Full text: https://substack.com/home/post/p-193665596
A quantitative analysis of ancient DNA and archaeological stage
Ancient DNA contains a surprise. When researchers extract polygenic scores linked to educational attainment from prehistoric skeletons, the scores rise through time. Hunter-gatherers score lower than early farmers, early farmers lower than Bronze Age populations, and so on. The standard interpretation is that this reflects something about the passage of time itself such as selection, migration, demographic turnover, or some mixture of all three.
But time is not the only thing changing across that span. Social and technological complexity are changing too. A Paleolithic forager band and an Iron Age kingdom are not just separated by millennia. They are separated by farming, writing, cities, specialization, storage, hierarchy, and the entire accumulated weight of what we loosely call civilization. So here is the question worth asking: when those polygenic scores rise through ancient history, are we really just watching a clock tick or are we watching something track the emergence of more complex ways of organizing human life?
Using ancient individuals from the AADR dataset, I assigned each archaeological period a civilization-stage score and asked whether that score predicts educational-attainment polygenic scores even after controlling for absolute date. In practice, that meant coding Paleo-Mesolithic groups as 1, Neolithic groups as 2, Copper Age groups as 3, Bronze Age groups as 4, and Iron Age groups as 5.
The leverage comes from a basic fact of world prehistory: civilization and chronology do not move in lockstep. Greece had farming millennia before Britain. Some populations at the same date occupied very different social worlds. That mismatch is what makes it possible to pull the two apart and ask which one is actually doing the work.
A time trend by itself could reflect selection, migration, demography, drift, or some mixture of all of them. The harder question is whether the relevant axis is not just time, but civilization.
If you take two ancient populations from different social worlds, but do not let chronology do all the explanatory work, does their place on the civilizational ladder still matter?
The modern world has made one thing hard to miss. Cognitive performance, schooling, institutional complexity, and economic development cluster together. But once we move back into deep history, the picture becomes much hazier. We still know remarkably little about whether the genetic variants associated with educational attainment track not just the passage of time, but the emergence of more complex forms of social organization.
