histories. Over time and space, multiple wildcat matrilines would have been incorporated into the domestic cat gene pool through the admixture of an initial domesticate with additional wild female conspecifics, thereby spreading genes for the domestic phenotype through the early Fertile Crescent agricultural area. Thus, the relatively profound depth (131,000 years) of the catus/lybica clade may be best explained by a protracted wildcat domestication process that spanned thousands of years and extended over much of the Fertile Crescent (Fig. 5.1). The alternative hypothesis—of multiple independent domestication events—seems unlikely for 2 reasons: First, the vast majority of sampled domestic cats fall into the same mtDNA clade, which also includes F. silvestris lybica; and second, the clade lacks biogeographic structure. Individual house cats from any one sampling area may fall into any lineage, and even the most genetically divergent lineages have domestic individuals from the same sampling area. An important validation of this hypothesis awaits the identification of the causal mutations mediating domestic behavior in cats. Finding different mutations for the tame phenotype would suggest the multiple independent invention of domestication in cats, whereas finding the identical mutation(s) in all 5 domestic cat lineages would support a single origin for the gene complex spread by population diffusion.
Taken together, these results provide both phylogenetic and phylogeographic evidence that the divergence of domestic cat from wildcat occurred sympatrically. First, with respect to phylogeny, the monophyly of distinct taxa from the same environment (domestic cat and wildcat from the Near East) (Fig. 5.2B and C) is clearly consistent with sympatric divergence. Second, with respect to a phylogeography, sympatric divergence seems plausible because domestic cat and Near Eastern wildcat are phenotypically divergent (in terms of behavior) yet are more closely related to one another than Near Eastern wildcat are to more phenotypically similar allopatric groups (such as Asiatic wildcat or Southern African wildcat) (Fig. 5.2A). This scenario supposes a model of sympatric habitatrace formation in which habitat-specific beneficial mutations accumulated by assortative mating into a coherent allelic series. Importantly, this model avoids the “selection-recombination antagonism” described by Felsenstein (1981), whereby genes required for mating and genes required for assortative mating must be linked, because the same genes that drive habitat choice also drive assortative mating [see Via (2001) for review].
It seems likely that behavioral genes affecting domestication were initially selected by habitat choice of individual wildcats better fit for urban life, and that these genes were later transferred to geographically disparate spots, promoted by a human preference for tameness and perhaps the translocation of these individuals. However, it is also possible that individual component polygenes contributing to domestication derive