Cats is based on T. S. Eliot's 1939 poetry book Old Possum's Book of Practical Cats, with the songs in the musical consisting of Eliot's verse set to music by Andrew Lloyd Webber. The musical is unusual in terms of its construction; along with Eliot's poems, music and dance are the main focus of the show at the expense of a traditional narrative structure. Musicologists William Everett and Paul Laird described Cats as "combining elements of the revue and concept musical". The plot centres on a tribe of cats called the Jellicles, as they come together at the annual Jellicle Ball to decide which one of them will ascend to the Heaviside Layer (their version of heaven) and be reborn into a new life. The bulk of the musical consists of the different contenders being introduced, either by themselves or by other cats.
Niacin is an essential vitamin for the cat; dietary deficiency can lead to anorexia, weight loss and an increase in body temperature. Biosynthesis of niacin occurs by metabolism of tryptophan via the kynurenine pathway to quinolinic acid, the niacin precursor. However, cats have a high activity of picolinic acid carboxylase, which converts one of the intermediates to picolinic acid instead of quinolinic acid. As a result, niacin can become deficient and require supplementation.
It was long thought that cat domestication was initiated in Egypt, because cats in ancient Egypt were venerated from around 3100 BC. However, the earliest indication for the taming of an African wildcat (F. lybica) was found in Cyprus, where a cat skeleton was excavated close by a human Neolithic grave dating to around 7500 BC. African wildcats were probably first domesticated in the Near East. The leopard cat (Prionailurus bengalensis) was tamed independently in China around 5500 BC, though this line of partially domesticated cats leaves no trace in the domestic cat populations of today.