Imagine this. You're at the checkout counter, being billed for those edibles you've grabbed for your first (socially distanced) gathering in ages, when your card is rejected. Panic ensues, but then you dig your hands into your pocket, and it jingles reassuringly — not with coins, but sea shells! The bill is settled, and the day saved. In some villages of Papua New Guinea, this could well be real. Currencies have evolved spectacularly across time and space. And around the world, the more creative ones have existed long before, and after, banknotes and coins took center stage. But what’s next? Today, we check out alternative currencies that have paved the way, and some that could diversify the future of trading.