When I get home from work, I like to play with my old dog, Buster Brown. Despite his membership in the canine branch of the AARP, Buster still likes to play like a puppy.
People have long speculated about how the ancestors of dogs – wolves – were coaxed into a partnership with us that markedly changed both their looks and behavior. One interesting long-term study done on foxes in Russia speaks to at least part of the puzzle of how wolves who won’t tolerate our company became dogs who are happy to play with us throughout their lives.
The fox research hinges on the work of Dmitry Belyaev, a scientist who bred foxes over many generations starting in the late 1950s. Generation after generation, Belyaev selected the most tame of the foxes he had living in cages to breed with each other. Now some of the foxes in this long-running experiment act pretty much like domestic dogs, showing excitement rather than fear when approached by a human and wagging their tails at people.
I was reminded of Belyaev’s work by the publication recently of a further study on the foxes done by Cornell University’s Lenore Pipes. Her results were presented at the Biology of Genomes conference and reported by the ScienceNews website.
The tame behavior of Belyaev’s interesting foxes must be related at some level to genetics, but researchers have not found simple differences in DNA that can explain the changes in the animals’ behavior. So Pipes and her colleagues looked for differences in the activity of genes in certain parts of the foxes’ brains.
Pipes and her co-workers took two sections of the brains from a dozen tame foxes and a dozen of the most aggressive foxes also bred in captivity. The sections of the brains at issue were the prefrontal cortex and the amygdala. The researchers found that the activity of many genes in those brain regions differed in the tame foxes versus the most aggressive ones. Score one for leading-edge science.
Although scientists are making impressive progress understanding animal brains and those of humans, we still have a lot to learn. Pipes and her colleagues focused part of their work on serotonin, the chemical in brains thought to be low in people with depression. Several common antidepressant medications help boost the activity of serotonin. It’s a fact that tame foxes have more serotonin in their noggins than wild-type foxes do. Piper and her team had expected to find changes in the genes that influence serotonin levels. But only one gene appears to be related to that, far fewer than the many genes at issue in the prefrontal cortex and amygdala.
It’s impressive how rapidly we can change animals and their behavior by choosing who gets to be the mamas and the papas of the next generation. But we don’t yet fathom how selective breeding makes for all the changes observed in foxes – and in animals like Buster Brown.