By A.L.

CARROTS used to be white. They were grown for their leaves and seeds, much as their distant relatives, parsley and coriander, still are. The chemical compounds that give carrots their vivid colour, carotenoids, are usually used by plants that grow above ground to assist in the process of photosynthesis. But carrots live underground. Subterranean cousins, such as the parsnip and the turnip are both mainly white. How then did the carrot bring a bit of colour to the dinner table?

Carrots originated in modern-day Iran and Afghanistan. They contain around 32,000 genes (more than humans), of which two recessive ones contribute to a build-up of carotenoids, such as alpha- and beta-carotene. Scientists believe early farmers grew colourful carrots unintentionally, and then continued the practice more purposefully in order to differentiate them from wild ones. Around 1,100 years ago purple and then yellow varieties emerged, followed another 600 years later, thanks to further selective breeding, by the modern orange form, which has lots of beta carotene.

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