Evolution, Darwin thought, moved too slowly to observe on a human timescale. He was wrong. A few years after On the Origin of Species, William Dallinger started an experiment growing protozoa in an incubator. Over a number of years, he increased the temperature in the incubator from 15 °C/60 °F to 70 °C/158 °F. The original strain struggled at just a few degrees above baseline, but after years, the protozoa flourished at the higher temperature and couldn’t survive at 15 °C. Microbes reproduce quicker than larger organisms, and Dallinger concluded that he had observed evolution in action.
Since Dallinger, scientists have done a number of experiments with evolution in the lab. Potentially the most interesting, and certainly the cutest, is the domesticated silver fox experiment that has been going on for more than fifty years in Russia. The experiment was started in 1959 by Dmitry K. Belyaev, a geneticist who had lost his job some years earlier because his belief in Darwinism didn’t jive with the Lamarckian view of evolution prevailing in the Soviet Union at the time. Belyaev believed that the force behind the wide-ranging changes that occur when animals are domesticated was a single trait: friendliness to humans. Selecting for this trait, the project has created a fox that behaves like a dog. Although selected for behavior, the foxes also show morphological changes. Domesticated animals of diverse species show similar changes in physiology:
Belyaev believed that similarity in the patterns of these traits was the result of selection for amenability to domestication. Behavioral responses, he reasoned, are regulated by a fine balance between neurotransmitters and hormones at the level of the whole organism. The genes that control that balance occupy a high level in the hierarchical system of the genome. Even slight alterations in those regulatory genes can give rise to a wide network of changes in the developmental processes they govern. Thus, selecting animals for behavior may lead to other, far-reaching changes in the animals’ development. Because mammals from widely different taxonomic groups share similar regulatory mechanisms for hormones and neurochemistry, it is reasonable to believe that selecting them for similar behavior—tameness—should alter those mechanisms, and the developmental pathways they govern, in similar ways.
The project is funded partially by selling the foxes as pets. This research could not only help us understand domestication, but also shed some light on more general mechanisms that underlie social behavior. Perhaps some of the same mechanisms that help foxes or dogs socialize with humans may also be involved in autism. (Or perhaps not.)
Are domesticated foxes or dogs happier than their wild counterparts? On the one hand, the domesticated silver foxes live most of their lives in cages. On the other, they produce less of the stress hormone cortisol and more of the “happy neurotransmitter” serotonin. A domesticated life is significantly less stressful than a wild one, and this is reflected in their neurochemistry. Some of the foxes have been sold to fur breeders precisely because they suffer less in captivity. (Image: National Geographic.)