http://messybeast.com/urbancat2.htm
THE BLIND COAL MINE KITTIES
There is a leganed that cats were thrown down closed coal mines in England during the Thatcher years by cruel people wanting to dispose of their pets. According to the story, many years later, it was found that the cats had survived the fall and had mutated into a community of blind cats with huge ears. This large-eared, blind cats with good hearing had allegedly adapted to living in the complete darkness of the mine shaft. The same motice is used by Akif Pirinçci in his "Felidae" novels except that the cats are thrown into the sewers. There, they hunt rats, rescue other discarded kittens and evolve into blind cats with exceptional hearing. The problem for both the mine-shaft myth and the sewer-myth is that the evolution of sightless cave-dwelling cats would take many generations unless the original cats had a genetic form of blindness that they passed on to their descendents.
In part, this myth relies on the fact most of us have heard of eyeless animals living in caves. Those animals evolved from sighted individuals over hundreds of generations rather than a mere 30 years (Thatcher's Britain being the late 1970s and the 1980s). There would not be time for the cats to evolve into a whole new species. Secondly, while the sewer cats would have rats and mice to hunt, there is not a lot living in a mineshaft that a cat could hunt. If not too contaminated, they might support ecosystems similar to deep caves - invertebrates, insects - but not enough to support a food chain with a cat at the top of it.