If interest rates matter to you, and you have an inquiring mind, pick up a copy of Sydney Homer's A History of Interest Rates. (The latest editions were co-authored with Richard Sylla and include more recent developments, but I treasure my first edition autographed copy.)
Here's the opening paragraph:
In historic times credit preceded the coining of money by over two thousand years. Coinage is dated from the first millennium B.C., but old Sumerian documents, circa 3000 B.C., reveal a systematic use of credit based on loans of grain by volume and loans of metal by weight. Often these loans carried interest.