US scientists have found that all modern varieties of potatoes can be traced back to a single source – a potato grown in Peru over 7,000 years ago. The team, led by Dr David Spooner of the University of Wisconsin-Madison, who spends two months a year collecting wild potatoes on treks in South America’s mountainous regions analysed the DNA of about 360 potatoes, both wild and cultivated. Dr Spooner said archaeological finds had shown potatoes were being grown in Peru by farmers “more than 7,000 years ago”. Potatoes were brought back to Spain by the conquistadors around 1570, and spread throughout Europe. They were later introduced in North America by British colonists.