According to the Moreveg website, the oldest known vegetable is the pea, because it has been found in Stone Age settlements over 8,000 years old. Vegetables have been heavily cultivated by humans, and the vegetables eaten in modern times differ greatly from their predecessors. Ancient man also ate plants that modern man would not usually consider vegetables, like ferns and cattails.
Slate reports that kale, cabbage, broccoli, cauliflower, Brussels sprouts and kohlrabi were all cultivated from the same prehistoric plant between 8,000 and 10,000 years ago. "Wild carrots may predate human agriculture, but they’re unpalatable and look nothing like the cultivated variety." The orange carrot known in modern times did not exist until the 17th century.
In contrast, many modern fruits have ancient counterparts. Olives, plums and pears were found in northern Israel from the Paleolithic era. Dates were found in the teeth of a 40,000-year-old Neanderthal. Grapes were found in northeastern Tennessee that appear to be 7 million years old. According to Slate, "Apple trees blanketed Kazakhstan 30,000 years ago, oranges were common in China, and wild berries grew in Europe." The fruit available has evolved less drastically than vegetables, but has still been modified somewhat. "Selection by humans has made them larger and sweeter, and may have caused other chemical changes."