There is a possible explanation for why gold has been a base of currency.
IF, as a counter-example, you bring something like a slab of beef as the item you trade to get something else - like maybe a really good knife or spear point - congratulations, you just entered a "barter" economy. But one problem with that is the ephemeral or consumable nature of the bartered goods. The other, of course, is determining what constitutes a fair trade.
On the other hand, because you DON'T eat gold and it doesn't wear out (at least, not in people's lifetimes), it is a durable entity that can become a SYMBOL of what you have to be traded. Gold is too soft for making decent weapons, so it is inappropriate as an actual traded item for its own value - or at least that was true until the goldsmiths learned to make jewelry. Lump iron and steel have usefulness in making things, so they wouldn't be appropriate as an exchange medium; they have other, better uses. Copper and bronze are also relatively soft, plus there is usually lead in copper (the ores frequently occur near each other) which makes them poisonous, long-term. Technology had to develop (a lot, in some cases) in order for other metals to become useful. Gold, being relatively inert, because the standard for that symbol of value.
Once mankind developed the idea of an abstracted or symbolic measure of value, it would follow that they needed something as a medium of exchange as an accounting artifice - though they might not have called it "accounting" when it was first started. It was just "counting" then. We started with counting shells and pretty rocks, but we graduated from that LONG ago. But eventually, the idea of durable symbols of value made it easy for folks to carry those symbols rather than actually carrying trade goods.
If you have established an exchange rate - which in this context would look like a grocery store ad - you would have knowledge of how many grams of gold it took to buy that slab of beef mentioned earlier.