There are 270,000 plant species in the world. There are between 1000 and 2000 EDIBLE to humans plant species. Within the species there are thousands of varieties. For example in 2014 there were 1600 varieties of bananas. There are/were more than 2000 varieties of plums. Among the top 15 food species are soybeans, peanuts, rice, wheat, bananas. How long would you have to live to taste every variety of every species of edible-to-humans plants? Further complicating things. New varieties are being created all the time. I wonder what the first species and variety of the first plant humans consumed? They probably stuck to eating other animals first.