Genomic Evolution of Our Feline Friends

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Cats are one of the most common domesticated animal on Earth, with an estimated 400 million worldwide. And yet they lack many characteristics that tended to make animals good for domestication. They are solitary hunters, making them relatively poor at responding to and valuing social hierarchies. So how exactly did early humans domesticate our feline friends? Recent research suggests stroking and treats may have been key to winning them over.

Cats were first domesticated around 9,000 – 10,000 years ago from the near eastern Wildcat (Felis silvestris lybica), which still roams the Middle East and northern Africa today. Cats first interacted with humans as they scavenged scraps of food from human settlements, but domesticating them can’t have been easy. The near eastern Wildcat is notoriously shy and solitary, hardly the ideal candidate for domestication. However, with the publication of the domestic cat genome this year, a few answers have begun to emerge. Cats were, it seems, domesticated primarily through rewards – food and petting.

Researchers at The Genome Institute, St Louis, generated the first full genome sequence of the domestic cat (Felis silvestris catus), and compared it to the genomes of the european Wildcat, the near eastern Wildcat and other domestic species including dogs and cattle. They found genetic changes in domesticated cats and dogs that adapted them to their new lives – improved fat metabolism to cope with a hypercarnivorous diet and heightened senses (primarily hearing and sight in cats and smell in dogs). The researchers also found several differences between wild and domestic cats that may offer clues into the process of domestication. In particular, domestic cats showed changes in genes involved in the reward centres of the brain and in the production of dopamine – the pleasure hormone. They also found changes in genes involved in fear conditioning and memory, probably also important in making cats more docile and trusting of humans.

So, it appears that humans domesticated cats by rewarding them – first with food, then with stroking, selecting for domestic cats that have increased pleasure responses. This process would not have actively discouraged the predatory nature of cats, however, which may explain why they continue to hunt no matter how much food we offer them. (A domestic cat kills between 30 and 50 birds a year, in the US, cats are responsible for killing 1.5 – 3.5 billion birds and 7 – 20 billion mammals every year!)

The neural crest hypothesis suggests that domestic and wild animals differ fundamentally in the development of their nervous systems, including their brains, resulting in a lack of fear and friendly characteristics that make them better companions for humans. This research provides the first data in support of the neural crest hypothesis, and reveals the deep effect of artificial selection on the genomes of domestic animals.

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Featured image copyright of Curiosity Photographic (2014), used with permission.

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