It seems that black cats were an unlucky bystander of the spread of Christianity throughout Europe in the Middle Ages. Cats have long been associated with pagan customs and old gods, such as the Egyptians and the Roman goddess Diana. Christianity demonised the existing religion or altered pagan festivals to celebrate Christian themes.
When Pope Gregory IX declared black cats to be the incarnation of the devil in 1233 AD, Christians killed black cats at village festivals to punish them for their supposed devilish ways. By the 14th century, cats were nearly extinct in Europe.
Over the next few centuries, black cats were thought to be in league with witches as their ‘familiars’, or were even witches in disguise. Just owning a black cat during the witch trials of the 16th and 17th centuries was enough to condemn a ‘witch’ to death.
Even now, black cat superstitions still linger – a black cat crossing your path is considered unlucky. However it's generally the cats themselves that suffer bad luck. Research has shown that it takes four to six days longer for black shelter cats to be adopted than cats of any other colour. As every cat owner knows, the only unlucky thing about a black cat is you can’t see them in the dark, which often means you trip over them on a midnight run to the bathroom.
In some countries, particularly in Asia, black cats are thought to help you be lucky in love and wealth. In Japan single women who own black cats are believed to have more suitors, and in the English Midlands, a black cat is seen as in ideal wedding gift for the bride. In Scotland, a black cat arriving on your doorstep signals prosperity and good luck. Especially for the cat.