Home » Bone of the Month » A Look into Cat Genomics

A Look into Cat Genomics

Image of an Abyssinian cat. image taken from http://proxvost.info/ln/en/short-haired/abyssinian_cat.php

Image of an Abyssinian cat, the first to have their genome sequenced. Image taken from http://proxvost.info/ln/en/short-haired/abyssinian_cat.php

As a part of my Skull of the Month series I always try to find out a bit about the chosen animal’s evolutionary history. This is because I studied human evolution at university and want to broaden my knowledge of other animals. This month’s skull is the domestic cat, an animal I am familiar with in everyday terms but not on a scientific one.

Previously I have written about the domestic dog and their history. To be honest I already had a general idea about the dog’s past as I also have always had an interest in wolves. It is also evident that the domestication of dogs came about through hunting and guarding with human settlements.  The cat, however, is a completely different story. Of course I know that the domestic cat is related to the other big cats around the globe but that’s as far as it went and with regards to cat domestication I didn’t even know where to start! However, a quick search on Google Scholar identified the perfect article to start off with. This was a review article from Cell Press entitled ‘State of Cat Genomics’ by O’Brien et al. (2012). This article takes a look at some of the progresses made within the field of genomics relating to the domestic cat including how the genomes have been sequenced and what they can tell us about the evolutionary history and domestication of the humble cat.

The modern cat was selected as one of 24 mammals to have their entire genome sequenced in 2005 by the National Human Genome Research Institute. The first cat to have this done was an Abyssinian cat called Cinnamon. By examining genomes of other mammals advancement into human, and also animal, health can be made. Table 1. (p.269) in the article provides some examples of the used for cat genomes.

 In order to reconstruct the origins if the domestic cat a robust molecular phylogeny had to be made. To do this the 35 cat genes were selected and sequenced in all cat species. The earliest identified predecessor of cats lived in Europe during the Miocene and was Pseudaelurus andgave rise to the Asian ancestor of modern cats ~11 million years ago (Mya). The first split from this ancestor cat produced the Panthera genus (containing lions, tigers and leopards, around 10.8 Mya.  A second split in Asia produced more species which speciated and moved into South East Asia. A further split around 6-10 Mya produced an inter-continental migration into Africa. This was achieved by a fall in sea levels producing a land bridge across the Red Sea. This also occurred across the Bering Straits to Alaska permitting movement into these new continents. As sea levels raised these land bridges were lost which separated the continents allowing for evolution of new species of cat that we are familiar with today. During the Pliocene more migrations occurred between America and Asia and into South America as the sea levels continued to rise and fall over time.

Molecular phylogeny of Felidae. Image taken from article, fig. 2 p. 273.

Molecular phylogeny of Felidae. Image taken from article, fig. 2 p. 273.

 From the genetic data it has been established that the origins of cats was founded in Asia. However, where and when did the modern cat that is so familiar today come from? By conducting a phylogeographic study using a large data set of domestic and wildcats from Asia, Europe and Africa the evidence pointed to the Near East. It was found that a large proportion of domestic cats across the globe possess genotypes which are indistinguishable from classes that have been identified in subspecies of wildcats cats in the Near East. In addition to this a discreet population of wildcats was found in the Near East using an alternative analysis. This evidence suggests that the founding population for the world’s domestic cats came from this area.

 Aside from the genetic data archaeological remains also support the theory of the origins of cat domestication residing in the Near East. The remains for cats and humans were found together and dated to 9,500 years ago. This coincides with the first agricultural settlements in the Fertile Crescent, an area of fertile land between the Arabian desert and the mountains of Armenia.  These settlements also date to 10,000 years ago, providing compelling evidence that humans and cats were in the same place at the same time. 

 A theory as to why cat domestication arose is that the cats may have been used to farmers in the removal of rodents. It is known today that cats are sometimes bought and kept in order to rid mice and rats of land. However, in the late 18th, early 19th Century cats were started to be selectively bred to produce fancy breeds. This is in stark contrast to the domestic dog that was bred into a number of sizes and types to assist with hunting. Most importantly these cats can be traced back to those in the Near East. Interestingly all 68 breeds of the international Cat Association and the American Cat Fanciers can trace their origins to the Fertile Crescent and human civilisation. 

 From this one article I have already learnt so much more about the domestic cat. Their history is really interesting, and I bet that there even more to find out. It’s just a shame that they are considered to be the only group of the Felidae species that is not currently endangered or threatened. 

 

O’Brien, S. J., W. Johnson, et al. (2008). “State of cat genomics.” Trends in Genetics 24(6): 268-279.
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