Five thousand holes run for nearly a mile along a mountain in Peru's Pisco Valley.
They're arranged in rows, with gaps separating one group from another. Researchers spent decades trying to explain them. They were proposed as graves, defensive structures, water collectors and storage pits.
More recent work suggests something more ordinary was happening there.
People were trading.
Farmers from the valley, fishing communities from the coast and travelers from the highlands could bring things produced in very different environments into the same place. Grain, cotton, peppers, dried fish and other goods could be placed into the holes, counted and exchanged.
That explains the holes.
The gaps may be more interesting.
People needed room to move between the rows. Once they're there, they're also standing among people who came from somewhere else and know different things.
A person might arrive looking for cotton and leave with cotton, some news and a relationship that didn't exist that morning.
The transaction gave people a reason to meet. The meeting created possibilities that weren't contained in the transaction.
We usually describe trade in terms of what moves between people. I have something you want. You have something I want. We agree on terms and exchange them.
That's useful because the difference between us is real.
The farmer knows things about the valley that the traveler doesn't. The traveler knows the road. Someone arriving from the coast has encountered people, conditions and information unavailable inland.
Different goods are only part of what has arrived at the market.
Adam Smith noticed that something larger could emerge from ordinary exchanges among people pursuing their own interests. A baker doesn't need to understand the entire town in order to help feed it. Enough local decisions interacting with one another can produce an order nobody individually designed.
Economics became very good at describing part of this. Prices carry information. Supply changes. Demand responds. Goods move.
Yet a marketplace contains relationships that aren't represented by the price of anything.
Some of those relationships eventually produce transactions. Others produce friendships, arguments, marriages, rumors, opportunities, warnings, shared knowledge or nothing particularly memorable at all.
The distinction matters because we can improve one part of a system while accidentally removing another.
If the only purpose of a marketplace is moving goods efficiently, the gaps start looking wasteful.
Why travel there at all? Put the inventory in a database. Match buyers with sellers. Automate payment. Optimize delivery.
For many transactions, that's an improvement. I don't need to develop a meaningful relationship with someone every time I buy socks.
Something changes, though, when every unnecessary encounter is treated as inefficiency.
We don't just remove waiting. We remove opportunities whose value couldn't have been known before the encounter happened.
This happens outside markets too.
Most conversations have some identifiable purpose. We need information, help, a decision, an answer or simply a little company. The conversation does what it needed to do and ends.
Occasionally, a conversation goes somewhere neither person expected.
That usually requires some real difference between the people involved. If we already know exactly what the other person will say, there isn't much available to discover. If one person simply overwhelms the other, there isn't much available there either.
The interesting case is when the difference survives the encounter.
I can hear what you're saying without immediately converting it into something I already believe. You can do the same with me. Neither of us has to surrender our position merely to keep the conversation moving.
That creates an uncomfortable intermediate state.
We haven't agreed.
We haven't necessarily disagreed either, because we may still be figuring out what the d