Garfield, star of the eponymous comic strip created by Jim Davis in 1978, is, like many of the cats that roam our homes, orange. He is orange in the same way that some people are redheaded, some horses are brown, or some dogs are Irish setters, but there is one important difference.

For all other animals, including redheaded humans, we know what causes this characteristic colour, but surprisingly, we didn’t know what causes it in cats – and felines in general – until now.

Two papers have just been published on bioRxiv – one of the most popular pre-publication repositories of unreviewed articles – that explain the genetics behind orange cats. One comes from Greg Barsh’s lab at Stanford University, California. The other is from Hiroyuki Sasaki’s lab at Kyushu University, Japan.

Mammals have only two pigments, which are two colours of melanin: eumelanin (dark brown, blackish) and pheomelanin (yellowish, reddish or orange). Redheads only produce pheomelanin, while dark-skinned people accumulate mainly eumelanin. All other skin and hair colours fall somwehere in between, thanks to as many as 700 genes that regulate pigmentation in animals.

In primates,........

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