Domestication through the Centuries: Darwin’s Ideas and Dmitry Belyaev’s Long-Term Experiment in Silver Foxes

Abstract

The problem of the origin of domestic animals and plants, and the means by which they were produced along human history, were of deep interest to Charles Darwin who considered domestic breeding ‘one grand experiment’ in evolution. In ?first place, he elaborated an analogy between arti?ficial selection, by which breeders obtained desired characters in domestic species, and natural selection, the powerful force driving evolution in nature. At the same time, Darwin distinguished two processes within arti?ficial selection: methodical and unconscious selection. He attached great importance to the latter since it could produce gradual unexpected changes in association with those characters that were consciously selected for. Although the analogy natural/arti?ficial selection was initially controversial, it proved to be extremely useful in establishing the reality of natural selection as a key evolutionary factor. Nevertheless, the mechanisms involved in the process of domestication were largely unknown and posed intriguing problems such as the recurrent morphological, physiological, and behavioural similarities that appeared in widely different domestic animals. A distinguished Russian geneticist, Dmitry K. Belyaev, proposed that domestication was ruled by a process of ‘destabilizing selection’ affecting mechanisms of ontogenetic neuroendocrine control, either directly or indirectly in response to the appearance of a factor of stress. He also suggested that the key factor of domestication producing striking similar results in many species is selection for tameness. Thus, in 1959 he set up a long-?term experiment of domestication of wild foxes (Vulpes vulpes) in which individuals were exclusively selected for tameness. Today, almost 50 generations later, near 100% of the experimental population actively seeks contact with humans. They exhibit a typical dog-like behaviour, which has been shown to be directly related to neuroendocrine ontogenetic modi?fications. Typical dog-?like morphological, physiological and reproductive characteristics also appeared in the domesticated foxes. In this essay I review Darwin’s ideas on domestication and then focus on Belyaev’s still ongoing experiment and the consequences of its results for the theory of domestication and evolution.