We use an alternative proxy, actually alternatives proxy. This was existing data. According to archaeologists identified 20 different points in the world in which farming started. We didn't start in one point and spread everywhere. There did 20 centers of domestication. What our data shows is that what really matters for the emergence of hierarchies proximity to a center of domestication does not matter. Simply have no positive effect on the proximity to roots and tubers do not have an effect. And we ask what explains these findings, and the answer is serious, not land productivity. Places that better available are very similar to places that only roots and tuber are available. That's exactly the theory we discussed earlier that
Since at least Adam Smith, the common wisdom has been that the transition from hunter-gathering to farming allowed the creation of the State. Farming, so went the theory, led to agricultural surplus, and that surplus is the prerequisite for taxation and a State. But economist Omer Moav of the University of Warwick and Reichman University argues that it wasn't farming but the farming of a particular kind of crop (but not others) that led to hierarchy and the State. Moav explains to EconTalk host Russ Roberts storability is the key dimension that allows for taxation and a State. The conversation includes a discussion of why it's important to understand the past and the challenges of confirming or refuting theories about history.