Around 8,000 years ago, a poisonous Peruvian tuber was rendered edible via a still-baffling process that involved reducing glycoalkaloid levels by 15-25 fold. Even now, these poisons are present in the potato, particularly the varieties Home Guard, Rocket and British Queen, until the tubers reach maturity. The result of this domestication was an edible plant, or esculent, that has come to dominate the world.
Its importance was celebrated by the Moche civilisation of northern Peru, whose ceramics in the form of "a head or face of the potato" sound like a precursor to Mr Potato Head.
Packed with vitamins (100g of mash provides half of the recommended daily allowance of vitamin C); non-fattening (it's the fats involved in preparation that cause problems); and exceptionally productive (we can eat three-quarters of its biomass compared to one-third with grain), the spud is astonishingly rich in nutrition. People have lived active lives for months on a diet solely consisting of potatoes, though this involves a daunting intake of two to three kilos per day.
"Sadly," notes John Reader, "the innocent potato has facilitated exploitation wherever it has been introduced." Spanish silver from Peru depended on deadly mercury mines, where a slave workforce was fuelled by potatoes. And when the potato arrived in the Old World in 1562 – not via Drake or Raleigh, whose voyages didn't touch potato-growing regions – it was considered aphrodisiac. It spread was largely due to the European wars of the 18th century. When soldiers stole their grain, peasants could survive on a food store hidden in the ground.
Dependency on the potato achieved disastrous apogee in Ireland in 1845-46, when the crop, mainly an unpalatable variety known as lumpers, was afflicted by late potato blight. Constantly mutating into more resistant strains, late blight is again "the world's worst agricultural disease". As a result, the potato is the most chemically dependent crop.
In a book sometimes too wide-ranging – it is strange to find oneself reading about the Battle of Stamford Bridge in 1066 – there's one strange omission: Reader isn't very interested in the culinary side of the potato. You will search in vain for delicious gratin dauphinois or toothsome colcannon. And though he takes us to Papua New Guinea and China, since 1993 the leading producer of potatoes, his reference to "the Rochdale district of Yorkshire" suggests the north of England remains terra incognita.
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