Domestication of the Dog, Part I, The

Phi Kappa Phi Forum, Summer 2004 by Tiffany-Castiglioni, Evelyn

More puzzling is that dogs and wolves have nearly identical genetic material and identical chromosomes, and they can interbreed to produce fertile offspring, yet we classify them as different species. Indeed, all members of the dog genus - dogs, wolves, coyotes, and jackals, - have seventy-eight chromosomes and can interbreed to produce fertile offspring. The definition of species among animal behaviorists additionally includes the likelihood that groups of animals would naturally interbreed, which may be limited by geographical isolation, differences in social behavior, and the incongruity of their reproductive cycles.

The reasons that dogs and wolves generally live as different "species" are perhaps their very distinct habitats and behavioral characteristics. Wolves live in the wilderness in packs, have a hierarchy - one alpha male and one alpha female in a pack - and breed seasonally. In contrast, dogs live with humans and can breed more often. These behavioral differences, together with physical variations, have led scientists to classify dogs and wolves into different species. Under discussion is the idea that dogs should be classified as a wolf subspecies, Cants lupus familiaris. The analysis of the dog genome is nearly complete. DNA-sequence data in the dog would perhaps be a good starting point to verify whether dogs and wolves are different species, or just different breeds, and indeed will help refine our concept of species.

IS THE DOG JUST A TAME WOLF WITH FLOPPY EARS?

If the wolf and dog are genetically similar, why not call a tame wolf a dog? There is a difference between taming an individual and domesticating a species. The Latin root of the word "domestic" is domus, or house. Domestication means cultivating through generations of selective breeding animals that live with humans and serve human purposes. On the part of the animal, it means adaptation to a captive environment by an accumulation of genetic changes spanning several generations. Domesticated species have the common characteristic that they are tolerant of humans and often dependent on them. Their "fight or flight" adrenal response in the presence of humans is muted.

A remarkable study of the Siberian silver fox (Vulpes vulpes) reenacts how domestication may have taken place. The study was initiated in the 1950s in Russia by Dr. Dmitri Belyaev and is being continued by Dr. Lyudmila N. Trut (American Scientist, Vol. 78, p. 160; 1999). The project started with thirty male and a hundred female foxes from commercial farm stock that had been bred for fur for more than fifty years. These animals were therefore tolerant of caging and isolation from other foxes, but they were very afraid of humans, difficult to handle, and therefore still wild foxes.

During a period of forty years, researchers selectively bred farm foxes for a single characteristic: friendliness to humans. Monthly, beginning at one month of age, the fox kit was tested for its reaction to an experimenter, who offered it food and attempted to pet or handle it. Animals were categorized at seven to eight months of age as Class III if they tried to bite or flee, Class II if they allowed themselves to be touched but were not friendly, and Class I if they were friendly with the experimenter. Only the tamest animals were bred, which even in 1999 was less than 5 percent of males and 20 percent of females. After six generations, a new class emerged, Class IE, the domestic elite, who sought out human attention, licked the experimenters' hands, and wagged their tails in a dog-like fashion. After twenty generations, 35 percent of the animals were Class IE, and after thirty-five generations this proportion rose to 70-80 percent. In all, the experiment has involved 45,000 foxes.