The Origin of the Dog Revisited

The most widely accepted hypothesis of the origin of the dog, Canis familiaris, is that the dog is a domesticated gray wolf, Canis lupus. This paper reviews the evidence for this conclusion, finds many unanswered questions and conceptual gaps in the wolf origin hypothesis, and explores the alternative hypothesis that the most likely ancestor of the domestic dog was a medium-size, generalist canid. Introduction Currently, there is a general consensus that the sole ancestral species of the domestic dog, Canis familiaris L. 1758, is the gray wolf, Canis lupus L. 1758 (Coppinger & Smith 1983; Clutton-Brock 1984, 1995; Olsen 1985; Wayne 1986; Tchernov & Horowitz 1991; Morey 1992; Wilson and Reeder 1993; Cohn 1997; Vilà et al.1997; Budiansky 1999; Crockford 2000; Coppinger & Coppinger 2001). However, there is at least one competing hypothesis that is equally plausible, yet has not been given adequate evaluation in the published literature. The dog origin alternatives are: (1) an origin from golden jackal (Canis aureus) (Lorenz 1954); (2) an origin from hybrids of wild canids (Darwin 1875; Clutton-Brock 1977; Brisbin 1997); or (3) an origin from a wild Canis other than jackal or C. lupus (Epstein 1971; Zeuner 1963; Fox 1973; Manwell & Baker 1983). Jackal ancestry of the domestic dog (hereafter DD) can be dismissed due to the large genetic distance separating the two (Wayne & O'Brien, 1987; Wayne et al., 1991a). Although a hybrid origin (e.g., Canis simensis or Cuon alpinus with small subspecies of C. lupus), suggested by several authors to account for the sudden shift from wolf to primitive dog morphology, cannot be ruled out, currently no direct evidence supports this hypothesis. In this paper, I review selected behavioral, morphological, molecular, and fossil information relative to the competing hypotheses of wolf origin and wild canid origin. Appendix I provides my working definitions of terms with variable meanings. Discussion Behavior Many hypothesize that the wolf was pre-adapted for domestication as it is one of the rare pack-living canids. Gregarious social structure facilitates domestication because humans manage domesticants through social domination (Clutton-Brock 1981, 1994, 1995; Olsen 1985; Hemmer 1990). However, wolf behavior has significant differences from the behavior of domesticated non-predatory species. Unlike most gregarious noncarnivore species, wolves are able to survive as individuals independent of the group and within the pack have diverse roles (Mech 1970; Sullivan 1978). With careful conditioning using modern methods, wolves can be tamed (Crisler 1958; Klinghammer & Goodman 1985), but not trained to follow commands reliably. Although they respect limits on inter-individual conduct, wolves resist human direction of their activities and