Many plants came under human cultivation by the unsophisticated but slowly effective means of gathering useful plants and leaving a few seeds in fertile refuse heaps. Judging from archaeological evidence, early Europeans seem to have relied on wheat, fava beans, peas, turnips, onions, radishes, and cabbage. In Central America, corn, beans, hard squashes, tomatoes, and avocados were staples around 3500 BCE, while Peruvian settlements relied heavily on the potato. Northern Asia started with millets, cabbage relatives, soybeans, and tree fruits in the apple and peach families; southern Asia had rice, bananas, coconuts, yams, cabbage relatives, and citrus fruits. Indigenous African crops included related but distinct millets, sorghum, rice, and bananas, as well as yams and cowpeas. Mustard seed flavored foods in Europe and in Asia, where ginger may also have been used. Chilli “pepper” was probably the chief spice in the Americas.