They’re one of the world’s most important food crops and delicious roasted, mashed or fried, but the exact genetic origins of the humble potato have long been something of a mystery to scientists.

Now, researchers say the modern-day potato evolved from hybridization of the ancestors of tomato plants and another potato-like plant, known as etuberosum, in South America up to 9 million years ago. The hybridization created the petota lineage — which includes the cultivated potato seen in supermarkets around the world, as well as 107 wild potato species.