The article covers how it started. If you are in currency-less barter only hunter gatherer society, it is not yet a medium of exchange. You would have better luck trading with food than anything else in those societies, as covered in the article.
Also diamond wasn't and still isn't used as a currency. Only in the last 10 years, it became a somewhat semi-serious investment grade material.
Also diamond wasn't and still isn't used as a currency. Only in the last 10 years, it became a somewhat semi-serious investment grade material.