from different population recruitments as well. Each adaptive locus/allele may have been independently selected in a different Fertile Crescent population and through time these combined, each allele contributing an increasingly additive effect, until their genomic consilience in an irrefutably domestic animal. Domestication in cats could thus be an allelic series of independently selected alleles from throughout the wildcat natural range, but assembled as a composite. In an analogous fashion, modern pig and cattle breeds are routinely “improved” via the introduction of advantageous alleles through crossbreeding distant strains (descended from independent Oriental and European domestications in pigs, and from European and Southeastern Asia in cattle), rather than by independent selection of each trait within each lineage.
At its most basic, domestication is a dependence on humans for food, shelter, and control of breeding (Price, 2002). Because 97% or more of the nearly 1 billion domestic cats living today are random-bred house cats, or are feral and intact, the overwhelming preponderance of domestic cats choose their own mates. Only a tiny fraction of cats (mostly those in registered breeds) have mates chosen for them (prezygotic selection). Furthermore, the majority of feral cats obtain what they eat without human assistance. Additionally, the domestic cat varies little morphologically from the wildcat body plan (Yamaguchi et al., 2004a,b), although, as Darwin noted, domestic cats have longer intestines than wildcats, a trait he attributed to a “less strictly carnivorous diet” as a result of feeding on kitchen scraps (Darwin, 1890). So an argument can be made that cat domestication is <200 years old and may yet be incomplete (Serpell, 1990). Domestic cats have, however, become polyestrous, and their coat colors often depart wildly from the wildcat’s striped mackerel tabby. And domestication did socialize the wildcat (cats are the only domesticate that is social under domestication yet solitary in the wild). However, the most noticeable adaptation is the cat’s overwhelming tolerance of people, a key attribute of any domesticated animal, but certainly the primary feature that has made cats the delightful and flourishing profiteers in our homes that they are.
The modern domestic cat is the product of 11 million years of natural selection in a world free of people (Johnson et al., 2006; O’Brien and Johnson, 2007), and 12,000 years of natural selection in a world increasingly dominated by humanity (Johnson et al., 2006; O’Brien and Johnson, 2007). In 1868, Darwin commented that there are no breeds of cats native to England because of a lack of selective breeding (Darwin, 1890, Vol. I,