If you google 'oldest known vegetable' you will get scads of 'trivia' and 'useless facts' pages stating it is the pea. I don't think very highly of these sites because they all copy off each other, and none cite sources.
Anyway, here's an alternative:
Dear Dr. Universe,
What is the oldest known vegetable?
I posed your question to Larry Hiller, a WSU Horticulture professor. This is what I found out.
There is not one specific vegetable that we can find that is positively the oldest. Lettuce, onions, and garlic are among the first vegetables documented, and date back to 500-1000 BC. These vegetables are mentioned in many ancient books, one being the Bible. However, through science, it has been proven that potatoes are also very old and date back to 500-1000 BC, but there is no written documentation of this. So, we may never know the very first or oldest vegetable, but can see that many of the vegetables we eat today also fed the people of ancient times.
Sincerely
LeAnne Strickler, future teacher helping Dr. Universe
http://www.wsu.edu/DrUniverse/vege.html
[From wsu.edu 2003 article, no longer online]
