand, was allowed to move to Siberia where he, in 1958, became the director of the Institute of Cytology and Genetics in Novosibirsk. This banishment from the central Soviet science structure actually emboldened Belyaev to seize upon his newly found academic freedom, zeroing in on the genetics of domestication.

So it was, in 1959, Belyaev began selecting many animal species for his domestication studies, among them the rat. Belyaev would select specific animals for his test colony based on its apparent tameness. The goal, as Belyaev saw it, was to cross-breed these tame animals to effectively produce a domesticated version of the species. To establish legitimacy for his studies, Belyaev also selected and cross-bred the particularly wild members of these species to produce supremely aggressive animals. Quoted in a July, 2006 New York Times article, Dr. Tecumseh Fitch of the University of St. Andrews in Scotland, and himself an expert on animal behavior, stated, “The audacity of this experiment is difficult to overestimate. The selection process on dogs, horses, cattle or other species had occurred, mostly unconsciously, over thousands of years, and the idea that Belyaev´s experiment might succeed in a human lifetime must have seemed bold indeed.”

The success of Belyaev and subsequent researchers and scientists cannot, however, be overstated. On that little farm just outside of Novosibirsk are colonies of domesticated fox, river otter, mink and even rat. And the work isn´t done yet. These studies and experiments have continued for over 50 years. In the scope of genetic time, that is but a blip. And yet, in so short a span of time, there have been produced species of animals docile enough that one might not even think twice about bringing one of these adorable animals home for their children.

After the fall of the Soviet Union in 1991, the progress of science and, more importantly, the funding of that science were definitely in question. But with the fall of the iron curtain also came a more open relationship with the international scientific community. Belyaev´s, and by extension, his successor, Lyudmila Trut´s research remained somewhat unknown until Trut published an article in 1999 detailing the 40 years of experimentation that had been undertaken in Novosibirsk. The attention gained opened up several avenues for scientific cooperation. It was through one of these outreach opportunities that some of Belyaev´s domesticated (and not so domesticated) rats were transplanted to the Max Planck Institute in Leipzig, Germany in 2004.

Dr. Svante Pääbo, PhD, director of the Department of Genetics at the Max Planck Institute (MPI) for Evolutionary Anthropology has maintained his study of the tame and aggressive Siberian rats for the past 9 years in the hopes of learning which genetic differences might exist between the two strains of the same rat. Pääbo, who had visited the Siberian refuge several times reflected on the eventual transfer, recalling, “It looked as if it would not work for a long time, but in the end we managed to build enough trust [with the Novosibirsk researchers].” Working with Dr. Pääbo at MPI is PhD candidate Alex Cagan.

Earlier this month at the Wellcome Trust´s ℠Rat Genomics and Models´ scientific conference hosted at the The Møller Centre at Cambridge University in Cambridge, England, Cagan offered insight into current study being done at MPI in a presentation entitled ℠Identification of Causal Genomic Loci in Rats Selected For Tame and Aggressive Behaviour´. Cagan, sighting previous studies that had helped to narrow the quantitative trait loci (QTL) down to 5 genomic loci, stated these loci, though significantly more precise than had been previously known, were still loci that each, themselves, were comprised of many genes. His work at MPI is hoping to narrow that field further by examining whole-genome sequence data from 20 rats. From this data of the tame and aggressive rats they will hope to find vastly divergent haplotypic homozygosity pointing to, what they believe, will be a genetic marker differentiating the behaviors of tame and aggressive animals.

Attending the conference on behalf of redOrbit, I had the opportunity to sit down with Cagan shortly after his presentation. One aspect of the research being conducted at MPI deals specifically with the MC2R which is the melanocortin 2 receptor. The significance of MC2R in the genetics of domestication, while still conjecture, is the widely held belief that it plays an important role in domestication. As Cagan explains, “There often has been the suggestion of a correlation between pigmentation and behavior, such as aggression.” An example of this he cites is an animal that is native to England. A black form of squirrel that has a higher concentration of melanocortins, and thus, darker pigmentation in their hairs, is more aggressive than its lighter haired grey squirrel cousins. While the exact link has not been established, the behavior of the black squirrel certainly seems to support Cagan’s and other geneticists hypothesis, in this regard.

“It suggests, because the melanocortin receptors not only have an influence on the pigmentation but can also have involvement in the brain or in the adrenal gland, receiving different hormones,” states Cagan. “And so by modifying this one pathway, you could be changing the pigmentation pathway and at the same time be influencing the behavioral pathways. And because we have noticed in domestic animals, they also have changes in pigmentation that it could be that this selection for the behavioral difference in making them tame has affected these receptors and is also having this knock-on effect on pigmentation, as well.”

The most interesting advancement discussed by Cagan had to do with a specific candidate gene that he believes will help to unlock researcher´s ability to understand behaviors in animals. As he explains, “What is positive selection acting on? If you are selecting for behavior, do you change the shape of the synapse? How fast it activates? Or even if it´s not something brain related. It could be hormone related. What´s kind of the best way for nature to change an animal´s behavior? If you want to change a specific behavioral response without messing around with all the other processes going on in the brain it might make sense for selection to play around with neurregulators, such as hormones, that can modulate behavioral responses without damaging orchanging the underlying architecture of the brain.” The specifics behind the candidate gene Cagan has identified will be published in 2013, preceding the completion of his doctoral studies.

Next on the horizon for Cagan is a mid-March journey to Novosibirsk to meet with his Russian collaborators. While he will surely take time to visit the original colonies of tame and aggressive rats from which his own studies were originally derived, the Siberian mission will begin another huge undertaking for this ambitious geneticist. Cagan will be taking samples from the mink populations to start the daunting process of mapping the as-yet-unknown mink genome.

From research that began only 54 years ago we have seen the quick and steady march toward domestication of the rat. With the research still continuing, it is interesting to wonder just how far the already cuddly and affectionate animals will proceed on this path. It seems these creatures could one day be both literally and figuratively nipping at the heels of our loyal four-legged friends. And it´s nice to know they have been teaching us a lot about themselves and us along the way.


Source: Alan McStravick for redOrbit.com – Your Universe Online



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