By comparing foxes selected for tameness with others that have not been selected in this way, researchers have found evidence that dramatic behavioral and physiological changes accompanying tameness may be associated with only limited changes in gene activity in the brain.
The work is reported by Elena Jazin and colleagues at Uppsala University, the Swedish University of Agricultural Sciences, and the Norwegian University of Life Science.
The first step in the process of domestication in mammals is the selection for tame individuals that can adapt to life with humans and to frequent handling. To investigate the changes in gene activity that accompany tameness, in the present study the authors compared two groups of farm-raised silver foxes (Vulpes vulpes). One group derived from a long-standing domestication process in which farm-raised silver foxes have been selected for more than 40 generations for non-aggressive behavior toward men (see the related work of Brian Hare and colleagues, Current Biology 15:226–230). Another group of foxes was also farm raised but was not selected for tameness. The foxes selected for tameness were docile and friendly and showed developmental, morphological, and neurochemical changes similar to those observed in other domestic animals.
To examine what genetic and molecular mechanisms underlie these dramatic changes, the researchers studied the activities of thousands of genes in the brain of selected and non-selected silver foxes and compared the activity of these genes with that of genes in the brains of wild foxes.
The researchers found that although there were many differences in the gene-activity profiles of the wild and farm-raised foxes, foxes selected for tameness showed relatively limited changes in brain gene activity when they were compared to non-domesticated farm foxes. Because the selected and non-selected foxes live in an identical environment, the authors point out that the differences in gene activities that do exist between these two groups probably reflect the consequences of behavioral changes accompanying tameness, whereas the differences between wild and farm-raised foxes likely derive from other factors, including adaptations by farmed foxes to life in a captive environment. Taken together, the findings support the hypothesis that genetic changes influencing the activity of genes expressed in the brain may act as an important mechanism for evolutionary behavioral alterations that arise in the course of domestication.
Cell Press. November 2005.