Money has been swappable for food at every point in human history (except stranded on a deserted island scenarios), so it's a great assumption to make. Besides, nobody said if you have money/currency you can't know how to produce your own food. Having knowledge of food growing may save your life in one scenario, but savings might save your life in another. I have spent the past 20+ years adding to my understanding of both. I think another 200 years on each and I'll have a decent working knowledge :P