According to Isle of Man records,[weasel words] the taillessness trait of the Manx (and ultimately the Cymric) began as a mutation among the island's domestic cat population. Given the island's closed environment and small gene pool, the dominant gene that decided the cats' taillessness was easily passed from one generation to the next, along with the gene for long hair. Long-haired kittens had been born to Manx cats on the Isle of Man, but had always been discarded by breeders as "mutants". Then, in the 1960s, similar kittens were born in Canada and were intentionally bred. This was the start of the increase of Cymric popularity. It took many years for the Cymric to be recognized as a breed of its own by cat associations. The Manx was recognized in the 1920s, but the Cymric was not shown until the 1960s and did not begin to gain popularity until the mid-1970s.
The Fédération Internationale Féline (FIFE), World Cat Federation (WCF), American Association of Cat Enthusiasts (AACE), Canadian Cat Association (CCA-AFC), and Australian Cat Federation (ACF), New Zealand Cat Fancy (NZCF), Southern Africa Cat Council (SACC), American Cat Fanciers Association (ACFA, of the US East Coast), and Cat Fanciers' Federation (CFF, in the US Northeast) consider the Cymric a separate breed. The Cat Aficionado Association (CAA) of China does also, by virtue of the CAA having adopted all the breed standards of its Western partner, ACFA; it is unknown if any Cyrmic breeders are actually in China.
The International Cat Association (TICA) recognizes the Cymric by that name but as a variety of Manx, not a separate breed with its own standard. Also simply covering it in their Manx breed standards, the US-based Cat Fanciers' Association (CFA), the Co-ordinating Cat Council of Australia (CCCA), and the UK's Governing Council of the Cat Fancy (GCCF) recognize the variety as the long-haired Manx rather than Cymric (the CFA and CCCA call it the Manx Longhair, while GCCF uses the term Semi-longhair Manx Variant). The ACF formerly took this route, calling it the Longhaired Manx, but recognized it as a separate breed at the beginning of 2015, using the GCCF Manx standard (aside from coat length).
Feline Federation Europe (FFE) does not recognize the breed or sub-breed at all, under any name, as of March 2013.