Legend tells us that black cats are unlucky.

Black cats have a tainted reputation. Some people think of them as bad luck, which is why they are so common at Halloween. But if black cats are so bad, why are they so common in nature?

Stephen O’Brien, chief of the Laboratory of Genomic Diversity at the National Cancer Institute, found that there are at least four different genetic changes that cause the cats’ black coats. “We had one genetic mutation in one gene in the domestic cat, and a different one in the jaguars. And we actually found a third in the jaguarundi. The genetic basis of the black coat was different in all three species.” That means the mutations showed up independently on each lineage of cat, which indicates that black-coated cats were repeatedly favored by evolution.

Scientists are still not sure why the black fur mutation is so common, especially since the black fur gene is a recessive gene, which means a cat must carry two copies of it in order to be black. One idea is that it provides camouflage at night, but strong beasts like leopards and jaguars don’t really need this kind of protection. So O’Brien thinks the mutation may have to do with health. He found that the black coat mutation in the jaguar and jaguarundi affects a gene in a family of proteins called seven-transmembrane receptors. Viruses often use these receptors to get inside cells, and it is thought that HIV might be one of those viruses. A mutation in this gene might provide resistance to diseases caused by those viruses.

Because cats get a lot of the same diseases we do, such as cancer, Alzheimer’s disease, multiple sclerosis, and AIDS, figuring out how cats evolved to resist disease could give scientists insights into treating the same ailments in people. “Perhaps we could get a better handle on some of the natural defenses that the animals have used,” says O’Brien, “animals that don’t have hospital rooms or HMO’s or pharmacies to treat their ills, how they have adapted using natural selection and spontaneous genetic mutations to defend against some of the same diseases that humans have today.”

Source: ScienCentral News