eli5: Why does it seem like every civilisation uses coins as currency even before there was a lot of mingling?

Question

I just saw a photo of old coins from like 1 or 2000 years ago and they are all round.
Why is it that they all use coins and not squares or something else completely?

In: Other

Answer 1

There is a wikipedia page for this! https://en.wikipedia.org/wiki/Coinage_shapes

Short answer: it was not always a circle, for example “Many countries have struck square coins with rounded corners. Some of these, such as the Netherlands zinc 5 cent coin of World War II (1941–1943)[4] and the Bangladesh 5 poisha coin (1977–1994)[5] ”

If you look further in the past, you can see that it was not that round at first: https://en.wikipedia.org/wiki/Coin. But it’s an easy shape to obtain when you either drop some melted metal on a surface, or hit with a hammer on a ductile metal.

That said, Mauryan Empire coins, 3rd century BC, were square coins as well as Bilingual coin of Agathocles of Bactria with Hindu deities, c. 180 BC

Also, rectangular bar of metal that you can cut in was precursor of coins. But it’s nor really “a coin” I would say.