From wild animals to domestic pets, an evolutionary view of domestication

Abstract

Artificial selection is the selection of advantageous natural variation for human ends and is the mechanism by which most domestic species evolved. Most domesticates have their origin in one of a few historic centers of domestication as farm animals. Two notable exceptions are cats and dogs. Wolf domestication was initiated late in the Mesolithic when humans were nomadic hunter-gatherers. Those wolves less afraid of humans scavenged nomadic hunting camps and over time developed utility, initially as guards warning of approaching animals or other nomadic bands and soon thereafter as hunters, an attribute tuned by artificial selection. The first domestic cats had limited utility and initiated their domestication among the earliest agricultural Neolithic settlements in the Near East. Wildcat domestication occurred through a self-selective process in which behavioral reproductive isolation evolved as a correlated character of assortative mating coupled to habitat choice for urban environments. Eurasian wildcats initiated domestication and their evolution to companion animals was initially a process of natural, rather than artificial, selection over time driven during their sympatry with forbear wildcats.

Fig. 1.

Map of the Near East indicating the Fertile Crescent (according to ref. 23). Shaded areas indicate the approximate areas of domestication of pig, cattle, sheep, and goats with dates of initial domestication in calibrated years B.P. (after ref. 3). Colored lines enclose the wild ranges of Einkorn wheat, emmer wheat, and barley (after ref. 21). Green-shaded area in southern Levant indicates the region where all 3 grains were first domesticated 12,000 years B.P.

Fig. 2.

Distribution of F. Silvestris microsattelite and mitochondrial genotypes with associated dendrograms. (A) Shaded regions on map reflect the distribution of different STR genotype clades. mtDNA haplotype frequencies are indicated in pie charts specifying the number of specimens carrying each mtDNA haplotype clade. Domestic cats, F. silvestris catus are distributed worldwide and overwhelmingly carry clade IV mtDNA haplotypes (beige, see B below). (B) Minimum evolution/neighbor-joining phylogram of 2,604 bp of the ND5 and ND6 gene of 176 mitochondrial haplotypes discerned from 742 specimens sampled across the range of the wildcat (from Europe, Asia, and Africa), Chinese mountain cat, domestic cat, and sand cat. Genetic distance estimators (see ref. for details) provided concordant topologies that specified 6 clusters corresponding to the following subspecies designations: (1) F. silvestris silvestris wildcats from Europe (green, Clade I); (2) F. silvestris cafra wildcats from Southern Africa (blue, Clade II); (3) F. silvestris ornata wildcats from central Asia east of the Caspian Sea (purple, Clade III); (4) F. silvestris lybica wildcats from the Near East (beige, Clade IV); (5) F. silvestris bieti, Chinese mountain cats (red, Clade V); and (6) F. margarita, sand cat (black, Clade VI). The Chinese mountain cat is here referred to as a wildcat subspecies, F. silvestris bieti, as supported by data presented in ref. . The coalescence-based age of mtDNA ancestral nodes for all F. silvestris mtDNA lineages was estimated with the linearized tree method (58). The estimated age for the ancestor of F. silvestris lybica and domestic cats (clade IV) is 131,000 years. Other methods of date estimation suggested a range from 107,000 to 155,000 years (37). These estimates are all greater by an order of magnitude than archaeological evidence for cat domestication (39). The persistence within clade IV of 5 well supported mtDNA matrilines (A–E) dating back a hundred thousand years before any archaeological record of domestication indicates that domestic cats originated from at least 5 wildcat mtDNA haplotypes. (C) A phenogram (based on short tandem repeat (STR) data) for 851 domestic and wild specimens of Felis silvestris. Clade designations as in B.