> This was fuelled by what is known as moka, a system of competitive gift giving, where you give someone in your tribe goods like a pile of pigs and shells, and they are then obligated to give you back more later, and you them more again after that. Whoever gives the most, publicly, becomes the big man.

This reminds me of the Reciprocity and Re-Distribution system in the Inca Empire. There wasn't a system of currency or markets. But there was an Ayni (mutual aid) and Minka (collective work) system, paired with a Mita system: work done for the Sapa Inca which was in return "paid" by the Sapa Inca in feasts, food and goods/gifts. This was all glued together by the concept of Ayllu (family), where these obligations were established through family connections and of course the Sapa Inca had marriage connections with subordinate chiefs.

I myself can't stop thinking about the Inca Empire Economy and how it shows in reality that currency is not about the paper nor number nor symbols, and more about the "I owe you"s that move in the economy.