What do Garfield, Heathcliff and Puss in Boots have in common? They’re all cats, they’re all orange, and they’re all males. This is no accident. As it turns out, most orange cats are male, while almost all calicos and tortoiseshells are females. This difference in hair color has puzzled scientists and cat lovers for decades, until now. A team led by Stanford geneticist Greg Barsh has uncovered the genetic mutation responsible for orange fur. Orange coloring comes from a gene called Arhgap36, found on the X chromosome. Since males only have one X chromosome, they express this mutation fully, leading to their signature fully orange coats. Female cats, with two X chromosomes, end up displaying a mix of colors, creating calicos and tortoiseshells. What makes this discovery especially exciting is that the gene wasn’t previously known to influence pigmentation. This breakthrough also sheds light on feline genetics and could even help trace the history of orange cats. Some evidence suggests their fiery coats may date back to ancient Egyptian mummified cats.
