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Hundreds of millions of cats are kept as pets around the world. Cats have either a mutualistic or commensal relationship with humans. Cats are also used in the fur trade, as food, and to control pests. Cats and humans evolutionarily diverged from a common ancestor (boreoeutherian ancestor) approximately 80 million years ago, accumulating only 10–12 chromosomal translocations. The order of several genes in chromosomes X and Y in cats closely resembles that in humans. ==Pet== Cats are common pets in all continents of the world, and their global population is difficult to ascertain, with estimates ranging from anywhere between 200 million to 600 million.〔(【引用サイトリンク】url=http://www.ifaheurope.org/companion-animals/about-pets.html )〕〔(【引用サイトリンク】url=http://www.ncbi.nlm.nih.gov/pubmed/3101986 )〕〔(【引用サイトリンク】url=http://english.pravda.ru/society/family/09-01-2006/9478-cats-0/ )〕〔(【引用サイトリンク】url=http://www.nytimes.com/2007/06/29/science/29cat.html?_r=1& )〕 In 1998 there were around 76 million cats in Europe, 7 million in Japan and 3 million in Australia. A 2007 report stated that about 37 million US households owned cats, with an average of 2.2 cats per household giving a total population of around 82 million; in contrast, there are about 72 million pet dogs in that country.〔(【引用サイトリンク】title=Market Research Statistics – U.S. Pet Ownership )〕 Cats exceeded dogs in number as pets in the United States in 1985 for the first time, in part because the development of kitty litter in the mid-20th century eliminated the unpleasantly powerful smell of cat urine. Although cat ownership has commonly been associated with women, a 2007 Gallup poll reported that men and women were equally likely to own a cat. The ratio of pedigree/purebred cats to random-bred cats varies from country to country. However, generally speaking, purebreds are less than 10% of the total population. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Human interaction with cats」の詳細全文を読む スポンサード リンク
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